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8842A
Instruction Manual
6-18
1. If you just completed the Offset and Gain or High-Frequency AC Calibration for an
entire function (not just one range), the range buttons can be used to change ranges in
order to verify all ranges were calibrated correctly.
2. If you just calibrated an individually selected range, pressing another range button
begins the Offset and Gain Calibration procedure for the new range.
3. You can use the RATE button to verify the calibration at other reading rates.
CAUTION
It is still possible to erase the calibration memory while the
8842A is taking verification readings.
6-19. ERASING CALIBRATION MEMORY
The 8842A allows you to erase some or all of the correction constants stored in
calibration memory (U220). It is recommended that you erase the entire calibration
memory before beginning calibration if the calibration memory is replaced or
accidentally altered. The capability of erasing particular parts of the memory is mainly
intended as a troubleshooting aid to the technician.
CAUTION
Once the calibration memory is erased, the 8842A must be
recalibrated.
To erase all or part of the calibration memory, proceed as follows:
1. Press the front panel ERASE button. The display should show the erase prompt "cl"
(for "clear"). If you do not press another button within 1-1/2 seconds, the 8842A
returns to its previous state.
2. To complete an erasure, press one of the following buttons within 1-1/2 seconds of
pressing the ERASE button:
a. STORE -- Erases the entire memory.
b. A/D -- Erases the A/D Calibration constants
c. Any function button -- Erases the Offset and Gain Calibration constants for all
ranges of that function.
d. HF AC -- Erases the High-Frequency AC Calibration constants.
3. After an erasure is finished (a complete erasure takes about 3 seconds), the 8842A
returns to one of the following states:
a. After complete erasure: Begins A/D Calibration.
b. After A/D erasure: Begins A/D Calibration.
c. After Offset and Gain erasure: Begins Offset and Gain Calibration for erased
function.
d. After High-Frequency AC erasure: Begins High-Frequency AC Calibration.
6-20. TOLERANCE CHECK
The 8842A automatically checks that the reference input is near the value prompted. This
minimizes common errors such as applying a reference source with the wrong sign. If the
reference input exceeds the tolerances shown in Table 6-13, the 8842A displays ERROR
41.