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-2
MAJOR PARTS IDENTIFICATION AND OPERATION
MAC-21 Control Panel
TIME DISPLAY:
This 4-digit LED display normally indicates the elapsed time of a cur-
rent pulse. In SECONDS mode, it displays time up to 9.999 seconds, then auto ranges
to 99.99 seconds, 999.9 seconds, and 9999 seconds. In CYCLES mode, it reads time
(based on 60 Hz), up to 999.9 cycles, then auto ranges to 9999 cycles. If time exceeds
maximum display capacity (10,000 seconds or 10,000 cycles), the display will read
"OVER". In PRESET mode, the display indicates the maximum time of initiation (ON
time), in either cycles or seconds. A reading of zero disables the PRESET function and
allows any time.
CURRENT DISPLAY:
This 4-digit LED display indicates the output current. In
CONTINUOUS mode, as well as in MEMORY mode before and during a test, the dis-
play indicates true-RMS output current in real time. After completion of a test, in
MEMORY mode, the display shows the true-RMS value as computed over the entire
length of the pulse. This mode is indicated by a flashing LED on the MEMORY key. If a
reading exceeds the maximum value for the selected range, the display will read
"OVER".
This display is also used When the time base is in SECONDS mode, press the
STOP key to display the last average RMS value displayed in CONTINUOUS mode. This
is useful for pickup tests. It may not be accurate for times less than 1 second.
INITIATE key:
This key is used to turn ON the output of the test set. The LED in the key
indicates that the MAC-21 is attempting to turn the output ON, but other conditions
(such as interlocks) could keep the output from actually turning on. In MOMENTARY
mode, the key must be held to keep output current on. In MAINTAIN mode, once cur-
rent is detected, the output will stay on until the breaker trips, or the STOP or RESET
button are pressed. The MAC-21 must be RESET in order to initiate output, and in N.C.
or N.O. contact modes, the contact status (continuity) must indicate that the breaker
is closed. If the output on time exceeded the PRESET time, as indicated by flashing of
the PRESET key LED, the INITIATE key will automatically reset the MAC-21 and turn
the output on.
STOP key:
This key is used to turn the output of the test set OFF. Its LED indicates
that output is not being turned on by the MAC-21, but other conditions could cause
output voltage to be ON. Use of this key is usually necessary only when in MAINTAIN
mode, and it is necessary to abort the test before the breaker trips. NOTE: It is im-
portant to realize that the interlock system of the circuit breaker test set may also
turn the output off, but it will turn back ON when the interlock condition is cleared (in
N.O. and N.C. modes only).
RESET key:
This key reset the displays on the MAC-21, and arms the pulse reading sys-
tem. The LED on the key indicates that the system is reset and armed
.
RESET also
