I am totally new in this field. I want to use a 5 V / TTL signal from a National Instrument to switch on/off a Red lion PXU series temperature controller. But this controller required a dry contact input or a prox sensor with NPN open collector. What does it mean?

How will the circuit look like?

Thank you in advance!


It means you need to pull down the input to instrument ground with a transistor or switch.

Read the specifications to determine what voltage it pulls up to, or just add an NPN transistor and base resistor (eg. 2N4401/4.7K) to your logic circuit. Grounds must be common.


simulate this circuit – Schematic created using CircuitLab

You can probably use a transistor or MOSFET-output optoisolator rather than a transistor if you need isolation, but you may need a driver for the optoisolator LED.


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