Simpson 460 4 Series - Resistance Measurements

Operation
4.7 RESISTANCE MEASUREMENTS
4.7.4 The 460 measures resistance from 0.10 to 20 MQ in two
overlapping modes — LO OHMS and HI OHMS. The LO OHMS
mode is useful for measurements which require low power dissi-
pation, low voltage drop (200m V F.S.) across the resistance, and
low open-circuit voltage (less than 1 volt). These features are
especially desirable for in-circuit resistance measurements which
required non-conduction of semiconductor junctions. The low .
open-circuit voltage in the LO OHMS mode eliminates the possi-
bility of damaging certain semiconductor junctions. The HI OHMS
is useful for measurements which require a higher voltage across
the resistance, such as testing conduction in transistors and diodes.
4.7.2. Measurement Procedure:
a. Review the Preliminary Notes and Checks in paragraph 4.3.
b. Connect input test leads to the V-O and COMMON terminals.
c. Depress either the HI OHMS or the LO OHMS function switch.
d. Depress the appropriate resistance range switch as indicated
in Table 4-3.
e. If the resistance being measured is connected into a circuit, be
certain that all power is removed from the circuit and all capaci-
tors are discharged. Check for current paths other than through
the resistance being measured. These paths can result in a meas-
ured value which is lower than the actual value of the resistance
being measured.
f. Connect the test leads to the resistance being measured. Be
careful not to contact adjacent points, even if insulated, par-
ticularly when making high resistance measurements. Some in-
sulators can have relatively low insulation resistance, which
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