6
9
Chapter 8
.
R
OUTINE
M
AINTENANCE
8.1 General
This Chapter provides general maintenance information and a procedure for calibrating
the ohmmeter. The Model 4176
µ
-ohmmeter should be calibrated on a routine basis
(every 12 months is recommended) to ensure continued accuracy.
Before performing the calibration procedure below, the ohmmeter should be allowed to
warm up at a stable temperature for at least 30 minutes with the covers in place.
8.2 Required Test Equipment
The following equipment is required to perform calibration of the 4176:
1)
Precision resistors with known values within ±0.005%, the following values will
be used: 0.01
Ω
, 0.1
Ω
, 1
Ω
, 10
Ω
, 100
Ω
, 1k
Ω
and 10k
Ω
.
2)
DC voltage standard capable of outputting 10mV, 300mV and 1V. Valhalla
Model 2701C is suitable for the task.
3)
Four wire test lead set.
4)
Precision Digital Voltmeter.
Note: If this equipment is not available, the ohmmeter may be returned to Valhalla
Scientific for calibration traceable to NIST.
8.3 Pre-Calibration Procedure
The calibration adjustments are accessed by removing the top cover of the instrument.
The locations of the adjustment potentiometers are shown in drawing
№
4176-700 (see
chapter 13). Leave the cover in place as much as possible. After each adjustment is
made, the cover should be replaced and the instrument allowed to stabilizing.
Dangerous AC line voltages exist inside the instrument. Use
caution when making adjustments to avoid contact with these
voltages.
