Simple switch circuit wiring advice

[samfau2]

Hello,

I have an NI PXIe-6361 device and am trying to wire up a simple circuit with a switch so that when the switch closes, the DAQ reads a voltage and when the switch is open the DAQ reads no voltage.

Ideally I would like to provide the voltage from the 6361 itself if that is possible. My question is, how would i wire up such a circuit to the ports on the NI 6361. I have been told that I will need to connect a ground to prevent the readings from floating, is this just a case of connected to the AI GND terminal? This is what I have in mind but my electronics knowledge is very limited!....

Many thanks for your help.

Sam

[crossrulz]

You will want a pull-down resistor across your analog input (after the switch to ground).  A 1MOhm should do just fine.  The point here is that you can't just leave the input completely floating.

[samfau2]

Thanks crossrulz that's helpful. Could you clarify where exactly the resistor would be and how to connect it? I will try to find something online and confirm it is what you mean. Cheers, Sam.

[samfau2]

Will something like this suffice?

http://www.maplin.co.uk/p/metal-film-06w-1m-ohm-resistor-m1m