measuring output state on USB-6525

[NJGW]

Hi,  is it possible to verify the state of the SSRs in a USB-6525 using a multimeter.  I connected a meter to measure the resistance across the output connections  P0.0A and P0.0B.  I wanted to use the self-test routines to verify that the SSRs were closing.  As expected there was an open circuit when the TTL was 0,  but the circuit did not appear to close when I changed the TTL to 1.  Do I need to connect a power source and load to be able to see the SSRs closing?  Isn't that what a multimeter is?

Thanks,  Nick

[Wayne.C · Accepted solution]

Nick,

Multimeter will not provide the voltage source and load you need.  See this link.  http://digital.ni.com/public.nsf/allkb/B0FF01B2AFFA52FC862573A2005A9570

[Now_With_Underscores]

Hey Nick,

As the KB Centerbolt posted explains, we need an external power source to provide power to the device under test.  The relay module does not provide any power; it simply switches on or off.  The DMM you're using provides a small bias voltage in order to measure the response current, which is then divided out (IR=V) to find the resistance.  The amount of power sourced from the DMM is very very small and is not enough to overcome the internal effects of the semiconductor circuitry.