ETI PI-800 Instruction Manual page 48

Electrical Test Instruments PI-800 and PI-1600
Section V – Service Information and Documentation
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Therefore, proper operation and calibration should be checked at regular inter-
vals, and adjusted if proper equipment is available. The manufacturer's recom-
mended calibration interval is (1) one year.
The inherently delicate nature of electronic circuitry and metering make it gen-
erally inadvisable to leave the MAC-21 fastened to the breaker test set if it is be-
ing transported under conditions of extreme shock and vibration. The compo-
nent parts should be disconnected, covers attached, and carried or shipped sep-
arately. Suggested periodic maintenance consists of the following:
1. Clean the lenses of the LED displays with a plastic cleaner.
2. Clean the front panel with a soft brush and cloth.
3. Perform basic field operational check as described below.
Field performance check of the MAC-21 may be performed as follows:
1. Obtain a current measuring calibration standard capable of reading TRUE-
RMS current up to at least 1000 Amperes to an accuracy of at least 0.25%.
2. Set up the breaker test set for normal breaker testing. If adjustments are
anticipated, remove the MAC-21 from the test set and remove the top cover.
3. Connect the calibration standard to the desired output tap. If cables are
used, it is recommended that they be twisted so as to minimize radiation
and pickup of stray magnetic fields.
4. Apply power to test set, and allow at least one minute for circuits to stabilize.
5. Check ammeter zero in all ranges. If reading on current meter is greater
than 1% of Full Scale, internal zero adjustment may be required.
6. Set MAC-21 Range to 1000 A, and adjust output of breaker test set to exactly
800 Amperes. If Coarse Tap is 1, and Output Control Vernier is less than 50%,
additional resistance must be added to output circuit. This is important, be-
cause waveform distortion is more prevalent at lower levels.
7. If the MAC-21 reading differs from the standard by more than rated accu-
racy, adjust the gain potentiometer on the analog board for proper reading.
If an error of more than 5% is noted, and unit has been in service, the accu-
racy and validity of previous tests may be questionable; otherwise, there may
be a problem in the test setup.
8. Check accuracy at 200, 400, 600, and 1000 Amperes.
9. Adjust the current to zero, and press RESET key.
10. Raise the current slowly, until the timer begins to run. This is the Current
Latch Threshold, which should be about 5% of full-scale range.
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