Calibrating The Tester; Introduction; Entering Calibration Mode - Fluke 39 Service Manual

39/41B
Service Manual

4-14. Calibrating the Tester

The Tester allows closed-case calibration using known reference sources. The meter
automatically prompts you for the required reference signals, measures them, calculates
the correction factors, and stores the correction factors in the nonvolatile calibration
memory.
The Tester has a normal calibration cycle of 1 year. If the Tester fails the performance
test or has been repaired, it should be calibrated. To meet the instrument specifications,
listed in Chapter 1, the Tester should be calibrated with equipment meeting the minimum
specifications given in Table 4-1.

4-15. Introduction

The Tester is calibrated using the calibration screen. Two factors are used to correct each
a/d converter reading: offset and gain. AC voltages are used as inputs to both the offset
and gain calculations. During the offset measurement, the instrument calculates the DC
value of the AC input. This insures that the DC values reported, when AC is present, are
correct.
CV is the calibrated value. Advalue is the present reading from the a/d converter. GSF is
the gain scale factor and Offset is the value from the calibration sequence.
The basic calibration consists of sets of steps for Volts (banana jacks) and Amps (BNC
inputs). Both inputs are calibrated using an AC Volt Reference Source.
Do not apply current sources to the Tester's Clamp Probe
(BNC) connector.
The entire calibration process must be completed before the new calibration factors can
be stored in nonvolatile memory. If the calibration process is discontinued prior to
completion, no changes are made to nonvolatile calibration memory.

4-16. Entering Calibration Mode

To put the Tester in the calibration mode and display the calibration screen, proceed as
follows:
1. Allow the Tester to stabilize in an environment with an ambient temperature of 18 to
The Cal Enable switch is located in the battery compartment of the
instrument beneath a calibration seal.
2. Remove the Tester's battery access lid and batteries (Figure 4-2). Remove the
4-12
CV = 2 × [(Advalue × GSF) + Offset]
28 degrees Celsius and relative humidity of less than 70% for at least four hours.
calibration seal to reveal the calibration access hole.
Caution
Note