Pressure Transmitter

The pressure transmitter consists of a sensor to measure the physical parameter of pressure and a transducer (transducer) to convert this parameter into an electrical signal. There are about 50 different types of pressure transmitters, each of which works differently from the other, so it is not possible to list all of these methods.

Types of pressure transmitters

Pen pressure transmitter

These transmitters are similar to pen batteries and car spark plugs and are very useful due to their small size and pen appearance. The pen pressure transmitter has a flat metal plate at its tip that acts as a pressure sensor and these transmitters are connected to the tank or pressure measurement system by the threaded end.

Diaphragm pressure transmitter

These transmitters have a diaphragm plate that changes its shape with the pressure changes of the diaphragm plate and are closed as pen transmitters or in a different way on tanks. Diaphragm pressure transmitters are usually made of stainless steel or polymer composites, and depending on the material they are made of, they have different ability to measure pressure.

Differential pressure transmitter or differential pressure transmitter

These transmitters are used to measure the pressure difference between two tanks or two sides of a pipe. In these transmitters, metal sensors or diaphragm curtains are used to show pressure changes.

Explosion-proof pressure transmitter

Anti-explosion pressure transmitters are used in petrochemical industries and refineries, as well as ammonia production plants, where the possibility of sparking is very high. These transmitters minimize the possibility of sparking.

Industrial pressure transmitter

Industrial pressure transmitters are designed to measure pressure in the high pressure range and various applications.

Smart pressure transmitter

These transmitters have high accuracy and speed, and this feature causes more accurate control of the process.

Pressure transmitter with display

In these pressure transmitters, a screen is used to display the pressure in real time. Also, these transmitters have the ability to send pressure measurement values ​​to the control room. Basically, these transmitters are used in environments where the presence of the operator is possible.

Pressure measuring element in pressure transmitter

Various elements can be used to measure the pressure in the transmitter, each of which has advantages and disadvantages; Among the elements of pressure measurement, the following can be mentioned:

• Strain is confused
• capacitive
• Piezoelectric
• Piezoresistive
• Linear Variable Differential Transformer (LVDT)

Strain is confused

Strain gauge sensors have a DC voltage output, and the disadvantages of these pressure sensors are their low sensitivity and low temperature range.

Capacitive sensor

These sensors have linear output, low hysteresis and good stability.

Piezoelectric sensor

These sensors have small dimensions with strong structure, wide temperature range and fast response. Piezoelectric sensors have disadvantages such as high temperature sensitivity, high output impedance and AC voltage output.

Piezoresistive sensor

These sensors have DC voltage output, small dimensions, fast response time and high sensitivity; But it is less sensitive to temperature changes.

Application of pressure transmitter

By using other peripheral equipment, such as orifice plates, it can be used to measure other parameters. Among the applications of pressure transmitter, the following can be mentioned.

• Pressure measurement: Pressure sensors are directly used in the automotive industry, meteorology and cases where pressure is measured directly.
• Flow measurement: Venturi relationship with pressure is used to calculate flow. In this method, the pressure difference has a direct relationship with the flow rate passing through the tube.
• Measuring height above sea level: pressure transmitters are used in cases where pressure changes are measured relative to sea level, such as applications in airplanes, satellites, and meteorology, etc.
• Leakage test: By measuring the pressure and pressure changes in a period of time or by comparing the pressure of the desired system with a system that has a certain amount of leakage and calculating this pressure difference, the amount of leakage is calculated.
• Measuring height and depth: The level of liquids is proportional to pressure, and pressure transmitters are used to measure the condition of objects in water, such as submarines, or the level of liquid height in tanks.

Pressure transmitter output

The pressure transmitter measures the pressure and converts the measured pressure value into an electrical signal. The output of the transmitter is as follows:

• Transmitter with current signal output

Current output in pressure transmitters is 4 to 20 milliamps. These transmitters are very popular due to easy troubleshooting and long life of the measuring device.

• Transmitter with PROFIBUS signal output

Profibus output is a commonly used communication standard and is an abbreviation of the word Process Fieldbus and is widely used in industrial automation and control and safety systems.

• Transmitter with Hart signal output (HART)

HART stands for Remote Control Transducer and stands for Highway Addressable Remote Transducer. In the HART protocol, digital signals are placed on the analog signal of 4 to 20 mA without any interference. The digital signal communicates with a 4 to 20 mA signal without interruption, at a speed of 1200 bits per second. The digital signal includes the status of the device, detection of additional measured or calculated values, etc. In general, through two analog and digital communication channels, a complete, low-cost and flawless communication is provided with a simple configuration.

• Transmitter with RS232 and RS485 output

In this protocol, data is transferred in bits per second.

• Transmitter with parallel output

Multiple bits are shifted simultaneously.

How to choose a pressure transmitter

Things to consider when choosing a pressure transmitter are as follows:

• Accuracy of the transmitter
• Type of pressure transmitter
• Pressure measurement range
• Transmitter output type
• Type of pressure (absolute or relative)
• Environmental conditions

Pressure transmitter brands

• Hagler pressure transmitter
• Synthesis pressure transmitter
• Delta pressure transmitter
• Rosemount pressure transmitter
• Chlorine pressure transmitter
• Jahavi pressure transmitter
• Microsensor pressure transmitter
• Madeco pressure transmitter
• Yokogawa pressure transmitter
• Siemens pressure transmitter
• Anders Hauser pressure transmitter
• Wicca pressure transmitter
• Pickens pressure transmitter
• ABB pressure transmitter
• Vega pressure transmitter
• Trafag pressure transmitter
• Curl pressure transmitter
• Danfoss pressure transmitter