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Concept of pressure transmitters: Transmitters evolved from sensors; they are any sensors that are capable of outputting standard signals. A standard signal is one whose form and quantitative range of a physical quantity comply with international standards. Due to the advantages of DC signals, such as being unaffected by inductance, capacitance, and the characteristics of the load in the circuit, as well as having no phase shift issue, the International Electrotechnical Commission (IEC) has designated current signals of 4mA–20mA (DC) and voltage signals of 1V–5V (DC) as the unified standards for analog signals in process control systems. Working principle of pressure transmitters The working principle of pressure transmitters is to convert the weak, non-electrical pressure signal collected by the sensor – that is, the pressure variable – into a standardized signal that can be transmitted. This signal is also amplified so that it can be used by secondary instruments such as indicator alarms, recorders, and regulators for measurement, indication, and process control. The converted electrical signal has a certain continuous functional relationship with the pressure variable (usually a linear function). A pressure transmitter mainly consists of three parts: a sensitive element, a sensing element, and a measurement conversion circuit. Pressure variables include positive and negative gauge pressure, differential pressure, and absolute pressure. Pressure transmitters can be divided into two types based on their pressure measurement range: ordinary pressure transmitters with a range of 0.001–20 MPa, and micro-differential pressure transmitters with a range of 0–1.5 kPa. Classification of pressure transmitters: The classification of pressure transmitters is primarily aimed at better meeting customer requirements; they have different structures and use different diaphragm boxes. A pressure transmitter, also known as a general-purpose gauge pressure transmitter, has one side connected to the atmosphere and the other side connected to the pressure to be measured. Used for measuring pressure in pipes, boilers, etc. A differential pressure transmitter is connected to different pressures on each side; it measures the level of liquid based on the pressure difference, and can also be used in conjunction with orifice plates to measure pipeline flow rates. An absolute pressure transmitter has a vacuum on one side, and the pressure on the other side is the absolute pressure; it is suitable for applications requiring absolute pressure. The differential pressure transmitter uses a 2E diaphragm cell (0.0–1.5 KPA) to improve the accuracy of measuring low pressures. High-static-pressure differential pressure transmitters use high-static-pressure diaphragms. By static pressure is meant that when the pressures on both sides of the pressure transmitter are equal, its output current should be 4.00 MA. However, in ordinary differential pressure transmitters, it becomes difficult to maintain an output of 4.00 MA when the pressures on both sides increase to over 25 MPa. Therefore, high-pressure differential pressure transmitters are commonly used in applications involving flow and level measurement under high pressure conditions. Application scope of pressure transmitters: 1. Oil and gas/petroleum chemicals/chemical industry ； 2. Power/urban gas/other corporate operations: locations that require high stability and high-precision measurements, etc ； 3. Pulp and Papermaking ； 4. Steel/Non-ferrous metals/Ceramics ； 5. Machinery/Shipbuilding. Functions of pressure transmitters: 1. The function of a transmitter is to detect process parameters and transmit the measured values in a specific signal format, so that they can be displayed and adjusted. 2. Its role in automatic detection and control systems is to convert various process parameters such as temperature, pressure, flow rate, liquid level, composition, and other physical quantities into standardized signals, which are then sent to controllers and indicator recorders for regulation, indication, and recording. Technical development of pressure transmitters: Pressure and differential pressure transmitters are an important category of process variable transmitters with a wide range of applications. In addition to measuring pressure and differential pressure, they can also be used to measure other parameters such as flow rate, level, and specific gravity. In a 5000 t/d cement production line, pressure transmitters must be installed at key points throughout the process flow, such as at the kiln inlet and outlet, at the top and bottom of each preheater stage, in various air ducts, and in the different chambers of the cooler, in order to monitor the proper operation of the process. According to statistics, a new dry-process cement production line requires approximately 80 pressure transmitters in total. After reading all this, do you now understand transmitters?