Abnormal phenomena occurring with the ROSEMOENT radar level gauge
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Here is a phenomenon that has recently occurred with a ROSEMOUNT radar level gauge, which I cannot understand: 1. This phenomenon happens roughly once every three months, where the output signal fluctuates within the 0–20mA range; it persists for 6–8 hours before returning to normal. Additionally, even when the 24V power supply is disconnected, it takes the same amount of time for the gauge to recover. During this period, no numbers are displayed on the meter; instead, several black 8s are shown. 2. Before normal display, the operating voltage is 21.4 V; after normal operation, it is 20.2 V. The voltages in the other circuits were all above 23 V. 3. The signal cable was replaced, but the fault persisted. 4. Power the instrument directly using a process calibrator; the display is correct and there is no delay. 5. Signals sent from the field using a process calibrator to the DCS are accurate and do not fluctuate.
Based on what you’ve described, I think it’s likely a problem with the power supply or the cables. I’m not sure whether by replacing the cables you mean using temporary cables or installing new cables in the existing cable trays. It’s best to run a temporary wire to rule out any other interference in the cable tray. Here are a few suggestions that you can try. 1. Ground the signal cable from the cabinet side on one side only. 2. Use the existing cables, power it from the cabinet side with a handheld power supply, and investigate the power supply issues. Or use a 220V to 24V power switch directly. There’s one thing I don’t understand either: you say it happens once every three months, and I can’t figure out why.
Given this phenomenon, it might be a problem with the circuit board, resulting in a black screen; it could also be part of the restart and self-check process. For new devices, you can contact the manufacturer for a replacement, while for older devices, try replacing the circuit board
Are these 8 hours the 8 hours during the day? Is there any pattern, are there any activities going on around here?
Thank you all for your replies. 1. The three months I mentioned are approximate; it was only one month for the last time； 2. The signal cable has been replaced with another buried one ； 3. It takes 8 hours to recover, regardless of whether it’s day or night; whenever there is a power outage or the screen goes black, 8 hours are required for everything to return to normal.
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When powered by a signal generator, and after power is cut off and then restored, it shouldn’t be able to function properly right away?
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Is there a problem with the power board? Is it solved? If so, please share
This is a radar waveform issue; you need to use computer radar debugging software to examine the fundamental wave and reflected waves, then analyze the dynamic waveform and make adjustments – that should resolve it