When the four-wire level gauge is powered on, there is voltage between the signal lines and ground
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Here’s the situation: for the company’s four-wire level gauges, two of the wires carry 24V power, while the other two carry signals. Now let’s disconnect both ends of the signal wire; whenever the 24V power supply is turned on, there is a voltage of 3-4V between the signal wire and ground. What’s causing this? Is there anyone who can answer this? . .
It’s probably because the circuit is grounded; check the insulation against ground and against the casing one by one
It’s abnormal when there is no voltage; the + terminal will definitely have voltage, and the – terminal may also have it, as its potential isn’t necessarily the same as that of the negative terminal of the power supply.
There is voltage on the line, so such measurements don’t tell us anything...
No, there are 4 cores in total; 2 of them are used for power supply, while the other 2 are used for signals； Now disconnect both ends of the 2-core cable used for signaling ； When the 2 pins used as a power supply are energized, the other 2 pins have a voltage with respect to ground, of about 3-4V. The cable is RVVP with 4 cores of 1.5mm2 ； Upon measurement, the cable insulation is fine ； Moreover, the shield wire is properly grounded. I really can’t figure out what’s going on no matter how hard I think about it.
No, there are 4 cores in total; 2 of them are used for power supply, while the other 2 are used for signals； Now disconnect both ends of the 2-core cable used for signaling ； When the 2 pins used as a power supply are energized, the other 2 pins have a voltage with respect to ground, of about 3-4V. The cable is RVVP with 4 cores of 1.5mm2 ； Upon measurement, the cable insulation is fine ； Moreover, the shield wire is properly grounded. I really can’t figure out what’s going on no matter how hard I think about it.
It’s probably induced electricity; if another power cable is connected, this issue might not occur. If it’s allowed, you can try that approach.
As long as the communication is normal and the measurements are accurate, that’s fine
Isn’t this abnormal? For a 4-20mA signal, there is impedance in the circuit; doesn’t that result in a voltage?
If it is a stranded wire with a shielding layer, grounding it properly will solve the problem!