14
Chapter 5
Operations
General
This section of the manual contains complete operating instructions for the Valhalla Model 4021
Digital Ohmmeter. A description of the front panel controls, connection instructions, and the
theory behind 4-wire resistance measurement is discussed in this section.
Front Panel
Power Switch
Power is applied to or removed from the internal circuits of the 4021 by this switch. On battery
operated units, this switch does
not
need to be turned OFF in order to charge the batteries.
Range Switch
The Model 4021 input range is selected by depressing the desired button on a multi-station
interlocking push-button array located on the right-hand side of the front panel. The push-button
for the lowest resistance range is nearest to the POWER switch. The value of the range is
indicated above the respective button.
Rear Panel
Fuse holder
The fuse-holder is mounted on the rear panel and is designed to protect the internal circuitry. For
AC units, this fuse is a 0.1 Amp Slo-blo fuse. In battery operated units, this fuse is used to
protect the battery pack from excessive charging currents and is a 2 Amp fast-blo fuse. Replace
blown fuses with the same type and rating only!
AC Receptacle
The standard AC receptacle is a three-contact type where the third contact provides a protective
ground. Use the mating power cord provided or its exact equivalent.
Charging Jack
For battery operated units, the battery charging jack is a barrel type and is located on the rear
panel. The center pin of the connector is positive (+). The charging requirements of the internal
battery pack are 6VDC @300mA. The correct charging voltage is supplied by the adapter
included with the instrument. Additional adapters are available as Option "A".
