USB-231 noise on additional channels

[BrianC]

We have a USB-231 that has a single input attached to channel 0 in SE mode. The input is outputting 0-5V, so the reading is somewhere from 32000-48000, normally (since this device supports -10 to +10V).

We notice that when trying to read the other 7 channels, there seems to be noise on the next 3 channels that elevate the reading above 0V pretty significantly. We are going to test connecting those empty channels to ground, but I was wondering if there is a configuration with pull-down resistors like on some of the other Digital I/O devices? If not, I suspect manually connecting these channels to ground is the way to go to ensure they get the 0V expected.

Also, is it possible to force the configuration to the expected voltage range when using cbAIn. The board specifies -10V to +10V, but is that a maximum suggesting and we can set it to 0 to +5V instead?

[Fausto]

Hello @BrianC.

In your software application, enable only those analog input channels with an external signal connection.  Additionally, as you stated, short all unused analog input channels to AGND.  The analog input voltage range is +/-10 V only.

Regards,

Fausto