Labview RSE measurement USB 6225

[´MikeSv]

Hello everyone.

I recently got a USB-6225 and wanted to test it with Labview.

I took a 5V signal and connected the + to a0 and - to AIGND. Then i took a second cable from the + side and connected it to a1.

But now something strange is going on.

If i measure a0 and a1, 5 Volt is shown... If I remove a1, the channel still shows 5V.

First when I remove a0, both channels are zero....

I don't know what is happening.... When I measure with a voltmeter it seems fine....

Greatful for any advice,

best regards,

Michael

[GerdW]

Hi Michael,

the 6225 uses a MUX for all AI channels, so you will see "ghosting" for unwired inputs!

To avoid ghosting you may use pullup/pulldown resistors - which could interfere with your measurement setup. Or use the approach in the linked AppNote…