Interpreting Accuracy Specifications; 24-Hour Accuracy; 90-Day And 1-Year Accuracy; Temperature Coefficients - Fluke 8845A Calibration Manual

8845A/8846A
Calibration Manual

Interpreting Accuracy Specifications

The following sections provide a clearer understanding of specifications over time and
with temperature variations.
24 Hour Accuracy
-
The 24
measurement range for short time intervals and within a stable environment. Short
accuracy is usually specified for a 24
90 Day and 1
-
The longer duration accuracy specifications are valid at the calibration temperature (T
±5 °C temperature range. These specifications include the initial calibration errors plus
the Meter's long

Temperature Coefficients

Accuracy is usually specified at the calibration temperature (T
range. This is a common temperature range for many operating environments. Add
additional temperature coefficient errors to the accuracy specification if the Meter is
operated outside the ±5 °C temperature range (the specification is per °C).

Configuring for Highest Accuracy Measurements

The measurement configurations shown below assume that the Meter is in its power
or reset state. It is also assumed that auto-ranging is enabled to ensure proper full-scale
range selection.

DC Voltage, DC Current, and Resistance Measurements

Select NPLC and 100 (NPLCs) for highest instrument resolution and accuracy.
For the best dc voltage accuracy, set INPUT HIGH INPUT Z (impedance) to GOhm (for
the 100 mV, 1 V, and 10 V ranges).
For the best resistance measurement accuracy, use the 4
For 2
remove thermal EMF and offset errors.
Zero the test lead resistance for 2
remove any interconnection offset for dc voltage measurements.

AC Voltage and AC Current Measurements:

Set the AC FILTER to 3 Hz: SLOW.

Frequency and Period Measurements:

Set the GATE TIME to 1 sec.
1-22
hour accuracy specification indicates the Meter's relative accuracy over its full
-
Year Accuracy
-
term drift errors.
-
wire ohms, dc voltage and dc current measurements, set AUTOZERO to ON to
-
hour period and for a ±1 °C temperature range.
-
wire ohms function (4W).
-
wire and 4-wire ohms measurements and zero to
-
term
-
cal
) ±5 °C temperature
cal
on
–
)