OHMS
CURRENT
SOURCE
Measurement
RESSTAMCE
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8840A
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OHMS CURRENT SOURCE
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VOLTAGE SENSE
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Figure
44.
4-Wire
Ohms MeWrement
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1-utoria~
MEASUREMENT
b.
If the dielectric is poor (i-e., has
high
dielectric
4-wire ohms function. Press the range buttons to se&ct any
absorption), the voltage across the capacitor will
of the cuhent levels shown in Table 4-1.
I
be
significantly above zero.
I
4-12.
A
PRECISION CURRENT SOURCE
The ohms current source (the internal current source used
in the ohms functions) makes a useful troubleshooting tool
in itself.
It
has excellent linearity and temperature stability.
Its compliance voltage is typically
5V
in the lower four
ohms ranges, and
12V
in the upper two ohms ranges. The
inputs are protected against accidental applications of volt-
age up to
300V
rms.
To use the ohms current source, connect the test leads to
the HI and
LO
INPUTS,
and select either the 2-wire or
The ohms current source can
be
used to troubleshoot
circuits by injecting current into selected nodes,
the circuits to
be
in a specific test state. For
exam
ohms current source
can
be
used to set or modify
of amplifipr circuits. The current level
can
be
simply by changing range.
The ohms cunent source can also be
used
to test mA or
WA panel meters. The accuracy of the current
sowce
is
more than enough to verify panel meters, whose a+xracy
is typically
1%
to
5%.
To test an analog panel
1
meter,
simply connect the current source across the meter move-
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