The result measured by the differential pressure transmitter is the pressure difference, that is, P=F/S. When the temperature changes, although the volume of the oil product expands or shrinks, and the actual liquid level increases or decreases, the detected pressure always remains the same. If the user needs to display the actual liquid level, it can also be solved by introducing medium temperature compensation.
Two-wire output wiring is an advanced output method in the current analog serial port, with 6 major advantages:
1. The micro-differential pressure transmitter is not easily affected by parasitic thermocouples and resistance voltage drop and temperature drift along the wire, especially for the air differential pressure transmitter. The cheap and thinner twisted-pair wires can be used.
2. When the output resistance of the current source of the differential pressure transmitter is large enough, the voltage induced into the wire loop through the magnetic field coupling will not have a significant impact. Because the current caused by the interference source is extremely small, the use of twisted-pair wires can generally reduce the interference.
3. The capacitive interference of the differential pressure transmitter will cause the error related to the receiver resistance. For the 4-20mA two-wire loop, the receiver resistance of the differential pressure transmitter is usually 250Ω (sampling Uout=1～5V) . This resistance is too small to produce a significant error, so the allowable wire length is longer and farther than that of a voltage telemetry system.
4. Each single display or recording device of the differential pressure transmitter can be switched between different channels with unequal wire lengths, and there will be no difference in accuracy due to unequal wire lengths;
5. The micro-differential pressure transmitter uses 4mA for zero level, which makes it very convenient to judge whether the transmission line is open or the sensor is damaged (0mA state).
6. The micro-differential pressure transmitter is easy to add surge protection and lightning protection devices at the two-wire output port, which is beneficial to safety, lightning protection and explosion protection.
LEFOO develops and manufactures reliable, high-quality standard pressure control and temperature control equipment, and provides innovative solutions and components. Our certified pump engineers can create the right solutions to complete almost all hydraulic water supply plans. From water supply report analysis, detailed drawings and budget suggestions, prototypes. If you have any needs, please feel free to consult us.
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