Absolute pressure transmitters measure the difference between vacuum and measured pressure. Absolute pressure (AP) transmitter is a measure of the ideal (complete) vacuum.
Absolute pressure transmitters, also known as absolute pressure transducer,
and absolute pressure sensor. Measure absolute pressure relative to full vacuum. In contrast, pressure measured relative to atmosphere is called gauge pressure. All absolute pressure measurements are positive. The readings produced by absolute pressure sensors are not affected by atmosphere. When the pressure corresponds to the ideal vacuum, the absolute pressure transmitter will produce a 4mA output signal.
Sino-Inst offers a variety of pressure senors for industrial pressure measurement. If you have any questions, please contact our sales engineers.
Absolute Pressure Transmitter Features
- Sensor Type : Industrial Pressure Transducers
- Full function buttons on site
- Pressure ranges: 0 … 1 mbar up to 0 … 600 bar
- Output/Span : 0 – 10 V, 0 – 5 V, 1 – 5 V, 10 mV/V, 4 – 20 mA, HART
- Pressure Port/Fitting : 1/2 MNPT, 1/4 FNPT, 1/4 MNPT, 1/8 MNPT
- Operating Temperature Range: -40 – 85 °C [ -40 – 185 °F ]
Extended reading: How to calibrate HART pressure transmitters
Specifications of Absolute Pressure Transmitter
| Model | Transmitter type |
| SI-1301GP | Pressure transmitter |
| SI-1301AP | 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 output 4-20mAdc+HART signal，Full function buttons on site |
| F | MODBUS-485 signal |
| 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 |
| D0 | The discharge valve is at the end |
| D1 | The side discharge valve is on the upper part |
| D2 | The side discharge valve is on the upper part |
| C02 | M20 x 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 |
| X1 | Oil ban |
| Gd | Measure the gold-plated membrane box |
| Da | Flameproof ExdIIBT5Gb;(explosion-proof certificate no. : CE16.1163) |
| Fa | Intrinsically safe ExiaIICT4 / T5 / T6Ga;(explosion-proof certificate no. : CE15.2354X) |
| Code | 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 |
Read more about: Common Units Of Pressure
What is the absolute pressure?
The pressure acting on the surface of object is called “absolute pressure”. The absolute pressure value starts with absolute vacuum.
The absolute pressure sensor measures the pressure relative to the high vacuum reference. The high vacuum reference is sealed behind its sensing diaphragm. The vacuum must be negligible compared to the pressure to be measured.
Sino-Inst’s absolute pressure sensor provides a pressure range of 1 bar or even 700 mbar. Most electronic pressure sensors measure pressure based on the deformation of the diaphragm.
For Gauge pressure sensors, One side of the diaphragm is exposed to process pressure, while the other side is exposed to ambient. This means that the pressure is actually the difference between the process pressure and atmospheric.
For absolute pressure sensors, the side of the sensor that is not in contact with the pressure medium is exposed to a permanently sealed absolute vacuum chamber. The deformation of the diaphragm is not affected by atmospheric. Because it uses a sealed vacuum as a reference point and zero point.
What is absolute pressure transmitter?
Absolute pressure (AP) transmitter measure relative to perfect (full) vacuum pressure (absolute zero pressure).
Therefore, AP transmitters are not affected by fluctuations in the local atmosphere.
All absolute pressure measurements are positive.
The letter ‘a’ or the abbreviation ‘abs’ in the unit of measure
(i.e., inH₂O(abs) or psia) indicates an absolute pressure measurement.
Any critical storage and delivery (toxic gases) will change due to atmospheric conditions. So these systems must be accurate and use static references. Absolute pressure transmitters are used in applications where the pressure of a gas or liquid is isolated from changes in atmosphere. For example, when testing a sealed pressure vessel for leaks for a long time.
How do absolute pressure sensors work?
The absolute pressure transmitter is mainly composed of two parts. One part is directly connected to the side to be measured. The other side is designed as an absolute vacuum reference chamber. This makes the two compartments form Absolute pressure. When the pressure on both sides is inconsistent, the difference signal will be transmitted through a special transmission line. The computer system in the background can calculate the difference. The pressure value on the measured side is directly displayed.
Applications for Absolute Pressure Sensors
Absolute pressure sensors and absolute pressure gauges are commonly used in industrial high-performance vacuum pumps that require monitoring.
For example, it is used to vacuum package medical products in a clean environment. To ensure that hospitals and doctors are provided with hygienic and bacteria-free delivery.
In the food industry, when the highest possible vacuum is needed to prevent oxygen from degrading perishable food, vacuum packaging can be used, which greatly extends the flavor and shelf life of the product.
For example, in meat packaging, a vacuum that meets the requirements must be generated, so that the longest shelf life can be safely guaranteed.
Pressure sensors affected by the atmosphere cannot monitor the high end of the vacuum.
Applications that require true absolute pressure sensors and gauges can also be found in scientific laboratories, universities, military and aerospace industries.
Applications requiring true absolute pressure sensors and gauges, can also be found in scientific laboratories, universities, the military, and the aviation industry.
Sino-Instrument supplies Direct Mount Pressure / Absolute Pressure Transmitter.
Absolute pressure transmitter calibration
- First make a 4-20mA fine adjustment. It is used to calibrate the D / A converter inside the transmitter. Because it does not involve sensing components, no external pressure signal source is required.
- Do a full fine-tuning again. Make the 4-20mA, digital reading coincide with the actual applied pressure signal. Therefore, a pressure signal source is required.
- Finally, re-quantify the range. By adjusting the analog output 4-20mA and the external pressure signal source. Its function is exactly the same as the zero (Z) and range (R) switches on the transmitter shell.
Gauge pressure VS absolute pressure
1. Gauge pressure:
Gage pressure refers to pipeline pressure. It refers to the pressure measured with pressure gauges, vacuum gauges, U-shaped tubes and other instruments. It is also called relative pressure. “Gage pressure” starts from atm.
2. Absolute pressure:
The pressure directly acting on the surface of the container or object is called “absolute pressure”. The absolute pressure value starts with absolute vacuum.
3. Relationship:
Absolute pressure actually refers to the gauge pressure plus the local atm.
Absolute pressure = gauge pressure + 1 atm
If it is in MPa, absolute pressure = gauge pressure + 0.1MPa
Gauge pressure = absolute pressure-atm
Vacuum = atm-absolute pressure
The pressure measured on the basis of absolute vacuum is the absolute pressure. The pressure measured on the basis of atm is the gauge pressure or the degree of vacuum. G behind the pressure indicates gauge pressure, A indicates absolute pressure.
The gauge pressure g = gauge refers to the pressure indication of the pressure gauge on the system. It can also be simply understood as putting a pressure gauge under atm, at which time the pressure gauge displays zero. The gauge pressure at this time is displayed as 0. If the pressure of this gauge pressure rises, the rising value is the gauge pressur
Read more about: Absolute Pressure Vs Gauge Pressure Measuring Instruments
Absolute pressure transmitter VS Gauge pressure transmitter
Absolute pressure transmitter
Absolute pressure transmitter can realize absolute pressure measurement in equipment such as degassing system, distillation tower, evaporator and crystallizer, and allows pressure under 10Mpa. The δ chamber side of the absolute pressure transmitter receives the measured absolute pressure signal. The other side is sealed into a high vacuum reference chamber. Then convert it into 4 ~ 20mA DC signal output.
Gauge pressure transmitter
A gauge pressure transmitter in the general sense is mainly composed of a load cell sensor (also called a pressure sensor), a measurement circuit and a process connection. It can convert the physical pressure parameters such as gas and liquid felt by the load cell sensor into standard electrical signals (such as 4 ~ 20mADC, etc.), and provide secondary indicators such as alarm indicators, recorders, and regulators for measurement and indication. And process regulation.
Sino-Inst is Chinese manufacturer of absolute pressure transmitters.
SMT3151ap absolute pressure transmitters, are our mian products, which are widely used in India, US, South Africa, and other countries.
Contact us any time, if you need the quotation or technical support.
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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.