Keysight E1412A, Service Manual

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Keysight E1412A Digital Multimeter Service Guide 103
Interpreting Multimeter Specifications E1412A Multimeter Specifications
Interpreting Multimeter Specifications
This section is provided to give you a better understanding of the terminology
used and will help you interpret the multimeter's specifications.
Number of Digits and Overrange
The “number of digits” specification is the most fundamental, and sometimes,
the most confusing characteristic of a multimeter. The number of digits is equal
to the maximum number of “9's” the multimeter can measure or display. This
indicates the number of
full digits . Most multimeters have the ability to
overrange and add a partial or “½” digit.
For example, the E1412A can measure 9.99999Vdc on the 10V range. This
represents six full digits of resolution. The multimeter can also overrange on the
10V range and measure up to a maximum of 12.00000Vdc. This corresponds to a
6½-digit measurement with 20% overrange capability.
Sensitivity
Sensitivity is the minimum level that the multimeter can detect for a given
measurement. Sensitivity defines the ability of the multimeter to respond to
small changes in the input level. For example, suppose you are monitoring a
1mVdc signal and you want to adjust the level to within
 1mV. To be able to
respond to an adjustment this small, this measurement would require a
multimeter with a sensitivity of at least 1
 V. You could use a 6½-digit multimeter
if it has a 1Vdc or smaller range. You could also use a 4½-digit multimeter with a
10mVdc range.
Note that the smallest value that can be measured is different from the sensitivity
for ac voltage and ac current measurements. For the E1412A, these functions are
specified to measure down to 1% of the selected range. For example, the
multimeter can measure down to 1 mVac on the 100 mVac range.
Resolution
Resolution is the numeric ratio of the maximum measurable value divided by the
minimum measurable value on a selected range. Resolution is often expressed in
percent, parts-per-million (ppm), counts, or bits. For example, a 6½-digit
multimeter with 20% overrange capability can make a measurement with up to
1,200,000 counts of resolution. This corresponds to about 0.0001% (1 ppm) of
full scale, or 21 bits including the sign bit. All four specifications are equivalent.