Calibration Adjustment Procedure - Fluke PM3082 Service Manual

CALIBRATION ADJUSTMENT PROCEDURE

7 CALIBRATION ADJUSTMENT PROCEDURE
7.1 INTRODUCTION
The calibration adjustment procedure can be split up in two:
- Manual adjustment
- Automatic calibration (AUTOCAL).
All calibration is done with the oscilloscope's cabinet closed. This eliminates calibration inaccuracies
due to temperature changes.
Manual calibration data are protected by a keyword and a seal and must be changed by qualified
personnel only. Some of the adjustments require external calibration equipment. A list of necessary
equipment is given in chapter 6 (performance test). Manual calibration should be done after 2000
service hours or once a year.
Operation of the front panel CAL key activates the automatic calibration. AUTOCAL can only function
usefully if the manual adjustments (especially the 'screen calibrations') are correct. The AUTOCAL
function should in general be activated once a week. AUTOCAL should be used always after
warming-up if the oscilloscope is used in extreme environmental conditions such as very high or low
temperatures while maximum accuracy is needed. AUTOCAL requires no external calibration
equipment.
The calibration adjustment should be started after a warming-up time of 30 minutes.
The most accurate adjustments are done with a well-focused low intensity display.
The calibration parameters are saved after power-down if the memory back-up batteries are installed.
Additionally these parameters can be saved into the instrument's non-volatile memory. This is done
by pressing softkey 'save calibr data' and then activation of the pin hole key. The number of times that
this save action can be done is limited. The memory is full after a number (10x)of actions and needs
to be cleared. Refer to chapter 8 (corrective maintenance) for how to proceed then.
7.2 DARK LEVEL OF CRT
- Press the STATUS and TEXT OFF keys simultaneously: this gives a defined position of the
instrument settings.
- Adjust MTB/VAR to 1 ms/div.
- Select the key sequence 'UTILITY > MAINTENANCE > ENTER KEYWORD'.
- Enter the five digit keyword '3 2 4 1 5'. If correct, an automatic return to the UTIL MAINTENANCE
menu is done.
- Press softkey MANUAL CALIBR.
- Select 'dark' with the TRACK rotary.
- Put the TEXT INTENSITY and TRACE INTENSITY rotaries in minimal intensity position.
- Adjust the A rotary so that the dot at the beginning of the CH1 trace is just invisible.
- Put TEXT INTENSITY and TRACE INTENSITY in normal intensity position again.
- Press softkey RETURN to go to the UTIL MAINTENANCE MENU.
7.3 TRACE ROTATION
- Adjust the INTENSITY TRACE rotary for a well-visible horizontal on the screen.
- Align the CH1 trace exactly in parallel with the horizontal graticule lines using screw-driver
operated TRACE ROTATION rotary.
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