What is the difference in the internal structure of gauge pressure meters and absolute pressure meters?
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What is the difference in the internal structure of gauge pressure meters and absolute pressure meters? Are transmitters divided into gauge pressure transmitters and absolute pressure transmitters?
The difference between a gauge pressure gauge and an absolute pressure gauge is that the absolute pressure gauge has a vacuum reference chamber; it shows the atmospheric pressure when exposed to the atmosphere, while the gauge pressure gauge shows zero in such conditions. Transmitters also include gauge pressure transmitters and absolute pressure transmitters.
A gauge pressure meter is a pressure gauge that uses atmospheric pressure as a reference; its pressure-sensing element responds directly to the process pressure and displays the gauge pressure. A gauge pressure meter, on the other hand, is a pressure-sensing element based on vacuum. The most direct method is to disassemble these two pressure gauges separately and examine them. Based on the characteristics of the process pressure they measure, pressure transmitters can be classified into gauge pressure transmitters, absolute pressure transmitters, and differential pressure transmitters.
The 4‑20mA signal from a gauge pressure transmitter corresponds only to the gauge pressure value A; to determine the absolute pressure, subtract the local atmospheric pressure from this gauge pressure value (calculate it manually)； The 4‑20mA signal from the gauge pressure transmitter corresponds only to the gauge pressure value G, that is, the local atmospheric pressure at that time. Generally, when measuring process gases with an absolute pressure of less than 20 KPaA, an absolute pressure transmitter is used; if it is the pressure discharged by a fan, a differential pressure or gauge pressure transmitter will suffice. The negative chamber of the gauge pressure transmitter is evacuated during manufacturing; of course, an absolute vacuum of 0 KPaA cannot be achieved – it’s around ten or so PaA, more or less. When calibrating the gauge, you need to calculate the current value corresponding to 2KPaA (which may vary among different manufacturers; for example, it could be 4.2mA), and then use that value for calibration. In other words, the 4mA point is calibrated \"virtually\", as there is no standard source for absolute vacuum. @jiaguoyun