Electrical Test Instruments MAC-21
Section III
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MAC-21
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Copyright(C) 1994-2021 Electrical Test Instruments, LLC All Rights Reserved
Page III-4
SECONDS key:
This key normally selects the SECONDS time base. If the PRESET
mode is selected, this key is used to LOWER the preset time limit by decrements of
1.000 second (5.000 seconds above 10.00) with the SECONDS time base, or 1.0 cycles
with the CYCLES time base. If it is held, the reading will decrease at a rate of about 5
intervals per second. If a preset time limit was set in SECONDS mode, the output will
be turned off within 200 milliseconds of the limit. SECONDS or CYCLES time base
may be selected at any time before, during, or after a test.
CYCLES key:
This key normally selects the CYCLES time base. If the PRESET mode is
selected, this key is used to RAISE the preset time limit by increments of 1.000 sec-
onds (5.000 seconds above 10.00) with the SECONDS time base, or 1.0 cycles with the
CYCLES time base. If it is held, the reading will increase at a rate of about 5 intervals
per second. If a preset time limit was set in CYCLES mode, the output will be turned
off within several milliseconds after the limit has been reached. SECONDS or CYCLES
time base may be selected at any time before, during, or after a test.
MEMORY key:
This key toggle the MEMORY mode, indicated by illumination of its
LED. When in CONTINUOUS mode (LED off), the current display always reads the real-
time continuous output current of the test set. In MEMORY mode (LED on), the cur-
rent display will read the continuous output current until the test is complete. At this
time, the LED will flash, and the display will read the computed true-RMS value of the
entire current pulse for the duration indicated on the TIME display. This key may be
pressed at any time before, during, or after the test, to toggle between the two
modes.
As described above, pressing the STOP key provides access to display of peak RMS
and last average RMS current.
1000 A range key:
This key selects the 1000 ampere range, which provides best accu-
racy of readings up to about 1000 amperes. Nominal currents close to this limit, when
applied to the device under test, will sometimes cause higher peak currents, causing
the display to read "OVER", indicating an overrange condition. If this happens, select
the next higher range. Pressing any range switch will also RESET the MAC-21.
5 KA range key:
This key selects the 5.000 KA range, for output currents up to about
5,000 amperes. See above for information common to all ranges.
25 KA range key:
This key selects the 25.00 KA range, for output currents up to about
25,000 amperes. See above for information common to all ranges.
100 KA range key:
This key selects the 100.0 KA range, for output currents up to about
100,000 amperes. See above for information common to all ranges.
CONTINUITY lamp:
This LED lights when continuity is detected at the CONTACTS
binding posts in N.O. and N.C. modes. The beeper will also sound whenever contacts
change state.
CONTACTS/REMOTE jacks:
These jacks provide a low-power AC signal which detects
continuity in N.O. and N.C. modes, or is used with a pushbutton cord switch for
