Pressure transmitters and transducers with industry-leading performance help improve operations in a wide range of industries
What is a pressure indicator transmitter?
Pressure indicator transmitters are industrial instruments, which has a digital display for providing a local indication of pressure indicating, and a 4-20 mA output pressure transmitter (which is also called the smart pressure gauge), for sending an analog signal to control & monitor instrumentation. The built-in digital indicators can be scaled via push buttons or change pots, to any pressure unit or a 0-100% full scaling. No additional external supply is required, since the digital indicator is powered by the 4-20mA current loop, from the pressure transmitter.
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.
Updated April 2026 — By Sino-Inst Engineering Team
A pressure transmitter converts the mechanical force of fluid or gas pressure into an electrical signal — typically 4–20 mA or a digital protocol like HART. That signal goes to a PLC, DCS, or SCADA system for monitoring, control, and alarms.
Pressure transmitters are found in nearly every process industry: oil and gas, water treatment, chemical plants, power generation, HVAC, and food processing. They measure gauge pressure, absolute pressure, differential pressure, or vacuum — depending on the application.
This guide explains how they work, the five main sensing technologies, signal output options, and how to select the right one for your application.
How Does a Pressure Transmitter Work?
Every pressure transmitter has three functional blocks:
Sensing element — A diaphragm, piezo crystal, or capacitive cell that physically deforms under pressure.
Signal conditioning — Electronics that convert the raw sensor output (resistance change, charge, or capacitance shift) into a proportional electrical signal.
Output stage — Sends the conditioned signal to the control system via analog (4–20 mA) or digital (HART, Modbus, Profibus) protocol.
The process medium pushes against a diaphragm. The diaphragm deflects — maybe 0.001 mm at full scale. That tiny deflection changes the electrical properties of the sensing element (strain, capacitance, or piezoelectric charge). The transmitter electronics measure the change, compensate for temperature, linearize the output, and produce a calibrated signal.
5 Pressure Sensing Technologies
1. Piezoresistive (Diffused Silicon)
A silicon diaphragm has strain gauges diffused directly into its surface. When pressure deflects the diaphragm, the resistance of these gauges changes — a phenomenon called the piezoresistive effect. A Wheatstone bridge circuit converts this resistance change into a voltage proportional to pressure.
This is the most common sensing technology. It covers ranges from 0–100 Pa to 0–100 MPa. Accuracy is typically ±0.25% to ±0.1% FS. Temperature range: -40 to +125°C. Cost-effective and reliable for general industrial use.
2. Capacitive
Two metal plates sandwich a sensing diaphragm. Pressure deflects the diaphragm, changing the gap between the plates and therefore the capacitance. The electronics measure this capacitance change with high precision.
Capacitive sensors dominate in differential pressure measurement and high-accuracy applications. Accuracy reaches ±0.075% FS in premium models. They handle low pressures (down to 0.1 kPa) better than piezoresistive types. This is the technology used in Rosemount 3051, Yokogawa EJA, and other top-tier DP transmitters.
3. Ceramic (Thick-Film)
A ceramic (Al₂O₃) diaphragm has thick-film resistors printed on its back surface. Pressure bends the ceramic, changing the resistance. The ceramic itself acts as the isolation diaphragm — no fill fluid needed.
Ceramic sensors excel in corrosive media because the sensing element contacts the process directly without an oil-filled cavity. They resist chemical attack from most acids and alkalis. Temperature range: -40 to +135°C. Cost is lower than stainless steel models. Common in water treatment, chemical dosing, and food-grade applications.
4. Piezoelectric
Quartz or tourmaline crystals generate an electric charge when mechanically stressed. The charge is proportional to the applied force. A charge amplifier converts this into a usable voltage signal.
Piezoelectric sensors respond extremely fast — microsecond rise times. They measure dynamic pressure events: combustion chamber pulsations, hydraulic hammer, blast waves. They cannot measure static pressure because the charge leaks away over time. Not used for steady-state process monitoring.
5. MEMS (Micro-Electro-Mechanical Systems)
MEMS pressure sensors use semiconductor fabrication techniques to build the diaphragm and sensing elements on a silicon chip. The result is an extremely small, low-power sensor with good accuracy.
MEMS technology has driven down the cost and size of pressure transmitters. Most consumer and automotive pressure sensors are MEMS-based. In industrial applications, MEMS sensors appear in compact transmitters, portable calibrators, and IoT-enabled wireless pressure monitors.
Types of Pressure Transmitters
Pressure transmitters are classified by what pressure reference they use:
Type
Measures
Reference
Typical Use
Gauge Pressure
Pressure above/below atmosphere
Atmospheric (vented)
Pipe pressure, tank pressure, pump discharge
Absolute Pressure
Pressure above perfect vacuum
Sealed vacuum
Barometric, vacuum systems, altitude
Differential Pressure
Difference between two pressures
Second pressure port
Flow measurement, filter monitoring, level
Vacuum/Compound
Pressure below atmosphere or both sides
Atmospheric
Vacuum pumps, HVAC, process vacuum
Hydrostatic (Submersible)
Liquid column pressure = level
Atmospheric (vented cable)
Tank level, well depth, open channel
Differential pressure transmitters are the most versatile. With an orifice plate or Venturi, a DP transmitter measures flow. Connected to the top and bottom of a tank, it measures level. Across a filter, it monitors clogging. One instrument, three measurements — that is why DP transmitters account for roughly 40% of all pressure transmitter sales worldwide.
Signal Output Options
Output
Signal Range
Max Distance
Best For
4–20 mA (analog)
4 mA = zero, 20 mA = full scale
1–2 km
Universal, noise-immune, long runs
0–10 V (voltage)
0 V = zero, 10 V = full scale
<15 m
Short cable runs, lab/test
HART (hybrid)
4–20 mA + digital overlay
1–2 km
Diagnostics + analog backup
Modbus RS485
Digital, multi-drop
1.2 km
Multiple transmitters on one cable
Millivolt (mV)
0–100 mV typical
<3 m
OEM integration, low cost
For most industrial installations, 4–20 mA with HART is the standard. The analog signal is immune to electrical noise and works with every PLC on the market. HART adds digital diagnostics — you can read sensor temperature, configure range, and check health without disconnecting wires. For new digital plants, Modbus or Profibus PA eliminates analog entirely.
How to Select a Pressure Transmitter
Start with these six parameters. Get them wrong and nothing else matters.
Pressure type — Gauge, absolute, differential, or vacuum? This determines the transmitter category.
Pressure range — Select a range where your normal operating pressure falls between 25% and 75% of full scale. Oversizing reduces accuracy; undersizing risks damage.
Process media — What fluid contacts the diaphragm? Corrosive chemicals need Hastelloy or tantalum diaphragms. Food-grade requires sanitary tri-clamp connections. High-viscosity fluids need flush-mount diaphragms.
Temperature — Both process temperature and ambient temperature. Standard transmitters handle -40 to +85°C process temp. High-temp models reach +150°C or higher with remote seals. Electronics rarely survive above +85°C ambient without cooling.
Accuracy — General process control: ±0.5% FS is sufficient. Custody transfer or fiscal metering: ±0.075% FS or better. Remember — accuracy specs apply only at reference conditions. In the field, temperature drift and installation effects add error.
Output and protocol — Match your control system. Most PLCs accept 4–20 mA. HART adds diagnostics at no extra wiring cost. Digital protocols (Modbus, Profibus) need compatible I/O cards.
Other factors: hazardous area certification (ATEX, IECEx, FM), ingress protection (IP65 minimum for outdoor, IP68 for submersible), mounting style (direct, remote seal, flush diaphragm), and response time.
What is the difference between a pressure transmitter and a pressure transducer?
Both convert pressure into an electrical signal. A transducer outputs a raw signal (millivolt or resistance change) that needs external conditioning. A transmitter has built-in electronics that output a standardized signal (4–20 mA, 0–10 V, or digital). In practice, most people use the terms interchangeably. If you need a plug-and-play device for a PLC, you want a transmitter.
How accurate are pressure transmitters?
Standard industrial transmitters achieve ±0.25% of full scale. Premium models (like capacitive DP transmitters) reach ±0.075% or ±0.04% FS. Accuracy specifications apply at reference conditions — in the field, temperature drift, vibration, and mounting position add error. Total performance specs give a more realistic picture than accuracy alone.
Can a pressure transmitter measure flow?
A differential pressure transmitter can measure flow when paired with a primary element — an orifice plate, Venturi tube, or flow nozzle. The DP transmitter measures the pressure drop across the restriction. Flow rate is proportional to the square root of ΔP. This is the basis of all DP flow measurement per ISO 5167.
What is the typical lifespan of a pressure transmitter?
10 to 20 years in normal service. Silicon-based sensors have no moving parts to wear out. The electronics and seals age first. Harsh conditions (high temperature, corrosive media, frequent pressure cycles) shorten life. Annual calibration checks catch drift before it causes process problems.
How do I wire a pressure transmitter?
A 2-wire 4–20 mA transmitter needs only two wires — power and signal share the same loop. Connect the positive terminal to the power supply (+), run the negative terminal through your PLC analog input, then back to the power supply (−). Supply voltage is typically 12–36 VDC. For detailed diagrams, see our pressure transmitter wiring guide.
What is the price range for pressure transmitters?
Entry-level OEM sensors: $30–$80. Standard industrial gauge transmitters: $150–$500. High-accuracy DP transmitters: $500–$2,000+. Premium brands (Rosemount, Yokogawa) cost more; equivalent Chinese-manufactured units offer 70–80% of the performance at 30–40% of the price. For specific pricing, contact our sales team.
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About the Author Sino-Inst Engineering Team — With over 20 years of experience in industrial process instrumentation, our team specializes in flow, level, pressure, and temperature measurement solutions. We have completed 10,000+ installations across oil & gas, water treatment, chemical, and power generation industries worldwide. Our engineers hold certifications in ISA, IEC, and ISO standards. For technical questions, contact us at rfq@sino-inst.com or call +86-180 4861 3163.
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.
Pressure transmitter calibration is what you need to dobefore you install the pressure transmitters. Also called pressure transducer calibration, or pressure sensor calibration.
In this article, we will share pressure transmitter calibration using hart communicator.
Pressure transmitters used in the process industries are very durable and reliable instruments.
Even so, they still require periodic maintenance and calibration to ensure optimal performance.
Before we start to calibrate the pressure transmitter, we should know:
What is span in pressure transmitter?
Fig. showing span and zero adjustment
Span value: The difference between two minimum value and maximum value of readings is known as a span value.
As shown in fig. below span = 20mA – 4mA
Zero Value: The value of readings at zero lines (Y-axis) is known as zero value as shown in the figure.
How Often Should You Calibrate a Pressure Transmitter?
Pressure transmitters require regular maintenance and calibration to ensure optimum performance.
There are no specific rules for the calibration of pressure transmitters. However, this depends on the regulations the company must comply with and the purpose of the calibration. Examples include safety specifications, application requirements, process conditions or as part of standard maintenance.
General industry practice is to calibrate pressure transmitters every 1 to 3 years based on the above conditions.
If it is found that there are obvious errors, or it is more important, the calibration cycle can be shortened.
Once you have established the calibration interval and MPE, you are ready to perform the actual calibration procedure on your pressure transmitter.
The best-practice recommendation is:
Mount the transmitter in a stable fixture free from vibration or movement.
Exercise the sensor or membrane before performing the calibration.
This means applying pressure and raising the level to approximately 90 percent of the maximum range. For a 150 psi cell that means pressurizing it to 130–135 psig. Hold this pressure for 30 seconds, and then vent. Your overall results will be much better than if you calibrate “cold.” cent of the maximum range. For a 150 psi cell that means pressurizing it to 130–135 psig. Hold this pressure for 30 seconds, and then vent. Your overall results will be much better than if you calibrate “cold.”
Perform a position zero adjustment (zero the transmitter).
This is important because the orientation of the fixture used for calibration may be different than the way the transmitter is mounted in the process. Failing to correct for this by skipping this step can result in nonconformance. You may like: Magnetostrictive level transmitters Magnetostrictive level sensor
Begin the Pressure Transmitter Calibration procedure.
Typically this means three points up (0 percent/50 percent/100 percent) and then three points down. The 4–20 mA output should be 4 mA, 12 mA, and 20 mA at the three points (or the correct digital values for a smart transmitter). Each test point should be held and allowed to stabilize before proceeding to the next. Normally that should take no more than 30 seconds. You can use more points if you require higher confidence in the performance of the instrument.
Compare the results of your pressure transmitter to your reference device.
Document the results for your records.
Pressure transmitter calibration formula
There is a formula that we can easily use to convert most (or all) units utilizing 4 to 20 mA signal to mA units.
There are others out there but this is the simplest I know.
Below is a simple formula for pressure to current conversion.
For example:
the range is : 0 to 10 Bar
Full range = 10 Bar
Displayed or measured value: 7 Bar
15.2 mA is the equivalent current value of a 7 Bar pressure.
Apply 0% pressure as per LRV with handheld test pump and check multimeter if it is not 4ma adjust the zero pot in the transmitter and correct transmitter output to 4ma
Apply 100%pressure as per the URV and correct 20ma in multimeter by adjusting span pot in the transmitter
Repeat these steps to rectify the error.
In case of SMART Transmitter
We have to use HART communicator, connect the communicator with the transmitter select the HART Communicator Menu for lower range value trim and upper range value trim.
Basic Set up – Calibration – Zero Trim/Sensor Trim —Lower/Upper range value trims.
Take the transmitter on line. Ensure there is no leak
a small example of five-point calibration is given below
Low range value=0psi
upper range value=200psi
This calibration can work for Rosemount 3051 calibration.
Preparing for Field Calibration of Differential Pressure Transmitters
The usual practice is to disassemble the joint of the pressure guiding tube and the differential pressure transmitter, and then connect to the pressure source for calibration. It is troublesome and labor-intensive. The most worry is that there will be leakage or the pressure guiding pipe will be broken when disassembling and assembling the joint.
No matter what type of differential pressure transmitter, the positive and negative pressure chambers have exhaust, drain valves or cocks. This provides convenience for on-site calibration of the differential pressure transmitter, so that it can be calibrated without removing the pressure guiding tube. Differential pressure transmitter.
But make a fitting with the same thread as the vent, drain valve or cock.
When the differential pressure transmitter is calibrated, first close the positive and negative valves of the three-valve group. Open the balance valve, and then loosen the exhaust and drain valves to vent.
Then use a self-made connector to replace the vent, drain valve or cock connected to the positive pressure chamber. The negative pressure chamber is kept unscrewed, allowing it to vent to the atmosphere.
The pressure source is connected with the self-made joint through the rubber tube. Close the balance valve. And check the air circuit sealing.
Then connect the ammeter (voltmeter) and the hand-operated communicator into the differential pressure transmitter circuit, and start the calibration after power-on and preheating.
Field Calibration of Conventional Differential Pressure Transmitters
First adjust the damping to zero state, first adjust the zero point. Then add full pressure to adjust the full scale, so that the output is 20mA. The adjustment should be fast in the field. Here is a quick adjustment method for zero point and span.
When the zero point is adjusted, it has almost no effect on the full scale, but when the full scale is adjusted, it has an effect on the zero point. When there is no migration, the effect is about 1/5 of the range adjustment amount, that is, the range is adjusted upward by 1mA. The zero point will move upward by about 0.2mA ,vice versa.
E.g: The input full scale pressure is 100kPa, the reading is 19.900mA. The range-adjusting potentiometer makes the output 19.900+(20.000-19.900)×1.25=20.025mA, and the range increases by 0.125mA. Then the zero point increases by 1/5×0.125=0.025, and the zero-point potentiometer makes the output 20.000mA.
After the zero point and full scale adjustment are normal, check the middle scales, and make fine adjustments if they are out of tolerance. Then carry out the adjustment work of migration, linearity and damping.
Smart Differential Pressure Transmitter Field Calibration
The intelligent differential pressure transmitter is between the input pressure source and the output 4-20mA signal. In addition to machinery and circuits, there is also a microprocessor chip that operates on the input data.
Therefore, the field calibration method of intelligent differential pressure transmitter is different from that of conventional differential pressure transmitter.
The differential pressure liquid level transmitter has been calibrated according to customer requirements in terms of range, accuracy, linearity and other parameters. And mark the range, accuracy, etc. on the nameplate of the differential pressure liquid level transmitter. As long as the parameters such as the density of the measured medium meet the requirements of the nameplate, there is usually no need to adjust.
If the customer needs to adjust the span 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 back cover of the differential pressure liquid level transmitter, connect an external standard 24VDC power supply and an ammeter (requires an accuracy of 0.2% or higher) to adjust.
When there is no liquid in the differential pressure liquid level transmitter. Adjust the zero point potentiometer so that the output current is 4mA.
Pressurize the differential pressure liquid level transmitter to the full scale (10 meters). Adjust the full-scale resistor so that the output current is 20mA.
Repeat the above steps two or three times until the signal is normal.
Please input 25%, 50% and 75% respectively to check the deviation of the differential pressure liquid level transmitter.
For non-water media, when the differential pressure liquid level transmitter is calibrated with water, it should be converted according to the pressure generated by the actual use of the medium density. For example, when the density of the medium is 1.3, the 1.3m water level should be used to calibrate the 1m range.
After adjustment, tighten the back cover.
The calibration cycle of the differential pressure liquid level transmitter is once a year.
The HART intelligent differential pressure liquid level transmitter of Sino-Inst can be selected, which is convenient to adjust the range of the differential pressure liquid level transmitter.
Learn more about Pressure Transmitter Calibration
When you buy a pressure transmitter, for example, you have the instrument range, which is the pressure range the device can support.
This range covers the overpressure that might occur in the device.
The measuring range covers the values where the transmitter works properly, omitting the overpressure zone.
The lower range limit (LRL) and upper range limit (URL) define this range.
Inside the measuring range, you’ll find the calibration span, the range in which your device will be working, depending on your application.
The calibration span covers the difference between your upper range value (URV), the maximum value your transmitter can read, and the lower range value (LRV), the minimum value the device can read.
So there you go!
You should also know that each instrument has a minimum and maximum calibration span it can support.
If you go below or over these limits, you’ll lose accuracy in your readings.
Make sense? Let me give you an example, just to make it clearer.
Let’s say you want a pressure transmitter with a measurement range of -100 to 200 kilopascals (kPa).
This device can measure pressures as low as -100 and as high as 200 kPa.
If your application just requires pressure between -20 to 50 kpa, then this will be your calibration range.
Your calibration span is the URV-LRV.
By the numbers: 50 – (-20) = 70 kPa.
Therefore, you get a calibration span of 70 kPa, which falls inside the span range (10 to 200 kPa).
A pressure transmitter or pressuresensor is a device that measures pressure in a liquid, fluid, or gas.
Pressure transmitters are commonly used to measure the pressure inside of industrial machinery, in order to alert the user before a catastrophe occurs.
Yes, pressure transducers require calibration. Pressure transducers are used in many applications to provide accurate, real-time data on how systems work. Calibration is critical to maintaining the accuracy of pressure sensors. And it’s not a one-time process.
If the sensor deviates from its specified pressure range, it may cause erroneous pressure readings. This results in degraded device performance and possible security issues.
Calibration allows users to be completely confident that their pressure transducers are performing correctly and accurately measuring the desired pressure range.
If you cannot find an answer to your question in our Pressure Transmitter Calibration you can always contact us and we will be with you shortly.
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Conclusion:
It is normal for the pressure transmitter to have a certain error. But if the error is too large, it needs to be calibrated. There are two types of Pressure Transmitter Calibrations: conventional method and intelligent calibration. no matter where Kinds of preparations must be done before calibration, and then calibrate and debug through the handheld operator.
There are no mandatory fixed requirements for Pressure Transmitter Calibration. Generally, enterprises can formulate them by themselves. Normally, they can be calibrated once a year. Crucially, the calibration cycle can be shortened.
About how to calibrate the pressure transmitter, and what needs to be paid attention to during the process of Pressure Transmitter Calibration. If you still have questions, please feel free to contact our 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.
