On the 10 and 1 millivolt ac ranges, an
a. Place the ME-202C/U controls to the following
observed offset of 200 microvolt is normal,
This is the internal noise of the voltmeter,
(1) POWER switch to ON.
a n d will not affect the accuracy of
(2) RANGE switch to 10.
measurements above this level.
(3) NULL SENS switch to .01 (.001 if the R is
3-5. Differential Voltmeter Operation
greater than 1010).
Operate the voltmeter as an ac or dc differential
(4) MODE switch to +DC.
(5) Readout dials to 0.00 00.
a. Determine the approximate value of the
measured voltage by performing the TVM mode
HI and LOW INPUT terminals. Use short isolated
b. Place the MODE switch to the respective
between the leads.
polarity observed on the TVM mode measurement
c. Rotate the readout dials to botain a meter
and set the readout dials to the TVM measurement
deflection of - 1 and use the formula given in d
value. If an ac measurement is being made, leave the
below to determine the value of the unknown
MODE switch in its AC position.
c. Place the NULL SENS switch to successively
d. The unknown resistance is as follows:
high null sensitivity positions and adjust the readout
dials to obtain a center-zero meter indication.
The INPUT ground terminal is directly connected to
the chassis of the instrument to provide a convenient
Rx = Unknown resistance
connection to earth ground whenever the line cord is
Ero = Readout dial voltage
connected to line power. Whenever measurements of
voltages having a reference other than ground, but
Em = meter deflection in volts (pro-
not exceeding 500 volts, are performed, the shorting
portional to selected NULL SENS).
link between the LOW INPUT and ground terminal
must be removed or damage to the measurement
343. Operation Under Unusual Conditions
source, or the ME-202C/U, or both, may occur.
3-7. High Resistance Measurements
under which performance of the unit is specified.
Operation or storage beyond those limits, or under
measurements of high resistances from 10 to 106
conditions of sand, salt spary, etc, is not recom-
megohms with a typical accuracy of 05%. The