Will this have an impact on instrument measurements?
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There is a two-wire level transmitter that is not displaying any output. Upon inspection, it was found that the system has 24V+ connected to ground, with a resistance of 200–500Ω between it and ground. Since the site is far from the control room and the environment is harsh, giving up on checking the wiring, the + and - terminals on each side were swapped; the wire that was previously grounded was used as the 24V- terminal, and the transmitter was able to display its output. Will this wiring method affect the proper operation of the transmitter?
You’re right about geopotential; in my personal understanding, it refers to a potential difference, and in engineering applications it is commonly referred to as voltage. Regarding the 24V power supply you mentioned, in fact it makes no difference whether it is grounded or not. With the negative terminal as the reference point, the potential difference between the positive and negative terminals is 24V; with the positive terminal as the reference point, the potential difference between the negative and positive terminals is -24V. If you ground the positive terminal, the two become connected and are at the same potential, so the potential difference (the potential of the positive terminal relative to ground) is naturally zero. And the potential difference between the negative terminal and ground is naturally the potential difference between the negative terminal and the positive terminal, which is -24V. Simply put, for a 24V power supply, use a DC voltmeter: connect the black probe to the negative terminal of the power supply, resulting in 24V; connect the black probe to the positive terminal, resulting in -24V.
It’s best to check the junction box and control room to see if there are any spare wires. It does display correctly, but does it have any impact on the indicated values?
The indicated values were basically the same at that time; the concern was potential problems in the future, as well as whether it might have an impact on the safety of the instruments
It should work properly; this isn’t necessarily the case for remote transmission. Check whether the display matches the output, and also see if it corresponds on the side of the secondary meter
It works for now, but there may be potential issues in the future. The resistance from the negative terminal to ground is 200–500Ω; such a high resistance, combined with the resistance of the load itself, may result in problems with accurate signal transmission. Moreover, this ground resistance is arbitrary and can vary significantly depending on weather conditions. There is also a possibility of damaging the transmitter or causing the upstream voltage switch to trip.
It shows that it is available, but can it ensure that the circuit current remains unaffected? Does the header display correspond to the loop current?