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Reading Contact Closure status

DaveO Jul 30, 2014 03:42 AM

I need to monitor the status of a contact closure that occurs when a pump is turned on (ie contact is closed when pump is on). Is the best solution to put one wire in 5V and the other wire into a SE port to measure the voltage? The pump can remain on for hours and I want determine when it is on and off every 60 second scan interval.

Thanks
Dave O

Sam Jul 31, 2014 05:01 PM

That is one way of doing it. You can also run the return line back to a control port and using the PortGet() instruction. Either would work fine.

You could also put a pair of resistors in parallel with your pump switch to determine that the line has not been damaged / cut. For example, when pump is off SE port reading will be 2.5V and when pump is on SE port reading will be 5V. Put one high valued resistor in parallel with the switch in/out at the pump. Put another resistor of equal value between SE and ground. Now you will have 3 states you can monitor 0 = FAULT, 2.5 = PUMP OFF, 5 = PUMP ON.

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