11-20-2014 02:49 PM
We are getting analog voltage changes in Labview on several different inputs (not found with multimeter). It happens when we activate the NI 9481 relay module with a 24V DC signal to power a solenoid. Don't understand why this is happens or why it shows on three different inputs in LabVIEW but not when testing the points with a meter.
11-20-2014 06:08 PM
11-21-2014 03:43 AM
Some more information is needed!
How does your setup looks like? Cabling?
How do you measure your voltage? (Can you capture some voltages in high sampling mode while switching?)
I assume an EMC issue.... however my crystal ball unforseeable drops from my desk 😄
11-21-2014 01:20 PM
The 24V is only sent from power supply through relay to solenoid. The inputs are all 4-20 mA signals converted to 1-5V by a 250 ohm resistor across the ckt. The inputs come from a LVDT, extensometer, and a load cell. We had to convert the signals to make them readable by the 9381 module that we already had.
11-21-2014 02:24 PM
That picture is of little help, since the devices will report what they measure, wether it is the voltage of interest or not 😉
To find the root cause of that effect, you 'just' have to follow the current. However current and to note _fast changing current_ can go funny, not always so obvious ways.
That's why I asked for details of the setup, and every wire counts 😉
(and ground is a con...... see sig)
And a as fast as possible sampled voltage channel while a switch is actvated (say 20ms) would help too.