Can I use five analog differential signals in usb 6008?

[Pylzy]

Hi!

I have the USB-6008 with one temperature sensor and two potentiometers (and one counter and digital input is also beign used).

I've got only one analog +- slot left but I still need to connect voltage and current signals from a power supply. Is it possible to have them both connected somehow to the last +- slot?

If it's not possible which harware would you recommend instead of the 6008?

[SnowMule · Accepted solution]

6211's about the next best step up that gets you more AI's. 

Alternatively, you could just put a 2nd 6008 in the system.... certainly cheaper than a 621x board.

[Pylzy]

BTW the temperature sensor and potentiometers use the same power supply. Would it be posible to connect all of the ground wires to the same pin?

Then I would have plenty of free space in the box since the grounds would be in the same pin.

[SnowMule]

Depends on the signals and ranges you want to measure.

Configuring an input as RSE locks the DAQ at 10V range.  Using differential, you get 8 ranges from 1 to 20 volts. 

It's perfectly acceptable to take a 3-terminal device (power, signal, ground) and split the ground to both the negative diff input and ground to use those other ranges on the DAQ.

If 10V is adequate and the sensor's output is referenced to ground, use the RSE and save yourself the inputs.

[Pylzy]

I think I need the differential range. When I choose the analog inputs with daq assistant it doesn't allow me to choose which ground/- it uses.

Let's say I want to connect three + signals to AI0, AI4 and AI1. Then the ground reference would be connected AI5. Could this be done with labview? I can't find any manual setting for the ports used.

[SnowMule]

Differential uses 0/4, 1/5, 2/6, and 3/7.  Can't reconfigure those pairs, but you can configure whether it's one differential measurement or two independent RSE measurements.

If you want to mix-and-match, say use two differential and (up to) four RSE, you'd have to put the diff pairs on 0/4 and 1/5, leaving you channels 2, 3, 6, and 7 for the single-ended measurements.

Think of it like a DMM... If you hook the black lead to the ground of the power supply on your bench, then probe various points with the red lead leaving the black lead in place, you're making RSE measurements.

But if you take the black and red lead, then poke a particular component, you're making a differential measurement.

Diff is more accurate and allows greater measurement flexibility on the DAQ at the expense of only having four "multimeters".

To get 5 inputs, you could do 3 differential pairs and use the last two channels as single-ended. 

[Pylzy]

Thanks! 🙂 I got everything in working condition.