In this series, we will introduce the pressure transmitters commonly used in our working conditions.

　　1. Brief description:
Pressure transmitters generally refer to pressure transmitters and differential pressure transmitters, mainly composed of pressure sensing elements, measurement circuits, and process connections. They can convert the received pressure signals from gases, liquids, etc., into standard current and voltage signals (4~20mADC) for secondary instruments such as indicating alarms, recorders, and regulators for measurement, indication, and process adjustment. Pressure transmitters can be divided into general pressure transmitters (-100Pa to 120MPa) and micro differential pressure transmitters (0.1 to 1.5kPa) based on their measurement range.
　　2. Main functions:
Transmit pressure signals to electronic devices, which then display the pressure on a computer. The principle is roughly as follows:
For example, converting the mechanical signal of water pressure into an electronic signal such as voltage or current (usually 0-5V or 4-20mA), where pressure and voltage or current are linearly related, generally in direct proportion, so the voltage or current output from the transmitter increases with increasing pressure.
　　3. Product types:
By range: micro pressure transmitters, pressure transmitters
By measurement method: differential pressure transmitters, pressure transmitters
By measurement requirements: absolute pressure transmitters, gauge pressure transmitters, relative gauge pressure transmitters.
1. Definition
Absolute pressure = gauge pressure + atmospheric pressure
Gauge pressure: refers to ordinary pressure transmitters used for conventional pressure detection.
Absolute pressure: generally used to measure conditions that may produce negative pressure. An absolute pressure gauge should display 102Kpa when not in use, which is the local atmospheric pressure.
Differential pressure: generally used for flow and liquid level detection, it is the difference between two pressures.
2. Differences:
A pressure transmitter, also known as a general gauge pressure transmitter, has one side open to the atmosphere and the other side connected to the measured pressure. It is used for measuring pressure in pipelines, boilers, etc. A pressure transmitter has only one pressure tap, measuring pure pressure;
A differential pressure transmitter has two pressure taps, measuring the pressure difference. If a differential pressure transmitter is connected only to the positive or negative diaphragm chamber, it is equivalent to measuring with a pressure transmitter. The differential pressure transmitter connects different pressures on both sides to measure the height of liquid levels and, in conjunction with orifice plates, to measure pipeline flow.
An absolute pressure transmitter has one side under vacuum, and the pressure on the other side is the absolute pressure, suitable for absolute pressure applications.
Micro differential pressure transmitters use 2E diaphragm boxes (0.0-1.5KPA) to improve the accuracy of measuring small pressures.
High static pressure differential pressure transmitters use high static pressure diaphragm boxes. The so-called static pressure means that when the pressures on both sides of the pressure transmitter are equal, its output current should be 4.00MA. However, ordinary differential pressure transmitters find it difficult to maintain an output of 4.00MA when both sides' pressures increase to above 25MPA. Therefore, high static pressure differential pressure transmitters are often used in flow and liquid level measurements where the pressure is relatively high.
　　4. Besides measuring pressure, what else can pressure transmitters measure?
1. Liquid level
Pressure transmitters and differential pressure transmitters, by name, measure pressure and differential pressure (the difference between two pressures), but they can indirectly measure many other quantities. In addition to measuring pressure, they can also measure the liquid level within equipment. When measuring the liquid level in a normal pressure container, only one pressure transmitter is needed. When measuring the liquid level in a pressurized container, two pressure/differential pressure transmitters can be considered, one for measuring the lower limit and one for the upper limit. Their output signals can be subtracted to determine the liquid level.
2. Density
Under conditions where the liquid level and pressure value in the container remain unchanged, it can also be used to measure the density of the medium.
3. Flow
The measurement range of pressure transmitters can be very wide, starting from absolute pressure 0 to over one hundred MPa (under normal conditions). In addition to measuring the differential pressure between two measured pressures, differential pressure transmitters can also be used in conjunction with various throttling elements to measure the flow of fluid mediums.