NI4070 DMM resistance measurement error

[lakeshoretest2005]

Hello Support,

I am in need of troubleshooting help with a NI4070 DMM in a mainframe chassis which is giving me incorrect readings in resistance and voltage measurement mode. I use the DMM in an automated lab test environment. I am not aware of any overstress conditions my testing has presented to the DMM.

Measurement software:
Labwindows or DMMSFP 2.0 (the soft front panel program courtesy NI). I use either program (not both at the same time) and get an error in either program. Previously ohmic measurements using labwindows were good, but now failing. I am now using DMMSFP 2.0 with resistors applied directly to the banana jack inputs to test the integrity of the DMM.

Symptoms:
1. 2-wire resistance measurement is failing using DMMSFP 2.0. Under open circuit conditions, the measurement reads very high ohms or OVLD which is OK. When I apply a resistance to the 2-wire inputs, the measured value reported is not what I expect. Applying 50 ohms, I read less than one ohm. Applying 1k, I read less than 1 ohm. Using an independent hand held DMM, I verified the resistance of the 50 ohm and 1k resistors - I read slightly less than 50 ohms and 1k - so I know the components are not to blame.

2. Voltage measurement is failing using DMMSFP 2.0. I used a power supply to apply +2.6 volts to the DMM inputs. Using DMMSFP 2.0, I read a negative voltage with ~4.5 volts magnitude.

Questions:
1. Is there diagnostic software I can execute that might validate or invalidate the instrument's integrity?

2. Is this truly a hardware problem? Has anybody seen this failure type? What would cause the failure?

3. If the root cause is hardware, what are my options? I am part of a large organization and have inherited the DMM and PXI system, so I'm not sure who at NI to contact. I believe it has been less than one year since the DMM has been purchased, is the card still under warranty? Will the card be repaired? What is a typical lead time for repair?

Thank you very much for any help.

Regards,

Mark

[Alan_L]

Mark,

Given the tests you have already run, it certainly does appear that something has happened to cause the hardware to internally malfunction. If it was in fact shipped from our facility less than a year ago, then it is covered under warranty. As far as a preliminary diagnostic you can perform, I recommend first upgrading to the latest software driver and running a self-test by right clicking on the device entry in MAX and choosing "Self-Test." I've linked the latest drivers you'll need below (you can check what versions you already have under the "Software" category in MAX). Whether or not the self-test returns an error, if you still are making poor measurements I suggest you contact us to have your board repaired. To do so, just point your web browser to http://www.ni.com/support and choose "Option 2" to open a repair request.

DMM Driver:
NI-DMM 2.3.1 (requires NI-DAQ 7.2 or later)

Thank you and please let me know if I can be of further assistance.

Best Regards,
Alan L
Applications Engineer
National Instruments

[lakeshoretest2005]

Alan,

Thank you for responding. I am trying to follow your instructions to check the software revision and self-test the DMM instrument, however I am having some difficulty.

Within MAX, I can see the device "NI 4070 for PXI (Device 5)", but when I right click I only see three options: Test Panel, Delete, or Properties. The "Test Panel" option is grayed out and unavailable for me to use. Is this the option I want? How do I enable this feature?

Also, when trying to determine the current software version of the DMM, in MAX I expand the software tree and see: CVI Run-time, IVI Engine, Labview run-time, MAX, Measurement Studio, NI Spy, NI-488.2, NI-DAQ, NI-PAL, NI-VISA. I don't see any entries related to a DMM. Am I missing something? Where can I find the DMM software revision information?

Your help is appreciated.

Regards,

Mark

[Alan_L]

Mark,

I'd like to troubleshoot with you in person so that we can most expediently determine what is going wrong. What is the best way to reach you directly?

Thanks,
Alan L
Applications Engineer
National Instruments

[lakeshoretest2005]

Alan,

Thank you very much. I would appreciate your personal support.

Please contact me at lakeshore0505-test@yahoo.com. I can provide you with more detailed contact information at that address.

Regards,

Mark