I would like to ask everyone about using differential pressure transmitters to measure flow rate
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There is a differential pressure transmitter on site to measure the flow rate through the orifice plate; I set the air conditioning system to zero, and the measured current is 4 milliamps. Why then does the control panel still show a flow rate of over 2000?
Check the power distribution isolator; measure the output from it to see if it is 4mA. If not, then the output of the power distribution isolator must be drifting!
What is the range? Does the DCS provide low-flow cutoff?
I guess the cable tray where you placed it together with the power cables is causing interference
The key is what your range is; if the range is large, such drift is normal, and it can be addressed by adjusting the DCS zero point.
Verify that the output current at both the site and the cabinet room is 4 mA; taking zero drift into account, a low-flow cut-off value will suffice. . .
Check whether the range of the control panel matches that of the gauge
Measure the voltage in the control room to see if it is 4mA; if so, there is likely a problem with the isolation barrier
Check the safety barrier output current; what is the DCS range?
Several possibilities: 1. First, check whether the range setting at the site is consistent with that in the DCS. 2. Check whether small-signal rejection is enabled (whether the output cutoff function in the intelligent transmitter and the small-signal rejection function in the DCS are active). Either party can be put into operation.) 3. Signal disturbance 4. Leakage in the pressure lead pipe (negative pressure side)
It is also necessary to consider issues such as zero drift in the transmission stage and sensors, as well as changes in line resistance