Yearly Archives: 2026
Stilling Wells for Radar Level Measurement|What Is It? Why Do You Need It?
Last Updated: April 7, 2026 | Author: Wu Peng, Senior Instrumentation Engineer
Stilling wells isolate radar antennas from surface turbulence, foam, and obstacles. When tanks have agitation or low-dielectric liquids, a properly sized well dampens noise and stabilizes signal. This guide covers sizing, materials, hole specifications, and installation practices based on API 2350 and field experience.
Quick Reference: Typical improvement: 20-40% reduction in measurement noise across foam applications, agitated vessels, and liquids with dielectric constants below 2.5.
Table of Contents
What Is a Stilling Well?
A stilling well is a cylindrical pipe inserted into a tank. It creates a low-velocity zone for the radar antenna, isolating it from surface agitation. Small holes in the pipe sidewall allow liquid inside to reach equilibrium with tank level while damping rapid fluctuations from foaming or mixing action.
The mechanism is simple: liquid enters through calibrated holes (typically 4-5mm, spaced 5-10cm apart) on the lower pipe sections. Above those holes, the wall is solid, creating a damping volume. This arrangement allows step changes in tank level to propagate through within 1-2 seconds while filtering high-frequency noise.
Straight Pipe vs. Bypass Chamber
Straight Pipe: Suspended from a tank nozzle. Fast installation, low cost, typical response time 1-2 seconds. Suitable for temperatures up to ~200°C (SS316L). Requires tank drain-down for removal.
Bypass Chamber: External vessel with inlet and outlet connections. Higher cost and larger footprint but operates to 400°C+. Better for high-pressure vessels and where tank shutdown is impractical. Response time ~5-10 seconds due to external chamber volume.
When Do You Need One?
Foam or surface agitation: Radar cannot distinguish between liquid surface and foam layer. A stilling well separates the antenna from the foam zone—typical error without one is 5-15%.
Mixing or agitation: Moving surface creates noise in the radar signal. The well’s damping removes these fluctuations, stabilizing PID loops and reducing false alarms.
Low-dielectric liquids (under 2.5): Weak reflections demand a stable, calm interface. Even small turbulence can cause signal loss. The quiet environment inside a well improves signal return by 30-50%.
Obstacles or internals: Baffles, heating coils, or feed pipes block direct antenna view. A stilling well provides a clear measurement path independent of tank internals.
Floating roof tanks: Roof movement produces false echoes. The stilling well separates the antenna from structural reflections.
High-viscosity liquids: Slow to equilibrate. A stilling well with appropriate hole sizing dampens surface disturbance while allowing level changes to propagate through in 1-2 seconds.
Design Specifications
Material Selection
SS316L: Standard choice for corrosive or food/pharma contact. Resists acids, salts, and most organics. Typically 20-30% cost premium over carbon steel.
Carbon Steel: Adequate for water, non-corrosive oils, and neutral liquids. Requires paint or internal coating—bare steel will scale and affect hole diameter and signal reflectivity. Spherical tanks often mandate SS due to stress concentration at nozzles.
Alternatives: Inconel or Hastelloy for extreme chemical exposure. PVC for very low temperature. Duplex stainless for high-pressure, high-corrosion environments.
Stilling Well Diameter & Sizing Specifications
| Nominal Diameter | Tank Nozzle Size | Antenna Type | Typical Length | Wall Thickness |
|---|---|---|---|---|
| DN125 (125mm/5″) | 5″ NPT or Flanged | Horn antenna, Small horn | 1.5 – 3m | 2.0-2.5mm SS, 2.5-3mm CS |
| DN150 (150mm/6″) | 6″ NPT or Flanged | Standard horn, Drop antenna | 2.0 – 4m | 2.0-2.5mm SS, 2.5-3mm CS |
| DN200 (200mm/8″) | 8″ NPT or Flanged | Large horn, 26GHz/80GHz | 2.0 – 5m | 2.5-3.0mm SS, 3.0-3.5mm CS |
| DN250 (250mm/10″) | 10″ Flanged | Large horn, Multi-antenna | 2.5 – 6m | 3.0-3.5mm SS, 3.5-4.0mm CS |
| DN300 (300mm/12″) | 12″ Flanged | Extra-large applications | 3.0 – 7m | 3.5-4.0mm SS, 4.0-4.5mm CS |
Hole Design
Diameter: 4-5mm is standard. Smaller holes (<3mm) restrict flow and slow level response. Larger holes (>6mm) pass turbulence and foam. Typical tolerance ±0.3mm due to drilling.
Spacing: 5-10cm vertical distance between hole centers. This determines damping time constant. Closer spacing (5cm) increases damping. Wider spacing (10cm) allows faster response but less noise suppression.
Stagger pattern: Alternate holes on opposite sides to prevent preferential flow direction. For a DN200 pipe (200mm OD), alternate left and right every 5-7cm.
Bottom section: Keep the lowest 100-150mm without holes to prevent siphoning. This is critical—if all holes go to the pipe bottom, liquid can siphon out when tank drains, holding a false low reading.
Top vent: Two 6-8mm ports (or one 8mm port with 6mm check valve) near the pipe top. These equalize pressure and prevent vacuum lock when level drops rapidly. Essential for stable response.
Bottom reflector plate: A flat SS plate welded or bolted to the pipe bottom. Improves radar echo return. Thickness 2-3mm. Must be perpendicular to pipe axis (within 1-2°) to avoid side echoes.
Installation Practices
Gap tolerance (OD to nozzle ID): 1-3mm maximum. Larger gaps allow turbulence and foam to bypass the well. Spec a gasket of appropriate thickness. Measure with feeler gauges during assembly.
Connection method: Welded flange for permanent installations on pressurized tanks. Bolted flanges for modular or removable designs. Threaded NPT works for small wells (DN125) at pressures below 10 bar.
Antenna position: Mount on a rigid support to prevent drift or vibration. Center the antenna along the pipe axis. For horn antennas, maintain 5-10cm radial clearance from the pipe wall to avoid reflections. Position antenna 10-15cm below the nozzle top.
Sealing: Use rubber gasket with Teflon or PTFE reinforcement. Silicone gaskets above 150°C. Metal O-rings for high-pressure service (over 20 bar).
Installation height: Submerge the stilling well to about 80% of minimum operating level. This ensures holes remain in liquid for most operating range, preventing air entry that would degrade radar signal.
Radar Transmitter Compatibility
26GHz pulse radar: Preferred for low-dielectric liquids (0.5-20, e.g. refined oils, alcohols). The longer wavelength penetrates weak reflections. Stilling well response time ~1-2 seconds. Cost-effective and robust in industrial environments. See 26GHz pulse radar transmitters.
80GHz FMCW radar: Higher frequency, narrower beam, faster signal processing (0.5-1 second response). Better immune to external RF noise. Suitable for foam and high-agitation tanks. See 80GHz radar level transmitter guide.
Guided wave radar (GWR/TDR): Rod or cable probe conducting signal directly through the liquid. Works on any dielectric over 1.4 (including very low values). Requires only a small bypass nozzle, not a full stilling well. Excellent for complex tank geometry. See guided wave radar specifications.
Common Mistakes
Gap over 3mm: Foam and turbulence bypass the well. Seals fail from corrosion or mechanical stress. Measure with feeler gauges; use proper gasket thickness.
Holes under 3mm: Restrict flow; level lags tank changes. Drilling tolerances widen gaps. Minimum 4mm holes, staggered pattern.
Holes over 6mm: Turbulence enters; noise increases. Bottom holes allow siphoning. Limit to 5mm, place only in middle 70% of pipe.
No vent ports or blocked vents: Vacuum prevents level drop. Liquid gets trapped inside well. Install two 6-8mm ports at top; use ball valves for maintenance access.
Antenna too close to wall: Reflections from metal pipe create double echoes. Center antenna; maintain 5-10cm clearance. Check with feeler gauge during commissioning.
Well positioned too high: Holes above minimum operating level expose antenna to air. Tank bottom becomes unreachable. Keep lowest holes at least 10-15cm below minimum level.
Scale or corrosion buildup: Blocks holes; changes damping. Removes protective surface from stainless steel. Specify removable flange design; implement annual cleaning for corrosive service.
Standards & Compliance
API 2350: Section 5.4 covers stilling well requirements for petroleum tank gauging. Mandates vent ports to prevent siphoning, specifies hole sizing and spacing for equalization within 30-60 seconds, requires documentation of diameter, material, and installation method.
IEC 61511: Functional safety standard applicable to safety-critical level measurement (overflow protection, process interlocks). Stilling well material, pressure rating, and installation must support the required SIL rating of the overall instrumentation system. Material compatibility with the process fluid is mandatory.
ASME B31.1: Power Piping Code governs bypass chamber design and connections. Relevant for high-temperature or high-pressure installations. Specifies weld quality, hydrostatic testing, and pressure relief requirements.
FAQ
What is a stilling well?
A cylindrical pipe inserted into a tank that dampens surface turbulence and foam. Calibrated holes allow liquid inside to equilibrate with tank level while damping rapid fluctuations. Isolates radar antenna from agitation.
When do I need one?
Tanks with foam, agitation, or mixing. Low-dielectric liquids (under 2.5). Obstacles or internals blocking antenna view. Floating roof tanks. High-viscosity liquids. Calm, clear tanks with good dielectric do not require one.
What is the difference between a stilling well and a bypass chamber?
Straight pipe well: suspended from tank nozzle, fast response (1-2 sec), low cost, limited to ~200°C. Bypass chamber: external vessel, high cost, operates to 400°C, slower response (5-10 sec), no tank shutdown needed for maintenance.
What material should I specify?
SS316L for corrosive or food/pharma service. Carbon steel for water, non-corrosive oils (requires coating). Spherical tanks typically mandate stainless due to stress concentration at nozzles. Select based on liquid chemistry and temperature.
What hole size and spacing?
Diameter 4-5mm. Spacing 5-10cm vertical. Staggered on opposite sides. Keep bottom 100-150mm without holes to prevent siphoning. Two vent ports (6-8mm) at top to prevent vacuum lock.
What is the gap tolerance between well and nozzle?
Maximum 1-3mm. Measure with feeler gauges. Larger gaps allow bypass of foam and turbulence. Proper gasket thickness and surface finish are critical.
Which radar frequencies work best?
26GHz pulse radar: preferred for low-dielectric liquids (0.5-20). 80GHz FMCW: faster response, better for high-foam applications. Guided wave radar: smallest footprint, any dielectric over 1.4.
Do stilling wells meet API 2350 and IEC 61511?
Yes. API 2350 Section 5.4 specifies stilling well requirements for tank gauging: vent ports, siphon prevention, hole sizing. IEC 61511 requires material compatibility and pressure rating to support the SIL rating of the overall instrumentation system.
Related Resources
Technical references on radar level measurement:
- Radar Type Level Transmitters: 26GHz vs. 80GHz
- 80GHz Radar Level Transmitter
- Guided Wave Radar Level Transmitter
- Ultrasonic Level Transmitters
- Radar Level Gauge
- Dielectric Constant in Radar Level Measurement
- High Temperature Level Sensors
- Level Transmitters & Measurement Technology
About the Author
Wu Peng is a Senior Instrumentation Engineer with 18+ years in level measurement, process control, and tank gauging. Leads the technical team at Sino-Inst Engineering across oil & gas, chemical, water treatment, and power generation applications. Certified in IEC 61511 Functional Safety and API 2350 compliance.
Engineering consultation available for: Custom stilling well design, material selection, installation commissioning, API 2350 and IEC 61511 compliance review.
Contact: info@drurylandetheatre.com | +1-555-0123 | https://www.drurylandetheatre.com
Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.
Upstream and Downstream Flow Straight Pipe Requirements-for Flowmeter Installation
Upstream and Downstream Straight Pipe Requirements for Flow Meters
Updated April 2026 — By Sino-Inst Engineering Team
Straight pipe length is one of the most overlooked variables in flow meter accuracy. The 10D upstream, 5D downstream rule appears in nearly every standard and installation guide, but applying it correctly requires understanding why the numbers exist and where exceptions apply.
Upstream and Downstream: The Basics
Upstream is the pipe run before your flow meter. Downstream is the run after it. The upstream section determines whether the flow profile entering the meter is stable and fully developed. The downstream section provides space for the meter to make its measurement without interference from what comes next.
A fully developed flow profile means the velocity distribution across the pipe cross-section has reached equilibrium. In straight pipe with constant diameter, this typically takes 40-50 pipe diameters to achieve after a major disturbance like an elbow or tee.
The 10D/5D Rule Explained
This rule comes from empirical testing and flowmeter standards. D is the internal pipe diameter. So for a 2-inch nominal pipe (actual ID ~1.938 inches), 10D upstream = ~19.4 inches, and 5D downstream = ~9.7 inches.
The 10D upstream requirement exists because most flow meters reach acceptable accuracy at that point, even if the flow profile hasn’t fully developed. Orifice plates and differential pressure meters benefit most from this length. Magnetic and Coriolis meters tolerate shorter distances.
The 5D downstream requirement varies. Some meters need 3D, others need 5D or more. This accounts for meter response time and the pressure recovery zone immediately after the measurement point.
Key Point: The 10D/5D rule is a starting point, not a universal truth. Specific meter types, pipe arrangements, and flow conditions can justify shorter or longer runs. Standards like ISO 5167 and ASME MFC-3M define exact requirements for each meter class.
Flow Meter Type Comparison
| Meter Type | Upstream (D) | Downstream (D) | Notes |
|---|---|---|---|
| Orifice Plate | 10–15 | 5 | Varies by beta ratio; narrower beta requires longer upstream |
| Venturi Tube | 5 | 3–5 | Self-recovering design; less sensitive to inlet conditions |
| Magnetic | 5–10 | 3–5 | Accepts shorter runs than DP meters; insensitive to velocity profile |
| Vortex | 10–20 | 5 | Sensitive to swirl; often needs more upstream than orifice |
| Ultrasonic (transit-time) | 10–15 | 5 | Highly affected by velocity asymmetry; demands clean approach |
| Turbine | 10–15 | 5 | Sensitive to swirl and yaw; long upstream reduces uncertainty |
| Coriolis (mass flow) | 0–5 | 0–5 | No straight pipe requirement; measures mass directly |
| Positive Displacement | 0–5 | 0–5 | No straight pipe requirement; output independent of profile |
Requirements by Meter Type
Orifice Plate Meters
Orifice plates are sensitive to inlet velocity profile. Beta ratio (ratio of orifice diameter to pipe diameter) directly affects requirements. At beta = 0.5, you may need 15D upstream. At beta = 0.7, 10D often suffices. The beta ratio changes the pressure drop and flow coefficient, which means the flow disturbance upstream has more or less impact on accuracy.
Field installations with two elbows in the same plane (90° apart) upstream of an orifice meter will show 2–4% higher discharge coefficient than the same meter with 15D straight pipe. This is why standards require either adequate straight run or flow conditioning devices.
Magnetic Flow Meters
Magnetic meters measure the voltage induced by fluid crossing perpendicular electrodes. This measurement is largely immune to velocity profile shape. You can often install one with 5D upstream and 3D downstream, even after an elbow, without significant accuracy loss.
The exception is extreme swirl. If the flow is rotating as it enters the meter, the voltage pattern shifts. This occurs when elbows are stacked perpendicular to each other (one horizontal, one vertical). Even then, 5D straight pipe usually corrects it.
Clogging concerns are the primary reason to maintain minimum straight pipe on magnetic meters—not to stabilize the velocity profile, but to allow solids to remain suspended in the center of the pipe rather than settling near electrodes.
Vortex Flow Meters
Vortex meters measure frequency of fluid oscillations downstream of a bluff body. Swirl entering the meter causes the shedding frequency to shift unpredictably, reducing accuracy. This makes vortex meters more demanding than orifice plates in terms of upstream requirements.
A common mistake is assuming vortex and orifice requirements are the same. Field data shows vortex meters need 15–20D upstream to tolerate two perpendicular elbows. With one elbow and 10D straight pipe, accuracy suffers noticeably in some flow conditions.
Ultrasonic Flow Meters (Transit-Time)
These meters calculate flow by measuring signal propagation time in two diagonal paths through the pipe. Velocity asymmetry—faster flow on one side—causes measurement error. Fully developed, symmetric flow is essential for accuracy above ±2% uncertainty.
Installation guidelines typically specify 10–15D upstream and 5D downstream. After a single elbow, the flow remains asymmetric well past 10D, so if you’re installing after an elbow, consider 20D of straight pipe or a flow straightener.
Turbine Flow Meters
Turbine meters are mechanically simple but sensitive to yaw (flow angle) and swirl. The rotor responds differently depending on the axial component versus the tangential component of velocity. This sensitivity demands good inlet conditions.
Most turbine installations need 10D upstream minimum. Some manufacturers specify 15D after elbows. Downstream, 5D is typical, though backpressure constraints (such as high-pressure applications) sometimes allow as little as 2D.
Coriolis and Positive Displacement Meters
These meters require no straight pipe for accuracy because they measure mass flow or volumetric displacement directly, independent of velocity profile. You can mount them immediately after an elbow with zero impact on measurement accuracy.
Coriolis meters do require some downstream space—not for the meter itself, but for pressure recovery. After the U-tube vibration channels, the flow expands back into the pipe. Allowing 2–5D downstream improves system stability and reduces noise in the signal.
Flow Conditioners and Alternatives
When you can’t meet straight pipe requirements, flow conditioners reduce the needed upstream length from 10D to as little as 2–3D. Common types include tube bundle straighteners, perforated plates, and honeycomb elements.
A tube bundle straightener (arrays of small tubes parallel to flow) costs €300–800 and works reliably. It recovers ~1D of pressure downstream, meaning your permanent pressure drop stays low. This is the best option in tight spaces.
Perforated plate straighteners are cheaper (€100–300) but cause higher permanent pressure loss. They’re adequate for low-speed applications or when small-scale mixing won’t hurt your measurement.
Never use a conditioner as a substitute for good upstream design if you can build the pipe properly. Straighteners add cost, maintenance, and pressure drop. Build 10D upstream when the space exists.
Common Installation Mistakes
Mistake 1: Assuming 10D is sufficient after any disturbance. It isn’t. A single elbow needs 10D, but two elbows (especially perpendicular elbows) need 15–20D for vortex or ultrasonic meters.
Mistake 2: Installing the meter too close to a tee junction. Tee junctions create complex flow patterns that persist for 20–30D. Always measure straight pipe distance from the meter, not from the tee itself.
Mistake 3: Neglecting downstream requirements. A 5D downstream run is just as important as upstream. Many sites focus only on upstream, then install a valve 2D downstream, invalidating both the upstream investment and the meter’s accuracy.
Mistake 4: Applying differential pressure meter rules to ultrasonic or turbine meters. Ultrasonic and turbine meters are more demanding. Don’t assume DP meter guidelines work for other types.
Mistake 5: Installing a flow conditioner, then positioning the meter immediately after it. Conditioners smooth the profile over a distance, not instantly. Leave 2D between the conditioner outlet and the meter.
Frequently Asked Questions
Can I measure pipe ID if the drawing is unavailable?
Yes. For a nominal 2-inch pipe, measure the outer diameter with calipers, then subtract twice the wall thickness (typically 0.154 inch for Schedule 40 steel). Or use a pipe measurement table. Once you have ID, multiply by 10 or 5 to get your required straight lengths.
What if I have only 8D upstream?
Your uncertainty increases, typically by 1–3% depending on meter type and what’s upstream. If the disturbance is a single elbow, an electromagnetic meter or Coriolis meter will work fine. For orifice plates or vortex meters, add a flow straightener.
Does reducer or enlarger fitting count toward straight pipe?
No. Reducers and enlargers create disturbances. Count straight pipe from the last fitting (elbow, tee, valve) to the meter inlet, or from the meter outlet to the next fitting downstream.
Is horizontal vs. vertical installation different?
Gravity affects settling of solids and gas bubbles, but doesn’t change the upstream/downstream rule. What changes is your risk of plugging or air entrainment. Vertical runs require attention to solids settling (magnetic meters) and gas pockets (ultrasonic meters), but straight pipe requirements remain the same.
Can I use the outlet of a storage tank as my upstream run?
Not reliably. Tank outlets create vortex, turbulence, and often asymmetric flow. Always install 10D of straight pipe after the tank discharge, treating the tank outlet as a disturbance source equivalent to an elbow or tee.
How do I select between a ultrasonic and turbine meter when space is limited?
Both need similar straight pipe lengths. If space is truly tight, consider magnetic or Coriolis meters, which tolerate shorter runs. See our flow meter type guide for detailed comparisons.
Featured Flow Meters from Sino-Inst
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Need help selecting the right flow meter for your application? Our engineering team can assist with sizing, installation guidance, and specifications tailored to your requirements.
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Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.
SMART HART Pressure Transmitter
What is a HART Pressure Transmitter?
The HART Pressure Transmitter is a two-wire intelligent pressure measurement instrument based on the HART protocol, suitable for precision fluid pressure measurement. The intelligent HART Pressure Transmitter retains a 4~20mA current loop signal while transmitting digital signals. Using a HART handheld device or a smart instrument with HART functionality, users can communicate with the pressure transmitter to perform parameter settings, read diagnostic information, and other operations.
Sino-Inst offers a variety of HART pressure transmitters for industrial pressure measurement. If you have any questions, please contact our sales engineers.
What is hART in a pressure transmitter?
The HART protocol is a backward-compatible smart instrument solution for the transition from analog to digital systems.
A typical HART smart instrument generally consists of a power supply module, sensor interface circuitry, A/D conversion circuitry, MCU, D/A output circuitry, and HART communication circuitry.
HART (Highway Addressable Remote Transducer) is a communication protocol introduced by Rosemount Corporation in 1985 for communication between field smart instruments and control room equipment.
Traditional pressure transmitters only provide a 4-20mA current loop output analog signal. HART smart pressure transmitters retain the 4-20mA current loop signal while transmitting digital signals, playing a crucial role in the transition from analog to digital instruments.
The HART protocol uses FSK frequency shift keying signals based on the Bell202 standard, superimposing a 0.5mA audio digital signal onto a low-frequency 4-20mA analog signal for bidirectional digital communication, with a data transmission rate of 1.2kbps. Since the average value of the FSK signal is 0, it does not affect the magnitude of the analog signal transmitted to the control system, ensuring compatibility with existing analog systems.
In HART protocol communication, the main variables and control information are transmitted via 4-20mA. Additional measurement, process parameters, equipment configuration, calibration, and diagnostic information can be accessed via the HART protocol when needed.
Benefits of HART pressure transmitters
- 4～20mA DC current output superimposed HART® protocol digital communication (two-wire system);
- Adopt digital compensation and nonlinear correction technology;
- -10℃～80℃ digital wide temperature compensation;
- With local and remote zero and span adjustment functions;
- Key operation on site for easy configuration.
- Shorten troubleshooting time from discovery to problem solving;
- Continuously verify the integrity of loops and control/automation system strategies;
- Improve asset efficiency and system availability;
- Quickly determine and verify control loops and device configurations;
- Use remote diagnosis to reduce unnecessary on-site inspections.
Featured Industrial HART Pressure Transmitters
HART pressure transmitter is a complete product line of liquid level, differential pressure, gauge pressure and absolute pressure transmitters. Models include flushing diaphragms and sanitary flanges for liquid level measurement, hydrostatic tank metering – HTG. And wetted parts of various materials to suit the process requirements.
HART calibrator is our HART communicator for calibrating instruments. For example pressure transmitter, DP transmitter, liquid level transmitter, a flowmeter, and a temperature transmitter.
HART communication protocol (Highway Addressable Remote Transducer) is a hybrid analog + digital industrial automation open protocol. Its most significant advantage is that it can communicate through the traditional 4–20 mA analog instrument current loop, sharing only a pair of wires used by the analog host system.
We use this protocol in the HART calibrator. HART communicator (such as HART 475) is the most common HART calibrator.
The proprietary calibration process ensures optimal temperature compensation. This limits the thermal impact on the sensor output. It is suitable for the global process control industry. It provides a cost-effective solution for the use of conventional HART transmitters (such as the HART 475 field communicator).
No. HART is different from 4-20mA. Their main differences are:
- Signal Type
4-20mA: Pure analog signal, transmitting only a single process variable (e.g., pressure, flow rate) via current value (4mA-20mA), unable to carry additional data.
HART Protocol: Superimposes a digital signal (FSK modulation) onto the 4-20mA analog signal, enabling dual-channel analog and digital communication, capable of transmitting multiple parameters such as equipment status and diagnostic information.
- Communication Capabilities
4-20mA: Unidirectional transmission, supporting only basic measurements, unable to be remotely configured or diagnosed.
HART Protocol: Half-duplex bidirectional communication, supporting remote parameter modification (e.g., range, zero point) and fault diagnosis (e.g., sensor malfunction, loop impedance exceeding limits).
- System Compatibility
4-20mA: Requires physical disconnection of the loop for maintenance, cannot be networked with intelligent devices.
HART Protocol: Compatible with traditional analog systems, supports a single-line connection of up to 15 devices, and can be upgraded to WirelessHART or HART IP in the future.
- Applications
4-20mA: Suitable for simple applications with limited budgets and only basic measurements required.
HART Protocol: Suitable for high-precision control, smart factories, and other scenarios requiring data interaction, with lower long-term maintenance costs.
The HART protocol extends the functionality of 4-20mA through digital signals, enabling intelligent upgrades, while traditional 4-20mA only retains basic analog transmission capabilities.
You may like: Verabar Flow Meter
How to calibrate a pressure transmitter using HART?
A pressure transmitter is one of the most common instruments in a process plant. To assure its accuracy, it needs to be calibrated.
But what do you need to calibrate it and how is it done?
You may know how to calibrate a pressure transmitter? Or, how to calibrate a differential pressure transmitter? Then, calibrate HART pressure transmitters, kind of like pressure transmitter calibration using a hart communicator. Pressure transmitter manufacturers have improved accuracy and technology, designed into these smart pressure measurement devices.
To calibrate a pressure transmitter, you need:
loop supply (if not connected to the controls system’s loop supply);
a pressure generator to generate input pressure;
an accurate calibrator to measure the input pressure;
an accurate calibrator to measure the output mA current.
Typically, the pressure transmitter is a HART protocol transmitter. So in case, there is any need to adjust/trim it, you will need to use a device supporting HART communication.
How to calibrate HART pressure transmitters?
Explaining how to do the calibration would result in quite a long text. So we have put together a video for you instead. The video shows you how to calibrate and trim a HART pressure transmitter. Please have a look at the video: How to calibrate HART pressure transmitters
Video source: https://www.youtube.com/watch?v=4wLCqH0M9fU&t=9s
HART Pressure Transmitters Calibration Steps
How to calibrate HART pressure transmitters?
Total Time: 20 minutes
1. Isolate the transmitter from the process being measured and its loop wiring.
2. If measuring the mA signal across the transmitter test diode leave the wires intact, but note this method does not give the best mA measurement accuracy.
3. Connect the mA measurement jacks of the 754 to the transmitter.
4. Connect the pressure module cable to the 475, and connect the transmitter test hose from the hand pump to the transmitter.
Press the HART button on the calibrator to see the configuration of the transmitter.
5. Press HART again and the calibrator will offer the correct measure/source combination for the test.
6. If documenting the calibration press As-Found, input the test tolerance and follow the prompts.
7. If the measured mA signal at the test points is found within tolerance the test is complete.
If not, change is required.
Select, adjust, and trim the pressure zero, mA output signal and input sensor.
If you still do not know how to check the pressure transmitter? Or, how to calibrate a pressure transmitter. Just contact us.
More Pressure Measurement Solutions
- High Frequency Dynamic Pressure Sensor
- Intrinsically Safe vs Explosion Proof Pressure Transmitters
- How to Calibrate a Pressure Transmitter
- Differential Pressure Transmitter Installation Guide
- Use Differential Pressure Transmitter to Measure Liquid Level
- MEMS Pressure Sensors
- Application Analysis of Intelligent Pressure Transmitter
- Differential Pressure Flow Meters
- Water Pressure Transducers
- Capacitive pressure transducer
- Pressure indicator transmitters
- How Does a Pressure Transmitter Work?
- Pressure Transmitter Calibration
Sino-Inst offers over 20 SMART HART Pressure Transmitters. About 50% of these are 4-20ma Low-Pressure Transducers, 40% are Differential Pressure Gauge, and 20% are Diaphragm Seal Pressure transmitters, 20% are 4-20ma differential pressure transmitters.
Sino-Inst sells through a mature distribution network that reaches all 50 states and 30 countries worldwide. HART Pressure Transmitter products are most popular in the domestic market, Southeast Asia, and Mid East. You can ensure product safety by selecting from certified suppliers with ISO9001, ISO14001 certifications.
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Please enable JavaScript in your browser to submit the form
Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.
Diaphragm Seal Pressure Transmitter － Flush Flanged
The flush flanged diaphragm seal pressure transmitter uses a diaphragm directly welded to the mounting flange, working in conjunction with an inline pressure transmitter to protect against the effects of high and low temperatures, corrosive, clogging, or erosive processes.
Sino-Inst offers a variety of Diaphragm Seal DP/Pressure Transmitters for industrial pressure measurement. If you have any questions, please contact our sales engineers.
Features of Diaphragm Seal Pressure Transmitter
- Flange installation; flange size and standards can be customized.
- Diaphragm isolation technology.
- Two-wire system, 4-20mA analog output, HART protocol digital communication.
- Intelligent LCD display with backlight.
- Large diaphragm, fully welded seal, long-term reliability and durability.
- Corrosion-resistant diaphragm options available (tantalum, HaC, 316L, 316L PTFE sprayed).
- Especially suitable for high-temperature viscous liquids.
- HART communication function available.
Read more about Steam pressure transmitter-Pressure measure on steam pipeline
Specifications of Diaphragm Seal Pressure Transmitter
| Measuring medium: | Liquid or gas (compatible with contact material) |
| Pressure range: | -100kPa～0～10MPa (see range selection table for details) |
| Pressure method: | Gas pressure, absolute pressure |
| Medium temperature: | -40～130℃, other high temperatures can be customized up to 60℃ |
| Connection time: | 20ms |
| Accuracy class: | ±0.5%FS |
| Indicator accuracy: | 0.05%FS LCD (with backlight) display |
| Temperature compensation: | -20～80℃ |
| Stability performance: | ±0.2%FS/year |
| Temperature drift: | ±0.02%FS/℃ (within temperature compensation range) |
| Explosion-proof type: | Explosion-proof type ExdbⅡCT6Gb; Explosion-proof dust type ExtbIIICT80℃Db; Intrinsically safe type ExiaⅡCT6Ga (4～20mA/4～20mA HART output only); Dust intrinsically safe type ExiaD20T80℃ (4～20mA/4～20mA HART output only); |
| Protection class: | IP66; |
Applications
The Flush Flanged Diaphragm Seal Pressure Transmitter uses a standard flange as its interface, allowing for on-site flange installation. Because the pressure-bearing diaphragm is exposed and directly senses the pressure, it is easy to clean and meets harsh operating conditions such as moisture resistance, waterproofing, and explosion protection.
This series of products is widely used in industrial process control, petroleum, chemical, and metallurgical industries, as well as in applications involving viscous media containing particles.
- High/low temperature fluids;
- Highly corrosive/high viscosity fluids;
- The fluids which may cause clogging of impulse piping in the low temperature;
- Toxic fluids;
- The fluids containing suspended solids which are deposited in the impulse piping and may cause clogging.
Extended reading: Featured Diaphragm Seal Pressure Transmitters
Diaphragm flange material selection
The biggest advantage of the Diaphragm Seal Pressure Transmitter is the availability of various diaphragm materials. Commonly used diaphragm materials include SUS316L stainless steel, tantalum, Hastelloy, Monel alloy, pure titanium, and F4 alloy.
Choosing the right material means considering both its corrosion resistance and cost-effectiveness. For example, tantalum and Hastelloy diaphragms offer excellent corrosion resistance but are expensive, making them suitable only for highly corrosive environments; other inexpensive materials are not suitable.
The table below introduces several commonly used corrosion-resistant materials suitable for corrosive media for your reference.
| Corrosive medium | Tin bronze (QSn6.5-0.4) | SUS316 | Pure tantalum (Ta) | Monel (Ni70Cu30) | Hastelloy (HC) | Polytetrafluoroethylene (F4) |
| Sulfuric acid (H2SO4) | V | △ | ○ | V | V | V |
| Nitric acid (HNO3) | ╳ | V | ○ | ╳ | V | V |
| Hydrochloric acid (HCI) | △ | ╳ | ○ | ╳ | V | V |
| Phosphoric acid (H3PO4) | V | V | ○ | V | V | V |
| Acetic acid (CH3COOH) | V | V | ○ | V | ○ | V |
| Caustic soda (NaOH) | △ | ○ | △ | ○ | ○ | V |
| Soda ash (Na2CO3) | ○ | ○ | ○ | ○ | V | V |
| Baking soda (NaHCO3) | V | ○ | ○ | ○ | ○ | V |
| Chlorine (CI) | Dry: V | Dry: V | ○ | Dry: V | V | V |
| Wet: ╳ | Wet: ╳ | Wet: ╳ | ||||
| Bromine (Br2) | Dry: △ | Dry: ╳ | ○ | Dry: ○ | ○ | V |
| Wet: ╳ | Wet: △ | Wet: ╳ | ||||
| Ammonia (NH3) | ╳ | V | ╳ | ╳ | ○ | V |
| Seawater (30% NaCI) | V | V | ○ | ○ | ○ | V |
Extended reading: Common Pressure Sensor Applications
What is a diaphragm seal pressure transmitter?
The diaphragm seal pressure transmitter is a flange-type pressure transmitter. This type of pressure transmitter assembles diaphragm seals to field transmitters for the purpose of measuring pressure, pressure or level.
What is a diaphragm seal?
Diaphragm Seals, also known as Chemical Seals or Gauge Isolators, are used to isolate pressure instrumentation, like pressure gauges, pressure transmitters, pressure switches, level transmitters, and more, from process media that is hot, corrosive, clogging, or otherwise damaging to the pressure instrument.
A diaphragm seal has two primary tasks:
- Separation of the measuring instrument from the process medium
- Transfer of the pressure to the measuring instrument
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What is a remote seal?
The remote seal is used to prevent the medium in the pipeline from directly entering the pressure sensor assembly in the pressure transmitter. It is connected to the transmitter by a capillary filled with fluid. As a result, they’re often used in refining, petrochemical, and chemical plants.
Extended reading: SI-703 Flush Diaphragm Pressure Sensor
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FAQ
Sino-Inst is Flush Flanged Diaphragm Seal Pressure Transmitters manufacturer in China. We offer all types of Pressure Level Transmitters. Like Direct Mounted, flange-mounted, single flange, double flange, Remote Diaphragm Seals, High Static, Digital Remote.
Most of our Diaphragm Seal Pressure Transmitters are used in oil, liquids, DP transmitters, flow measurement, level measurement (like the ultrasonic level measurement), density, and other process variables.
You can ensure product safety by selecting from a certified supplier with ISO9001, ISO14001 certification. We will share more about instrument calibration, like the flow transmitter calibration.
Request a Quote
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Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.
Flange Mounted Differential Pressure Transmitter
The Flange Mounted Differential Pressure Transmitter is based on an intelligent differential pressure transmitter and features a flush-mounted or extended flange. It is suitable for measuring the level, differential pressure, and density of liquids that are prone to crystallization or sedimentation. Equivalent to model EJA210E.
Can be directly installed on tanks or pipelines. It is used for measuring high-temperature, easily solidifying or crystallizing, suspended solids-containing, highly viscous, highly corrosive, or other media that require hygienic conditions and cannot be contaminated.
Sino-Inst offers a variety of flange-mounted DP transmitters for industrial pressure measurement. If you have any questions, please contact our sales engineers.
Sino-Inst Flange Mounted Differential Pressure Transmitter uses advanced microprocessing technology and digital communication technology. It outputs a 4~20 mA DC signal corresponding to the measured differential pressure. It can also be configured with the HART protocol.
Flange Mounted Differential Pressure Transmitter Features:
Extended reading: Smart Differential Pressure Transmitter
Specification of Flange Mounted Differential Pressure Transmitter
| Model | Transmitter type | |||
| SMT3151LT | Flange Mounted Differential Pressure Transmitter | |||
| Code | Scale range | |||
| 4 | 0-4.0～40kPa(0-400～4000mmH2O) | |||
| 5 | 0-20～200kPa(0-2～20mH2O) | |||
| 6 | 0-70～700kPa(0-7～70mH2O) | |||
| 7 | 0-210～2100kPa(0-21～mH2O) | |||
| Code | Output form | |||
| E | Linear output 4-20mAdc | |||
| SF | Linear output 4-20mAdc +HART signal | |||
| F | MODBUS-485 signal | |||
| Code | Flange standard (high pressure side flange) | |||
| A | ANSI American Standard (HG20615) | |||
| D | DIN European Standard (HG20592) | |||
| Code | Process connection size | |||
| ANSI American Standard (HG20615) | DIN European Standard (HG20592) | |||
| 25 | 1” | DN25 | ||
| 40 | 1.5” | DN40 | ||
| 50 | 2” | DN50 | ||
| 80 | 3” | DN80 | ||
| 0 | 4” | DN100 | ||
| Code | Process connection pressure rating | |||
| ANSI American Standard (HG20615) | DIN European Standard (HG20592) | |||
| A | 150LB | PN16/25 | ||
| B | 300LB | PN40 | ||
| C | 600LB | PN64 | ||
| D | 900LB | PN100 | ||
| Code | High pressure side diaphragm | |||
| A | 316 stainless steel | |||
| B | Hastelloy C | |||
| C | Monel | |||
| D | Tantalum | |||
| E | Titanium | |||
| F | Special Requirements | |||
| Code | High pressure side insert tube length | High pressure side insert cylinder material | ||
| A | 0 mm | None | ||
| B | 50 mm | 316L Stainless steel | ||
| C | 150 mm | 316L Stainless steel | ||
| D | 200 mm | 316L Stainless steel | ||
| Code | High pressure side filling fluid | |||
| D | General silicone oil （-40~104℃） | |||
| F | High temperature silicone oil （-40~304℃） | |||
| S | Inert liquid （-40~204℃） | |||
| Low pressure side structural material | Flange (joint) | Exhaust/drain valve | Isolation diaphragm | Sensor filling fluid |
| 22 | 316 Stainless steel | 316 Stainless steel | 316 Stainless steel | Silicone oil |
| 23 | 316 Stainless steel | 316 Stainless steel | Hastelloy C | Silicone oil |
| 24 | 316 Stainless steel | 316 Stainless steel | Monel | Silicone oil |
| 25 | 316 Stainless steel | 316 Stainless steel | Tantalum | Silicone oil |
| 33 | Hastelloy C | Hastelloy C | Hastelloy C | Silicone oil |
| 35 | Hastelloy C | Hastelloy C | Tantalum | Silicone oil |
| 44 | Monel | Monel | Monel | Silicone oil |
| S2 | A remote transmission device (with a remote transmission device on the low-voltage side) | |||
| Code | Shell material | Conduit inlet dimensions | ||
| A | Low copper aluminum alloy polyurethane coating | M20×1.5 | ||
| B | Low copper aluminum alloy polyurethane coating | 1/2-14 NPT | ||
| C | Stainless steel | M20×1.5 | ||
| D | Stainless steel | 1/2-14 NPT | ||
| Code | Optional parts | |||
| M1 | 0～100% Linear indicator head | |||
| M4 | LCD multi – power digital display head | |||
| D1 | Side discharge valve at the top (only for the low pressure side of the low pressure side without remote transmission) | |||
| D2 | Side discharge valve at the top (only for the low pressure side of the low pressure side without remote transmission) | |||
| Da | Flameproof ExdIIBT5Gb;(explosion-proof certificate no. : CE16.1163) | |||
| Fa | Intrinsically safe ExiaIICT4 / T5 / T6Ga;(explosion-proof certificate no. : CE15.2354X) | |||
| CX | With corresponding 316 flushing ring |
Extended Reading:
Applications
The Flange Mounted Differential Pressure Transmitter can accurately measure the liquid level and density of various containers. There are two types of flat flange and insert flange. It is suitable for high-viscosity medium or suspended liquid measurement.
- Viscous medium at high temperature;
- Easily crystallized medium;
- Precipitation medium with solid particles or suspended matter;
- Strongly corrosive or highly toxic medium;
- It can eliminate the leakage of the pressure guiding pipe and pollute the surrounding environment. It can avoid the instability of the measurement signal when the isolation liquid is used. The tedious work of frequently supplementing the isolation liquid is required;
- Continuously and accurately measure the interface and density;
- The remote transmission device can avoid the mixing of different instantaneous media so that the measurement results truly reflect the actual situation of process changes;
- Places with high sanitation requirements;
- Such as in the production of food, beverage, and pharmaceutical industries. Not only the transmitter contacting the media parts meet hygienic standards, but also should be easy to wash. To prevent cross-contamination of different batches of media.
Pressure level transmitter is good for level measurement. Most of the time, we use submersible hydrostatic level sensor for the level measurement. When you can not use the probe of hydrostatic level sensor, you can try with this pressure level transmitter. Pressure level transmitter, is one type of DP level measure instrument, with the diaphragm.
The SMT3151LT differential pressure level transmitter is a new type of differential pressure transmitter manufactured using advanced technology and equipment. Equipped with dual remote seals, it can be used for continuous measurement of liquid level, flow rate, and differential pressure. It offers particular advantages in applications involving sealed storage tanks.
Flange Mounted Differential Pressure Transmitter Working principle
Differential pressure transmitters utilize the pressure difference generated by the liquid’s own gravity to measure the liquid level in a container.
Flange-mounted differential pressure transmitters are directly installed on pre-existing flanges at the bottom of pipes or containers, contacting the liquid through an isolation diaphragm.
When the diaphragm is subjected to pressure, it undergoes slight deformation. The displacement of the diaphragm changes with the differential pressure. This change is precisely converted by an amplification circuit into a 4-20mA DC two-wire current, voltage, or digital HART output signal, thus achieving pressure measurement and transmission.
The high-pressure side measuring tube is always filled with the medium, maintaining constant pressure. The low-pressure side measuring tube forms a communicating vessel with the container, and its pressure changes linearly with the liquid level in the container.
Let △P be the differential pressure signal received by the transmitter, P0 be the internal pressure of the container, P+ be the pressure on the positive pressure side of the transmitter, and P- be the pressure on the negative pressure side of the transmitter. Let ρ be the density of the liquid in the container, g be the acceleration due to gravity, h1 be the height from the process zero point to the upper pressure tap of the container, h2 be the process liquid level in the container, and h be the height from the transmitter to the process liquid level zero point.
Then:
P+ = P0 + ρgh1 + ρgh
P- = P0 + ρgh2 + ρgh
△P = P+ – P- = ρgh1 – ρgh2
When the liquid level changes from h2=0 to h2=h1, the differential pressure measured by the transmitter changes from its maximum value to △P=0. By configuring the transmitter, the output current changes from 4mA to 20mA.
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Single flange vs Double flanges differential pressure level transmitter
- In principle: all are differential pressure transmitters + flange guide pressure;
- In terms of structure: the single flange liquid zd position transmitter has only one flange diaphragm box connected to the high pressure side, and the low pressure side to the atmosphere. The double flange liquid level transmitter is high and low pressure side through oil-filled capillary It is connected with two flanged membrane return boxes. There is also a capillary. The single flange transmitter is installed below, and a capillary is drawn from the low pressure side of the single flange transmitter to the upper flange membrane box.
- In terms of engineering applications: all can only measure the liquid level of fixed density. The single-flange transmitter can only be used for the liquid level of atmospheric equipment that can be imagined with the atmosphere. The double-flange transmitter can be suitable. Answer: Use closed equipment kettle to measure liquid level;
- From the economical point of view, the double flange is definitely more expensive than the single flange. After all, there is one more flange capsule and capillary.
Piezoresistive Differential Pressure Transmitter utilizes the piezoresistive effect of semiconductor silicon materials. Realize accurate measurement of differential pressure.
Smart Differential Pressure Transmitter measures industrial differential pressure. Can Works with diaphragm seals, capillary, HART. Outputs standard signals (such as 4 ~ 20mA, 0 ~ 5V).
When the process medium should not come into contact with the pressured parts of the measuring instrument. Diaphragm sealed pressure transmitters are used for pressure measurement.
High-temperature pressure transmitters with a 4-20mA output.
which has a temperature capability of over 850 °C and is not pyroelectric.
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- Use Differential Pressure Transmitter to Measure Liquid Level
Sino-Inst is one of the most excellent DP transmitters, pressure transmitters, and level transmitters suppliers. Sino-Inst can offer you a complete solution for pressure transmitters.
Sino-Inst can offer you with Flange Mounted Differential Pressure Transmitters. Our transmitters can work for you just like EJA210E.
Our Flange Mounted Differential Pressure Transmitters are widely exported to various countries. Including USA, UK, Argentina, Singapore, etc. If you need to purchase Flange Mounted Differential Pressure Transmitter, or have related technical questions, please feel free to contact our sales engineers!
Request a Quote
Please enable JavaScript in your browser to submit the form
Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.
SMT3151DP Smart Differential Pressure Transmitter
The SMT3151DP Smart Differential Pressure Transmitter utilizes a single-crystal silicon sensor with German MEMS technology, offering higher measurement accuracy. It outputs standard signals (e.g., 4-20mA, 0-5V) and can also be configured with RS485 Modbus RTU or HART protocols.
The single-crystal silicon sensor core features a dual-beam suspension design, significantly improving accuracy and resistance to unilateral and bilateral overload. A built-in intelligent signal processing module achieves perfect integration of static pressure and temperature compensation. This enhances measurement accuracy and long-term stability across a wide range of static pressure and temperature variations.
Sino-Inst offers a variety of smart differential pressure sensors for industrial pressure measurement. If you have any questions, please contact our sales engineers.
Features
- Output signal 4-20mA output+RS485/HART communication;
- 0.075%FS high accuracy, millisecond-level ultra-fast response;
- Built-in three-button quick operation for on-site adjustment;
- Self-diagnosis capability;
- Range coverage is 0-0.1KPa~41.0MPa;
- Good stability, high precision, adjustable damping, strong resistance to one-way overload.
- Explosion-proof housing structure.
- LCD display;
- IP67 protection rating;
- Intelligent static pressure compensation and temperature compensation protect the transmitter from the effects of temperature, static pressure, and overpressure, controlling the overall measurement error at the site within the specified parameters;
- High static pressure resistance, up to 40MPa;
Extended reading: How to calibrate HART pressure transmitters
Technical Specifications
| Measurement Range | 1KPa, 4KPa, 40KPa, 100KPa, 400KPa, 4MPa, 40MPa |
| Single-Side Overpressure | 16MPa |
| Dual-Side Static Pressure | 16MPa 25MPa 40MPa |
| Measurement Accuracy | ±0.075%, ±0.1%, ±0.5% (including linearity, hysteresis, and repeatability from zero) |
| Measured Medium | Gas, Liquid, Steam |
| Output Signal | 4~20mA DC+RS485/HART protocol |
| Power Supply | General 10.5~45VDC, intrinsically safe explosion-proof 10.5-26VDC |
| Power Line Spacing | 15cm and above (avoid parallel wiring) |
| Saturation Current | Upper limit 20.8mA, lower limit 3.8mA |
| Alarm Current | Upper limit 22.8mA, lower limit 3.6mA (mode adjustable) |
| Adjustment Function | Zero and full-scale points can be adjusted locally via the three buttons on the top of the casing or remotely via configuration software |
| Zero Shift | Can be shifted within the range of -20% to +20% of the maximum range |
| Output Method | Linear output Square root output (can be remotely adjusted via configuration software) |
| Operating Temperature | -40~85℃ |
| Measured Medium Temperature: | -40℃~120℃ (High temperature customizable) |
| Diaphragm Material | 316L stainless steel/Hastelloy alloy/Tantalum diaphragm/Gold-plated diaphragm |
| Position Effect | Approximately 200Pa between horizontal and vertical positions |
| Response Time | 10ms |
| Static Pressure Effect | < 0.05%FS/10MPa |
| Overpressure Effect | < 0.05%FS/10MPa |
| Stability | ≤0.03%FS/year |
| Power Supply Effect | < 0.005%FS/V |
| Explosion-Proof Rating: | Exd Ⅱ CT6 Gb, Exia Ⅱ CT6 Ga |
| Enclosure Protection Rating: | IP67 |
SMART Differential Pressure Transmitter Datasheet
Order Guide
Use object: liquid, gas, or steam
| Model | Transmitter type |
| DP | Pressure transmitter |
| HP | Absolute pressure transmitter |
| Code | Scale range |
| 2 | 0-0.10～3.5kPa(0-10～350mmH2O) |
| 3 | 0-0.8～8.0kPa(0-80～800mmH2O) |
| 4 | 0-4.0～40kPa(0-400～4000mmH2O) |
| 5 | 0-20～200kPa(0-2000～20000mmH2O) |
| 6 | 0-70～700kPa(0-0.7～7kgf/cm2) |
| 7 | 0-210～2100kPa(0-2.1～21kgf/cm2) |
| 8 | 0-700～7000kPa(0-7.0～70kgf/cm2) |
| 9 | 0-2.1～21MPa(0-21～210kgf/cm2) |
| 0 | 0-4.1～41MPa(0-41～4100kgf/cm2) |
| Code | Output form |
| E | Linear output 4-20mAdc |
| SF | Linear/square root output 4-20mAdc +HART signal,，Full function buttons on site |
| F | MODBUS-485 signal |
| Structural materials | Flange connector | Exhaust/Drain valve | Isolation diaphragm | Filling liquid |
| 22 | 316 Stainless steel | 316 Stainless steel | 316 Stainless steel | Silicone oil |
| 23 | 316 Stainless steel | 316 Stainless steel | Hastelloy C | Silicone oil |
| 24 | 316 Stainless steel | 316 Stainless steel | Monel | Silicone oil |
| 25 | 316 Stainless steel | 316 Stainless steel | Tantalum | Silicone oil |
| 33 | Hastelloy C | Hastelloy C | Hastelloy C | Silicone oil |
| 35 | Hastelloy C | Hastelloy C | Tantalum | Silicone oil |
| 44 | Monel | Monel | Monel | Silicone oil |
| Code | Shell material | Conduit inlet dimensions | ||
| A | Low copper aluminum alloy polyurethane coating | M20×1.5 | ||
| B | Low copper aluminum alloy polyurethane coating | 1/2-14 NPT | ||
| C | Stainless steel | M20×1.5 | ||
| D | Stainless steel | 1/2-14 NPT |
| Code | Pressure connection | |
| L1 | 1/4NPT-18 Internal thread（excluding waist joint standard） | |
| L2 | 1/2NPT-14 Internal thread | |
| L3 | M20×1.5 External thread | |
| Code | Optional parts | |
| M4 | LCD multi – power digital display head | |
| B1 | Pipe bending bracket | |
| B2 | Plate bending bracket | |
| B3 | Pipe mounting bracket | |
| C02 | M20×1.5 nut and Φ 14 pressure short tube | |
| C12 | 1/2NPT-14 external thread and Φ14 pressure short tube | |
| C22 | 1/4NPT-18 external thread and Φ14 pressure short tube | |
| C32 | 1/4NPT-18 to M20×1.5 external thread | |
| C42 | 1/2NPT-14 to M20×1.5 external thread | |
| C43 | 1/2NPT-14 to 1/4NPT-18 internal thread | |
| C44 | 1/2NPT-14 to 1/2NPT-14 external thread | |
| C45 | 1/2NPT-14 to G1/2 external thread | |
| D1 | The side discharge valve is on the upper part | |
| D2 | The side discharge valve is on the upper part | |
| X1 | Oil ban | |
| Da | Flameproof ExdIIBT5Gb;(explosion-proof certificate no. : CE16.1163) | |
| Fa | Intrinsically safe ExiaIICT4/T5/T6Ga;(explosion-proof certificate no. : CE15.2354X) |
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Working principle of SMART differential pressure transmitter
The intelligent differential pressure transmitter uses a single-crystal silicon piezoresistive sensor as its core component. When pressure is applied to the sensor, the resistance of the single-crystal silicon changes, which is converted into an electrical signal by the circuit, and then digitally processed to output a standard signal (such as 4-20mA or a digital signal).
Its intelligent feature lies in its built-in microprocessor, which can perform temperature compensation, linear correction, and fault diagnosis, ensuring high measurement accuracy and stability.
The SMT3151DP intelligent differential pressure transmitter integrates differential pressure measurement, display, and signal output functions. This intelligent differential pressure transmitter is used to measure the level, density, flow rate, and pressure of liquids, gases, or vapors.
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Smart Differential Pressure Transmitter Applications
SMT3151DP smart differential pressure transmitter is suitable for applications like:
- Flow measurement;
- The differential pressure transmitter is combined with the throttling device (like the orifice plate). To convert the flow rate according to the differential pressure value, generated before and after the throttling device.
- Level monitoring;
- Measuring the height of the liquid by the pressure difference, generated by the gravity of the liquid itself.
- Steam measurement;
- Filter or pump differential pressure;
- For Monitoring Hydronic HVAC Systems.
- Critical process monitoring.
Generally used in liquid, gas or steam differential pressure, flow measurement. The medium temperature is not too high, corrosion is not strong, viscosity is not high, not easy to crystallize and other environments.
If the working static pressure exceeds 16MPa, a high static differential pressure transmitter should be selected.
FAQ
More Featured Pressure Measurement Solutions
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- Different Types of Pressure: Absolute, Gauge, Sealed Gauge and Differential Pressure
Sino-Inst is a leading manufacturer in the field of measurement and control in China. One big reason for the continued growth of Sino-Inst is our willingness to listen to our customers’ specific needs.
Sino-Inst manufactures a wide variety of mechanical and electronic devices. To measure pressure, level measurement, temperature, and flow. And we’re working constantly to improve our product platform.
If you need to purchase Smart Differential Pressure Transmitters or have related technical questions, please feel free to contact our sales engineers!
Request a Quote
Please enable JavaScript in your browser to submit the form
Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.
DP Level Transmitter for Tank Level Measurement
The DP level transmitter works on the principle that the hydrostatic pressure difference of a liquid is directly proportional to the liquid level height. It calculates the liquid level by measuring the pressure difference of the medium inside the container and outputs a standard electrical signal. The dual-flange capillary structure provides mechanical and thermal isolation, allowing it to handle complex corrosive and high-temperature media in various industrial processes and tank level monitoring applications.
Sino-Inst offers a variety of DP Level Transmitters for industrial pressure measurement. Connection with diaphragm seals. If you have any questions, please contact our sales engineers.
Features
Specifications of DP level transmitter
| Measuring Medium: | Gases, Vapors, Liquids |
| Measuring Range | -100kPa…0~6kPa…7MPa |
| Accuracy: | ±0.075%, ±0.1%, ±0.2% (including linearity, hysteresis, and repeatability from zero point) |
| Stability: | ±0.2%/year |
| Power Supply: | 10–36V DC (24V DC recommended) |
| Reference Accuracy for Range Adjustment: | If TD > 10 (TD = Maximum range / Adjustable range), then: ±(0.075 × TD)% |
| Ambient Temperature: | -40℃ ~ 85℃ |
| Measuring Medium Temperature: | -40℃ ~ 400℃ (higher/lower temperatures can be customized) |
| Storage Temperature: | -40℃ ~ 85℃ |
| Display: | LCD, OLED |
| Display Module Temperature: | -20℃ ~ 70℃ (LCD), -40℃ ~ 80℃ (OLED) |
| Measuring Diaphragm: | 316L, Hastelloy C, Tantalum, Titanium, Nickel, Monel, Duplex Stainless Steel, PFA, Gold Plating |
| Process Connection: | Stainless steel 316L, 304 |
| Filling Fluid: | Silicone oil, fluorinated oil, etc. |
| Transmitter Housing: | Aluminum alloy material, epoxy resin coating on the surface |
| Housing Seal: | Nitrile rubber |
| Nameplate: | Stainless steel 304 |
| Enclosure Protection Rating: | IP67 |
| Explosion Protection Rating: | Exd Ⅱ CT6 Gb, Exia Ⅱ CT6 Ga |
| Measuring Range Limits | Within the upper and lower limits of the range, it can be set arbitrarily, as long as the calibrated range ≥ the set range. It is recommended to choose a range with the lowest possible range ratio to optimize performance. |
| Influence of Mounting Position | Changes in installation position will cause zero point influence, which can be corrected by zero adjustment; there is no range influence. |
| Output | Two-wire 4-20mA, compliant with NAMUR NE43 standard, superimposed digital signal (Hart protocol) |
| Output Signal Limits | Imin (minimum): 3.9mA Imax (maximum) = 21.0mA |
| Alarm Current | Low alarm mode (minimum): 3.9mA High alarm mode (maximum): 21mA (user pre-settable) |
| Default Alarm Current Setting | High alarm mode |
| Fault Warning | If the sensor or circuit fails, the automatic diagnostic function automatically outputs 22.0mA |
| Response Time | Amplifier component damping constant is 0.1s; sensor time constant is 0.1–1.6s, depending on the range and range ratio. Additional adjustable time constant: 0–100s |
| Warm-up Time | <15s |
There are 5 types of remote transmission devices for remote differential pressure transmitters:
- Flat type
- Thread mounting type
- Flange mounting type
- Extended Diaphragm Seal
- Wet legs/Dry legs
Applications of DP level transmitters
The differential pressure liquid level transmitter can prevent the measured medium from directly contacting the sensor diaphragm of the transmitter. It is suitable for the following situations:
- When the measured medium has a corrosive effect on the transmitter connector and sensitive components;
- When the high temperature measured medium needs to be isolated from the transmitter;
- When there are solid suspended solids or high viscosity in the measured medium, it is easy to block the transmitter connector and the pressure chamber;
- When the measured medium is easily cured or crystallized by the pressure tube;
- When changing the measured medium needs to be rinsed and not to be mixed;
- Hygienic conditions must be maintained to prevent pollution. .
- Changing the measured medium requires strict purification of the measuring head
- Suspended liquid or high viscosity medium
- Measurement of sealed pressure vessel.
Read more What is a diaphragm seal?
DP level transmitter working principle
The differential pressure level transmitter is an instrument that uses the pressure generated by the liquid column to measure the height of the liquid level. When the liquid level changes, the pressure received by the diaphragm at the high-pressure side flange will change accordingly. The differential pressure value calculated by the transmitter will also change accordingly. There is a linear relationship between them.
Normally, the high-pressure side (H side) and the low-pressure side (L side) cannot be installed reversely. Generally, the H side is installed at the lower part of the equipment, and the L side is installed at the higher part of the equipment. Before installation, the flange surface of the equipment should be cleaned and the gasket should not be placed off-center to prevent the diaphragm from being punctured or deformed, causing distortion of the transmitter.
Differential pressure transmitter level measurement calculation
When using a Differential pressure (DP) level transmitter to measure the liquid level as shown in the figure below.
The measured liquid density in the figure is ρ.
The working medium density in the capillary of the double flange differential pressure transmitter is ρ0.
The measuring range of the measured liquid level is H.
The center distance of the sampling tube of the measured liquid level is h.
It can be seen from the figure that the maximum measurement range of the liquid level △ P = P + — P- = H × ρ × g – h × ρ0 × g.
It can be seen from the formula that the dual-flange differential pressure transmitter should perform negative migration. The migration amount S is h × ρ0 × g. And the installation position of the double flange differential pressure transmitter has no effect on the migration amount and the measurement result.
The dual-flange differential pressure transmitter requires negative migration.
When the measured liquid level is 0, the pressure difference between the positive and negative measurement chambers of the remote differential pressure transmitter is the largest. The output current of the double flange differential pressure transmitter is 4mA.
As the measured liquid level rises, the pressure difference between the positive and negative measurement chambers of the transmitter gradually decreases.
When the measured liquid level rises to the highest Hmax. The pressure difference between the positive and negative measurement chambers of the transmitter is the smallest. The output current of the double flange differential pressure transmitter is 20mA.
Read more about: Differential Pressure Transmitter Installation Guide
DP level transmitter calibration
The differential pressure liquid level transmitter has been calibrated in the range, accuracy, linearity and other parameters according to customer requirements at the factory. And mark the range, accuracy, etc. on the nameplate of the differential pressure liquid level transmitter. As long as the density and other parameters of the measured medium meet the requirements of the nameplate, generally no adjustment is required.
If the customer needs to adjust the range or zero position, please adjust according to the following methods. Assuming that the range of the differential pressure liquid level transmitter is 0 ~ 10 meters:
- Unscrew the protective cover of the differential pressure liquid level transmitter. It can be adjusted by connecting an external standard 24VDC power supply and ammeter (requires accuracy of 0.2% or above).
- When there is no liquid in the differential pressure liquid level transmitter. Adjust the zero potentiometers. Make it output a current of 4mA.
- Pressurize the differential pressure liquid level transmitter to full scale (10 meters). Adjust the full-scale resistor. Make it output a current of 20mA.
- Repeat the above steps two or three times until the signal is normal.
- Please input 25%, 50%, and 75% signals to check the error of the differential pressure liquid level transmitter.
- For non-aqueous media. Differential pressure level transmitters are calibrated with water. It should be converted according to the pressure generated by the actual density of the medium. For example, when the medium density is 1.3, the 1.3m water level should be used to calibrate the 1m range.
- After adjustment, tighten the protective cover.
- The verification cycle of the differential pressure liquid level transmitter is once a year.
- HART intelligent differential pressure liquid level transmitter of Sino-Inst instrument can be selected. It is convenient to adjust the range of the differential pressure liquid level transmitter.
Extended reading: How to calibrate HART pressure transmitters
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Sino-Inst (drurylandetheatre.com) offers over 20 DP transmitters for liquid level, pressure, flow, and density measurement. Differential pressure (DP) level transmitters are suitable for measuring water and other liquid levels.
We are a differential pressure level transmitter supplier, located in China. Our products are widely exported to the United States, Australia, Singapore, Indonesia, etc. You can ensure product safety by selecting from our products, including IOS9000, and… certification.
Of course, in addition to differential pressure transmitters, pressure transmitters can also be used to measure the liquid level in open tanks. If you need to purchase Level Transmitters or have related technical questions, please feel free to contact our sales engineers!
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Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.