1769-IQ16 Sink or Source

I need to make a drawing for wiring a 1769-IQ16 module. I have a drawing from AB that shows it will do sink or source.

What is the common u.s. method? What's best?

Bump

Depends on whether you are using PNP (sink) or NPN (source) sensors.

If the minus side of the sensor's DC power supply is grounded to the frame then use 'sourcing' devices (module wired as 'sinking'). If the plus side is grounded then use 'sinking' devices (module wired as 'sourcing'). If neither then it is your choice.

This is to prevent a shorted-to-frame wire giving a false ON condition.

I think sinking inputs and sourcing outputs are the most common US configuration, and this is my preference. A lot of the European and Asian machinery we get has the opposite.

One argument in favor of sinking inputs has to do with the likelihood of a short circuit causing a false signal to your input. With sourcing inputs, you're pulling the input to common (24v-) to activate it. If your machine has the 24v- tied to ground, and the machine frame is also grounded, it creates a lot of surfaces that could potentially short against the signal wire and activate the input. However, in practice it's probably much more likely that the wires inside a frequently-flexing sensor cable would abrade and short together (seen it happen many times) and in that case the sinking/sourcing setup wouldn't make a difference.

bernie_carlton said:

If the plus side is grounded then use 'sinking'.

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I often see the minus side grounded but never the + side. I think I've heard of a positive ground in some automotive applications. Where is this done in an industrial setting and for what reason?