The PLC inputs should be (and are) positive.
It may be that the schematic is drawn the wrong way round - I've relied on the +,- and ~ printed on the rectifier hardware and they work OK...
I am trying to design a circuit with multiple full wave bridge rectifiers (with smoothing) to act as liquid level control.
I am using bridge rectifiers as I need AC to detect liquid level to avoid electrolysis in the liquid, but a 'DC' signal to a PLC.
A single bridge rectifier works very...
