niDMM_Read -> resistance returns "Over range"

[LeroyS]

Hello All,

I need some help with my application using the following software and hardware:
NI CVI 2013
NI PXI-4070

Dmm is configured to read resistance:

     viStat = niDMM_ConfigureMeasurementAbsolute (DMMvisHandle,

                                                                                     NIDMM_VAL_2_WIRE_RES,

                                                                                     NIDMM_VAL_AUTO_RANGE_ON, 0.001)

Software reads resistance:

     if((viStat = niDMM_Read (g_devarray[STE_DMM].visHandle,

                                              NIDMM_VAL_TIME_LIMIT_AUTO, &Reading)) != VI_SUCCESS)
     {
          if(IsNotANumber (Reading))

              Reading = 9.9E36

     }

viStat normaly has a value of 1073356802

niDMM_GetErrorMessage(...) returns "Over range". This is expected for resistance isloation measurements.

Statistical analysis of test results indicates that after 4000 or so reading viStat returns VI_SUCCESS.
(VI_SUCCESS = 0)

Reading is still NaN.

Is there some reason that niDMM_Read would return VI_SUCCESS and a value of NaN?

Thanks for your help.

[ShamWOW!!]

That reading of NaN tends to come up when the read is succsesful but is over the range of the DMM. Around what range does your value start becoming NaN vs actually having values?

Best,

Shamik C

Applications Engineer 

National Instruments

[LeroyS]

ShamWOW:

We can make readings of 10 MegOhms, we verify this durring system calibration.

Our team is wondering why 1 out of 4000 readings is VI_SUCCESS even though the
reading is clearly Over range (NaN)?

Thanks

PXI-4070 is configured to: 2-Wire Resistance, "Auto-Range", resolution 0.001.
viStat = niDMM_Read (with "Auto-settling time") returns reading NaN.

99.99% of the time viStaus = 1073356802 (which translates to "Over range").

1 out of 4000 times viStatus = VI_SUCCESS.
The returned reading is still NaN.