User`s guide

338
Chapter 8 Specifications
To Calculate Total Measurement Error
To Calculate Total Measurement Error
Each specification includes correction factors which account for errors
present due to operational limitations of the internal DMM. This section
explains these errors and shows how to apply them to your
measurements. Refer to “Interpreting Internal DMM Specifications,”
starting on page 340, to get a better understanding of the terminology
used and to help you interpret the internal DMM’s specifications.
The internal DMM’s accuracy specifications are expressed in the form:
(% of reading + % of range). In addition to the reading error and range
error, you may need to add additional errors for certain operating
conditions. Check the list below to make sure you include all
measurement errors for a given function. Also, make sure you apply the
conditions as described in the footnotes on the specification pages.
• If you are operating the internal DMM outside the 23 °C ± 5 °C
temperature range specified, apply an additional temperature
coefficient error.
• For DC voltage, DC current, and resistance measurements, you may
need to apply an additional reading speed error.
• For AC voltage and AC current measurements, you may need to
apply an additional low frequency error or crest factor error.
Understanding the “ % of reading ” Error The reading error
compensates for inaccuracies that result from the function and range you
select, as well as the input signal level. The reading error varies
according to the input level on the selected range. This error is expressed
in percent of reading. The following table shows the reading error
applied to the internal DMM’s 24-hour DC voltage specification. .
Range Input Level
Reading Error
(% of reading)
Reading Error
Voltage
10 VDC
10 VDC
10 VDC
10 VDC
1 VDC
0.1 VDC
0.0015
0.0015
0.0015
150 V
15 V
1.5 V
34970A Refresh UG.book Page 338 Wednesday, February 17, 2010 12:34 PM