It’s still an issue with the instrument wiring, thanks
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I’m sorry, gentlemen – I didn’t phrase my previous question clearly enough. What I actually wanted to ask is whether there are any rules regarding the order in which the wires from two different instruments should be connected So, it works either in forward or reverse polarity?
In a two-wire system, there is a positive and a negative wire; the two wires in your cable should be colored differently. One color should be designated as the positive terminal, and all the wires corresponding to the positive terminal should have the same color
There should be; it seems that alarm instruments such as pressure alarm switches and level alarm switches can, to some extent, handle polarity issues.
It needs to be divided into positive and negative values; for digital signals, it is generally categorized as normally open or normally closed, with further distinctions as well
It comes in positive and negative versions; the 24V power supply is DC. Also, digital signals are divided into NC and NO, so it’s important to pay attention to that.
First, it is necessary to determine what type of two-wire instrument it is. If it is a 4–20 MA current signal, then the positive and negative poles must be separated, as the system needs to supply power to the instrument； If it is a digital dry contact, the signal line going to the field has no positive or negative distinction; however, care must be taken to connect it in normally open or normally closed configuration! :handshake
Switch-type contacts do not require distinction between positive and negative; the others generally do
Analog signals are polarized, while dry contacts are non-polarized.
Digital signals are not distinguished; all instrument transmission signals are categorized
Analog signals have positive and negative values, while digital signals do not! ! ! :victory:
There is no such instrument, because in a two-wire connection the purpose is first and foremost to supply power, and there must be a distinction between positive and negative； At the same time, as a signal return, there must also be a distinction between positive and negative; therefore, it is necessary to identify which is positive and which is negative when making the connections.
Two-wire instruments all have positive and negative poles, as it is direct current, and direct current inherently has positive and negative sides; unless it is a switch-type instrument that does not have such poles. But even in the case of switch-type instruments, the circuit that provides power on the other side also has positive and negative poles