NI myDAQ voltage issues

[monty_monty]

greetings, 

I am having issues with the output voltage only myDAQ. For the +15, -15, and 5V output I am only getting a reading of 2.30 Volts at all 3 of these nodes.. Any suggestions are appreciated.

[jonathanadalin]

Could you provide more information on how you're measuring the voltage on the three nodes of the myDAQ? Have you tried using another measurement tool?

[mwong017]

I'm having a similar problem with the analog outputs. I have multiple MyDAQs for my undergraduate teaching labs in University. On a few of them the voltage from the AO0 or AO1 channels give DC voltage of between 2.5 to 3.5 volts when I measure directly the pins using a multimeter. This is without using any waveform or the DC level software. The default voltage I'm getting from the pins is this 2.5 to 3.5 volts.

But if I put a load (saw 1 kOhm) resistor across the AO0 and aGND pins then the voltage between the AO0 and AGND will give the proper voltage that I set using the DC level software.

[DuncanW.]

Hi mwong017,

Could you elaborate on the measurement setup that gives an unexpected or floating voltage at the AO pins on your device? Do you need to use the device in this configuration for your system?

Also, I'm confused by what you mean by "without using any waveform or the DC level software". To me, this suggests that you are measuring the outputs of the device without driving them, which probably explains why these outputs appear to be floating.

With a little more information about your system, I'm sure we can figure out what is going on and get it resolved.

Best,

Duncan W.

Applications Engineer

National Instruments

[mwong017]

Hi there Duncan,

Thanks for your reply. I've contacted NI support with my question and I'm currently getting troubleshooted by another applications engineer. However for interest I will elaborate on my setup.

I have about 75 myDAQs running in my teaching labs and as of now, about 10 are experiencing this problem where the analog output is not working properly. For some it is both AO0 and AO1 and for some it is one or the other. When I measure the DC signal (using either a Fluke or the myDAQ DMM) between the AO0 channel and AGND, I get this floating voltage that is between 2.5 or 3.5 Vdc. When I use the DC level application to adjust the output voltage, the signal does not change unless I set the voltage to higher than the floating voltage I read. Example, on on myDAQ the signal is 3.184 Vdc between AO0 and AGND. When I set the level of DC level to 3.5 V then my multimeter will read correctly 3.5 V but if the setting is 2.5 V on DC level then the multimeter will still read 3.184 V.

When I put a resistor (say 0.5 or 1 kOhm) between AO0 and AGND and read the signal between AO0 and AGND or the two ends of my resistors then I get the exact reading that my DC level is set to.

In addition, when I try this test of Analog I/O from this video: https://www.youtube.com/watch?v=8H5BY-ZerV0

I get no reading on my oscilloscope even if I change the peak to peak signal to something higher than 3.184 V. 

So I have a feeling that there is something fishy going on with my analog outputs. I've tried to change the black pin connectors to new ones and I've tried the faulty myDAQs on different computers and with different multimeters and all with the same results.

Thank you very much for any help you can provide.

[DuncanW.]

Hmmm that does sound like something is broken in those devices, but I would be hesitant to jump to that conclusion since this behavior is happening with a number of devices.

If you are already working with another applications engineer, then I would suggest that you just continue working with them and we will work to get your issue resolved.

-Duncan

[AIMXXI]

Hi, could you solve the problem? I am having the same issue too. Once I set my DC level voltage more than 2 Volts, my DMM just reads 2.1 Volts 

[mwong017]

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@AIMXXI wrote:

Hi, could you solve the problem? I am having the same issue too. Once I set my DC level voltage more than 2 Volts, my DMM just reads 2.1 Volts 

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Hi there, unfortunately not. I went through several weeks of troubleshooting with a pair of NI applications engineers (by email and phone) and finally I had to send in one unit for (out-of-warranty) RMA repair. The RMA team (based in Hungary) performed the repair but did not provide me details about what was actually wrong. The only note I received from RMA team was "Component failure -- replaced component (Power Supply) (DIO TIO)".

When I asked the NI engineer if they could follow up with the RMA notes, they said that "multiple components were replaced including an isolation transformer, a couple DAC chips, and an amplifier among others". The total cost for the RMA repair was about $200 USD. I still have a few other faulty units but have not decided yet to send them for RMA repair or just replace them with new units.

If you are thinking about troubleshooting with an NI engineer, the reference number for my case was #7761978, if it helps.