How to connect 40 differential analog input signals to USB-6255 using SCB-68 (2 set).

[SLamazon]

Hello

I have USB-6255 DAQ which required external SCB-68 for instrumentation.

I have 8 SCB-68 devices but at a time i can connect only 2 SCB-68 device to USB-6255.

In my application, i need to connect 40 differential analog input channels and 40 single ended analog input to effectively monitor 40 power rails of embedded system (at least 30 power rails)

I am using SCI-Lab script to gather data from the DAQ. So far i have hooked up 8 power rails (i.e.. 8 differential channel + 8 single ended channel) and that is working fine.

From SCB-68 quick reference label, it has 15 analog input channels. In my connection, each power rails it consume 3 channels (i.e.. 2 for differential + 1 for single ended), so i can effectively connect 5 power rails using 1 SCB-68.

All other channels are digital and PFI which are useless for my application.

So even i use 2 SCB-68, i can connect only 10 power rails. I need to hook up other 30 power rails (at least 20 more).

Datasheet of USB-6255 says it is 80 channels  DAQ. So, how should i set DAQ or SCB-68 for all analog input channel. i do not require to connect any digital input.

May i have your support please?

Your kind help will be really appreciated.

SL-Amazon

[FoxSquirrel]

Hello SLamazon,

If you are using the USB-6255 that is mass terminated, you are only going to be able to use two SCB-68s at a time.  However, these two SCB-68s will give you access to all 80 of the Analog inputs.  The two pinouts you are looking at in the attached PDFs are references for the NI 7811R/7831R device.  The pinout you want to look at is the one located here.

With regards to how you connect the devices, since you only have 80 analog inputs to work with, if you are wiring the differentials up to two analog inputs each, you will only be able to connect 30 differential and 20 single ended (or some combination of the two that take up 80 analog inputs.)

I hope this helps!