10-04-2012 09:40 AM
OK so this is a really simple test, however it seem to just go on and on.
I am using an NiDaq and a 9205 card.
I have 20 chanels that have 5v on them.
I am reading the voltages using RES with a common ground. The test is to take 1 sample per second and see when one of the cables is disconnected.
Expected results should be 5v on all the channels and 0v on the channels that are disconected.
Well that is not the case, i am getting the correct voltage on the chanels i have the 5 volts connected to but redom number from -10 to +10v on all the others.
10-04-2012 04:14 PM
Open inputs will float around randomly as you observed. Search the forum for "ghosting". You need a pull down resistor from the input to ground, try 1K to 10Kohms.
-AK2DM