Problem with analog inputs on sbrio 9627

[Giuliano06]

Hey guys!!

I have a problem in my Single Board RIO 9627.
I am using 4 differential analog inputs (AI0, AI1, AI2 and AI3).
What happens is that when I place a sensor or even a button on one of the inputs, it affects all other inputs, raising each input voltage levels.
Can anyone tell me how to solve this in the hardware or software?

VI's are attached below.

Thank you!

[RavensFan]

This sounds more like a hardware question rather than a LabVIEW question.

What is connected to the other inputs when you put this sensor or button on the one input?

[Giuliano06]

I also believe it is hardware problem, but I put this question here to find it would have any way to eliminate this error through the software.
When I put the button on AI0 entry and nothing on the other inputs for example, the voltage on AI1 inputs, AI2 and AI3 increase,then,what once was around 0V (open channel) is replaced around 0.7V.
And it happens when I connect a button, accelerometer, or any other sensor on any input.

[RavensFan]

Since you say you have nothing wired to the other inputs, then you are probably seeing ghosting.

http://digital.ni.com/public.nsf/allkb/73CB0FB296814E2286256FFD00028DDF

You are seeing the remnants of the signal from AI0 because AI1 aren't able to discharge the instrumentation amplifier.  Technically, there any voltage could be valid on those analog input pins because they are at infinite resistance to the ground pin.

Try putting a jumper between AI1 and AGND and see what it looks like then.

If you don't have anything wired to those inputs, why do you even care what the program says when you try to read those inputs?

[Giuliano06]

RavensFan, I believe that what really happens is ghosting. I will try to link the solutions you sent me to see if it solves the problem. One of the following steps is impossible (Avoid Multiplexing), considering that to use more than one entry in the single board, the signals will be multiplexed.
Currently already put a jumper between AI1 and AGND, I have done this using the GND of the board and still the problem.

[Giuliano06]

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RavensFan escreveu:

Since you say you have nothing wired to the other inputs, then you are probably seeing ghosting.

http://digital.ni.com/public.nsf/allkb/73CB0FB296814E2286256FFD00028DDF

You are seeing the remnants of the signal from AI0 because AI1 aren't able to discharge the instrumentation amplifier.  Technically, there any voltage could be valid on those analog input pins because they are at infinite resistance to the ground pin.

Try putting a jumper between AI1 and AGND and see what it looks like then.

If you don't have anything wired to those inputs, why do you even care what the program says when you try to read those inputs?

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I care about the other entries because I will put a sensor in each entry in the future. Will be 4 sensors in total. When told that there was nothing plugged in the other entries is that right now I am using only one input for testing and development, and with it, I realized the problem.

[RavensFan]

I'm not concerned about you needing to wire sensors into the other ones in the future.  I'm asking why do you care about what a particular channel reads now when you know you don't have any valid input into that channel now.  The data is meaningless, so who cares what the data is at the moment.

I would short out the other inputs to ground when you don't have a sensor wired in.  Then it should make the input close to zero if that makes you or your user happier about what LabVIEW sees.

The better solution is to design your VI with some sort of configuration option so that if a channel has a sensor and is a valid input, you check off a boolean.  If there is nothing connected, leave the boolean as False.  Then when you read the channels, you can just zero out the value in software for any channels that aren't enabled.

[rghosh86]

Hi,

I am using sbRIO 9627 for voltage measurement using the on-board 16 bit ADC which have 8 differential channels as input. I am using a total of 8 sensor array for processing the real-time data. We have observed that the readings of the (A0,A1,A2,A3) differential pair varies drastically with (A4,A5,A6,A7). Generally in most of the cases the background noise level of one pair of channel is higher than the other. All sensors are subjected to same input conditions. All the differential channels are used for acquisition. Sampling rate is 1kHz. How to reduce the background noise level of differential channel pairs?  Regards,

[rghosh86]

I am using sbRIO 9627 for voltage measurement using the on-board 16 bit ADC which have 8 differential channels as input. I am using a total of 8 sensor array for processing the real-time data. We have observed that the readings of the (A0,A1,A2,A3) differential pair varies drastically with (A4,A5,A6,A7). Generally in most of the cases the background noise level of one pair of channel is higher than the other. All sensors are subjected to same input conditions. All the differential channels are used for acquisition. Sampling rate is 1kHz. How to reduce the background noise level of differential channel pairs?  Regards,