What is the precision of measured values by PXI-4071

[Shivapriya]

Hi,

I am using PXI-4071 instrument. I have some questions:

1. What is the precision of measured values by Read(),ReadMultipoint(),Fetch(),FetchMultipoint() functions?

2. What is the unit for DMM internal temperature niDMM_GetDevTemp() measured value?

3. What is the range for Sample Count in ConfigureMultipoint() API?

Please help me with these queries.

Thanks & Regards,

Priya.

[MarkD-B]

Hi Priya,

  This is intended to answer your question 1).

  The 4071 is a very flexible instrument, and has different precision depending on how fast you need to make conversions.

  As shown in the data sheet, the conversion time increases with more digits of precision.

  You can set the accuracy in one of two ways, either by specifying a range and resolution (in volts, or amps) or by specifying the range and the number of digits. If you are using LabVIEW, it will coerce the value you give upwards to the nearest supported by the card.

e.g.

If you set a range of 300V, with a resolution of 2V, you will actually get 1000V range. Because 1000V range and 2V resolution can be accommodated in 3 digits, the DMM will run at its maximum speed.

Now, if you set a range of 300V and a resolution of 10 uV, you will actually get 1000V range. 1000V range and 10 uV resolution cannot be accommodated in 7 1/2 digits, the maximum, so the DMM will actually only have 100 uV resolution and will run at its slowest speed.

The read and fetch functions will return floating-point values that were measured to the precision determined by the number of digits requested.

All the best,

Mark

[Shivapriya]

Can you tell me where in the datasheet of PXI-4071 i can find this information? Also, can you provide me the answers for the other questions.

Thanks & Regards,

Priya.

[TobiasG]

Priya,

The information you are asking for for your first question is distributed over several places in the 4071 Specifications and the NI Digital Multimeters Help. The precision of a measurement will vary based on the measurement being taken, the range, aperture time, resolution, and several other factors. This article should be helpful, as well as this Digital Multimeter Measurement Fundamentals tutorial.

2. niDMM_GetDevTemp() returns the temperature in degrees Celsius.

3. Valid values for Sample Count are from 1 to 2^31 - 1 (2147483647), inclusive.

Please let us know if you have any further questions.

Regards,

Tobias Gordon

Software Engineer

Precision DC Software

National Instruments