I would like to ask what causes the incorrect reading on the V-type flow meter
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Today was my first time conducting a test drive. On the DCS, it was found that the V-type flow meter used to measure the exhaust gas flow rate was giving abnormal readings – the values were much higher than the actual flow rate. When a 0% signal was sent to this meter using a process calibrator, the DCS showed a flow rate of zero; when a 25% signal was sent, the DCS displayed a value of over 30%. With a 50% signal, the DCS showed around 70%, and when a full signal was applied, the DCS displayed the normal value of 100%. There were no issues with the zero point or the range of the differential signal, nor were there any problems with the signal transmitted to the I/O station. Our plant uses the Yokogawa CS3000 system. I would like to ask the experts what the cause is and how it should be resolved.
1. The field instruments do not correspond to the range specified in the DCS in the control room. 2. The shielding cables of the instruments are not grounded. 3. There is significant vibration at the installation sites in the field. 4. The measurement range of the instruments was set too low
It is obvious that the range setting of the DCS is too large, and it does not match the range of the transmitter.
Reply to 4#: For the three hairs on the head, send a signal back to the tester; if taking a square root within the system, 0 corresponds to 0, and 25% corresponds to 50%. . . ?
You’d better connect a multimeter to it. It’s probably your “process calibrator” that’s inaccurate!
Reply to 5# hzyhyb: Check the DCS range first! When performing loop testing with a signal generator, check whether the current is correct.
The guy on the 4th floor might be wrong; the range is correct. I analyze: 1. Was taking the square root not considered, 2. Has the differential pressure transmitter been calibrated? How about linear? 3. Is it necessary to calibrate the measuring instruments? 4. Check if there are any other reasons on site. The possibility of wire loosening is low; vibration has little effect on cone tube flow meters, but it has a significant impact on vortex flow meters, electromagnetic flow meters, and mass flow meters.