11
CMRR (Common Mode Rejection Ratio)
Common mode voltage is voltage present on both the
COM and VOLTAGE input terminals of a DMM, with
respect to ground. CMRR is the DMM’s ability to reject
common mode voltage effects which can cause digit
rattle or offset in voltage measurements.
The instruments have CMRR specifications of 60dB from
d.c. to 60Hz in a.c.V function; and 120dB at d.c., 50 and
60Hz in d.c.V function. If neither NMRR nor CMRR
specification is specified, the DMM’s performance will be
uncertain.
d.c. VOLTAGE function
1) Set rotary switch to position.
2) Insert red (+) test lead into jack and black (–)
test lead into COM input jack.
3) Connect test leads to voltage source and observe the
digital display.
a.c., a.c.+Hz VOLTAGE functions
1) Set rotary switch to position.
2) Insert red (+) test lead into jack and black (–)
test lead into COM input jack.
3) Connect test leads to voltage source and observe the
digital display.
4) Default at a.c. Press button to select a.c.V+Hz
in dual display if required.
d.c., a.c., a.c.+Hz mV functions
1) Set rotary switch to position.
2 ) Default at d . c. Press button to select a . c ., and
press again to select a . c . + H z in dual display
if required.
3) Insert red (+) test lead into jack and black (–)
test lead into COM input jack.
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