3 channels from daq assistant not working properly

[Nadweb]

I'm using a DAQ assistant to measure 3 channels on a NI9209 in a cRIO9056. The NI9209 is recieving voltages from an adjustable power source for testing (voltages will be from three pressure sensors when VI is finished). The power source is wired to the 9209 single ended, not differential, the DAQ assistant is setup appropriately.

When only one channel receives a voltage, it works properly, I can display the correct voltage. When multiple channels receive voltages, the DAQ assistant doesn't measure properly, and the displayed voltages are all incorrect. Not even really close. I don't understand this problem, and would really appreciate any ideas/assistance.

Thanks in advance!

P.s. Sorry I dont have my code posted at the moment. It is a simple VI with an assistant, splits the channels, some simple conversation math from voltage to pressure, and indicators on the voltages and converted pressures

[GerdW]

Hi Nadweb,

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@Nadweb wrote:

P.s. Sorry I dont have my code posted at the moment. It is a simple VI with an assistant, splits the channels, some simple conversation math from voltage to pressure, and indicators on the voltages and converted pressures

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Sorry, but without the code we cannot tell you which problems/errors hide in your code!

Spoiler

I guess there is a problem in one of those ExpressVIs you seem to use.
The simple solution could be to get rid of all those ExpressVIs!

[Nadweb]

I've tried it without the express VI's because that's usually what people say to do. Same result. One channel works at a time, they dont all work together. I think it's maybe more of a hardware issue. The code is simple, read the single ended voltage and a numerical indicator. 

I saw in another forum post to ground every unused input. I may try that, but other than that I'm out of ideas 

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@GerdW wrote:

Hi Nadweb,

---

@Nadweb wrote:

P.s. Sorry I dont have my code posted at the moment. It is a simple VI with an assistant, splits the channels, some simple conversation math from voltage to pressure, and indicators on the voltages and converted pressures

---

Sorry, but without the code we cannot tell you which problems/errors hide in your code!

Spoiler

I guess there is a problem in one of those ExpressVIs you seem to use.
The simple solution could be to get rid of all those ExpressVIs!

---

---

@GerdW wrote:

Hi Nadweb,

---

@Nadweb wrote:

P.s. Sorry I dont have my code posted at the moment. It is a simple VI with an assistant, splits the channels, some simple conversation math from voltage to pressure, and indicators on the voltages and converted pressures

---

Sorry, but without the code we cannot tell you which problems/errors hide in your code!

Spoiler

I guess there is a problem in one of those ExpressVIs you seem to use.
The simple solution could be to get rid of all those ExpressVIs!

---

[GerdW]

Hi nadweb,

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@Nadweb wrote:

but other than that I'm out of ideas 

What about the idea of attaching some code?

[NIquist · Accepted solution]

This does sound like a hardware problem.  Probably wiring.  Dump the code for now, open NI-MAX, goto Devices and Instruments, select your 9209 and open the Test Panels.  You can then change channel, mode, configuration, etc. and troubleshoot without messing with code.

The grounding every other channel trick is to deal with "Ghosting".  That happens when adjacent channels pick up their neighbors signals through the multiplexor circuit.  If your wiring is correct you shouldn't have any problems with that.

Read through this and check your wiring and make sure it's right for the Input Configuration you are using.  As a bonus, learning this now will help you make good design decisions that will become important when you start working with your sensors and need to minimize noise and interference.

https://www.ni.com/en-us/support/documentation/supplemental/06/field-wiring-and-noise-considerations...

[Nadweb]

Thank you for the reply! You are correct, wiring was the issue.

It turned out to be a dumb (on my part) wiring problem. I wired two inputs with a single power supply and accidentally crossed my wires such that one negative wire went to ground and one went to the port, and one positive wire went to ground and the other to the port. I switched it so both negatives went to ground and both positives went to the ports. Much better!