d123
Advanced Member level 5
Hi,
This is a question about hypothetically measuring a cable for continuity that is too long for a DMMs test leads, maybe 3m long or 1km long, whatever you prefer.
Regarding a long-distance continuity tester/function that can operate with a cabled signal over one wire but with no return cable between Tx board and Rx board (I know/think such devices don't exist), why can't they work if both circuit halves (send end and receive end) use the same voltage batteries and voltages, the same parts, and have a near-identical layout on both boards, especially the power and return paths?
Wouldn't 5V look like 5V and 0V like 0V to both boards, so the signal would arrive from circuit 1 to circuit 2 looking and feeling like ~5V to circuit 2 input pin?
Just wanted to check what the reasons for not doing this are:
Searched a few times for online information but nothing useful good has come up, I wanted to know the contras of such a set-up.
I know grounds need to be connected together between different boards, and have measured horribly wrong signals on and between two boards where they weren't, but I just can't see why identical, isolated circuits would not function correctly in this respect.
Any explanation affirming or refuting the reliability for this two PCBs and two grounds block diagram as in the image, much appreciated.
This is a question about hypothetically measuring a cable for continuity that is too long for a DMMs test leads, maybe 3m long or 1km long, whatever you prefer.
Regarding a long-distance continuity tester/function that can operate with a cabled signal over one wire but with no return cable between Tx board and Rx board (I know/think such devices don't exist), why can't they work if both circuit halves (send end and receive end) use the same voltage batteries and voltages, the same parts, and have a near-identical layout on both boards, especially the power and return paths?
Wouldn't 5V look like 5V and 0V like 0V to both boards, so the signal would arrive from circuit 1 to circuit 2 looking and feeling like ~5V to circuit 2 input pin?
Just wanted to check what the reasons for not doing this are:
Searched a few times for online information but nothing useful good has come up, I wanted to know the contras of such a set-up.
I know grounds need to be connected together between different boards, and have measured horribly wrong signals on and between two boards where they weren't, but I just can't see why identical, isolated circuits would not function correctly in this respect.
Any explanation affirming or refuting the reliability for this two PCBs and two grounds block diagram as in the image, much appreciated.