Pressure Transmitters and Transducers

There are different types of pressure measurement based on the principle of operation: gauge pressure, absolute pressure, and differential pressure.

• Gauge Pressure

It takes the atmospheric pressure as the reference point. Since the atmospheric pressure may vary according to different locations, a gauge pressure sensor is needed to ensure accurate pressure measurement. Generally, a gauge pressure sensor has a vented tube connecting atmospheric pressure as a reference point to measure the media pressure.

• Absolute Pressure

It takes the perfect vacuum as the reference point. Absolute pressure measurement is commonly used in vacuum systems and applications where zero pressure is crucial. 

A formula shows the difference between gauge pressure and absolute pressure: Absolute pressure = gauge pressure + atmospheric pressure

• Differential Pressure

The pressure difference between two points or systems is known as differential pressure. A differential pressure transmitter is a specific differential pressure in that one pressure is always atmospheric. 

Main Components of Pressure Transmitter and Transducer

The pressure transmitter is also known as a pressure transducer in some areas. It is a device that measures and transmits a signal proportional to the pressure applied. The structure of a pressure transmitter can vary depending on the application, but typically includes the following main components:

• Sensing Element

This is the essential component for pressure measuring that converts the applied pressure into an electrical signal. 

• Circuit Board Chip

Circuit board chips are divided into analog chips and signal conditioning chips. This component amplifies or processes the electrical signal into a transmittable, unified standard signal. It can be a 4-20 mA current loop, voltage output and digital outputs.

• Housing

The sensing element and circuit board chip are enclosed in a housing to protect them from environmental factors like vibration, shock, and moisture. Housing with optional materials such as stainless steel 316L, SS 304, Hastelloy C, Tantalum, etc., according to the different working environments. 

• Electrical Connection

These connectors link the transmitter to the power supply and other instrumentation in the control system. B1 4-pin Plug Connector, B2 Cable Connection, and other types are available. The choice of electrical connection depends on factors such as the current carrying capacity, voltage level, application requirements, and industry standards.

• Process Connection

It involves the physical connection between the pressure transmitter and the process piping or equipment. There are several types of process connections commonly used in industrial applications, including thread connection, flanged connection, clamp connection, etc.

The choice of process connection depends on factors such as the process fluid, pressure, temperature, pipe size, and compatibility with the instrument. It is important to select the appropriate process connection to ensure accurate measurement, reliable operation, and safety.

Differences Between Digital and Analog Output of Pressure Transmitters

According to the characteristics of the output signal, the output mode of the pressure transmitter has analog output and digital output.

• Analog Pressure Transmitter

Common pressure sensor analog outputs include 4-20mA, 0-5V/10V DC, 0.5-4.5V DC, etc. In practical applications, users can more conveniently collect, process, and restore analog signals.

In maintaining the output signal's consistency, the analog pressure transmitter is more convenient to replace and maintain on-site. Compared with digital output products, the system response speed of analog output products is faster. Therefore, in special working conditions with higher requirements on frequency response, analog output pressure transducers are more suitable.

• Digital Pressure Transmitter

Common digital outputs include RS485, I²C, HART, etc. Its system cost is lower when solving multi-point measurement applications. Compared with analog output products, the digital pressure transmitter is convenient for networking and conducive to online adjustment.

Among many digital products, RS485-Modbus is one of the most widely selected. The product has strong anti-interference ability and long transmission distance. I²C hardware is low-cost, fast, and has high data volume.

MicroSensor provides digital and analog output signal pressure transducers depending on your system compatibility, communication requirements, noise immunity, and the level of accuracy needed for the application. 

Common Communication Protocols for Pressure Transmitters

Commonly used pressure transmitter communication protocols include 4-20mA, MODBUS, HART, etc. These communication protocols enable data transmission between the transmitter and equipment and control systems. 

• 4-20mA Analog Signal

4-20mA converts pressure signals into current signals for transmission. 4mA represents zero pressure, and 20mA represents full pressure. By measuring the current signal output by the transmitter, the current pressure value can be determined. It is suitable for long-distance transmission, but lacks two-way communication capabilities.

• MODBUS

MODBUS is a serial communication protocol widely used in industrial automation. The pressure transmitter uses the MODBUS protocol to transmit a variety of data, including real-time pressure values, equipment status, alarm information, etc. This protocol has high flexibility and scalability and can be adapted to different control systems.

• HART

HART superimposes digital communication on top of the 4-20mA analog signal. It enables configuration and diagnostic capabilities remotely. The communication protocol is suitable for industrial applications where both analog and digital signals are needed.

Why is Industrial Pressure Measurement Important?

Pressure measurement benefits the following aspects in process industry:

• Safety: Pressure monitoring in industrial environments maintains safe operating conditions. Real-time data and pressure variations also allow for prompt responses to any abnormalities.

• Efficiency: By monitoring pressure, equipment and systems are operating within the specified pressure ranges. This prevents unnecessary strain on machinery to optimize processes for maximum efficiency.

• Quality Control: Consistent pressure levels in manufacturing processes maintain stable production quality, reduce waste and enhance overall efficiency.

• Predictive Maintenance: Pressure transmitters assist in predicting potential equipment failures or issues, facilitating proactive maintenance to prevent costly downtimes.

• Compliance: Many industrial operations are subject to regulations regarding pressure levels. Pressure transmitters help in ensuring compliance with these standards.

Pressure Transmitters & Transducers Application 

• Oil & Gas

• Chemical Industry: petroleum, coal mine, Daily chemical industry

• Pulp and Paper

• Electricity

• New Energy: lithium battery, photovoltaic

• Food & Beverage Manufacturing

• Pharmaceuticals

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