Radar level gauge
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The field current of the Hawker radar level gauge does not match the DCS current, provided that the measurement ranges are the same. What is the reason for this?
Interference can intrude during the transmission of current signals, so it is necessary to implement anti-interference shielding measures.
Signal interference; it is recommended to add shielding facilities
Check the cables carefully; I’ve encountered this issue before as well. It turned out that one end of the cable inside the conduit was connected, and at that connection point the shielding layer came into contact with the metal casing, which caused the currents on both sides not to balance. The original poster might want to check whether this phenomenon exists as well
The range of the instrument may differ from the actual 4-20mA output; there might be differences between the settings in the PLC and those in the instrument. For example, if the range indicated on our radar’s nameplate is 20 meters (i.e., a height of 20 meters), then our output current of 20mA corresponds to a height of 19.5 meters. The 20mA value set by the PLC should also correspond to 19.5 meters, not 20 meters; the difference of 0.5 meters represents a blind zone, which is generally removed from the output value. This is for reference only – I’m not sure if it’s the same for Hawk devices
There is a problem with the shielding; check it carefully.
Check whether the instrument outputs level or distance; some level gauges are capable of outputting distance. Then check whether the instrument itself has a current calibration function; if it does, give it a try, and if not, contact the manufacturer. Personally, I think the chance that the cable has an impact is very small
Was it normal before or newly installed? If it’s a newly installed unit, the current output can be recalibrated