DO4A Issue 3/2001
5
3.
Measuring Principle
The measurement is true 4 terminal, using the Kelvin principle. A stable current is
produced across the resistance to be measured via the C terminals, and the voltage
drop across the Rx is measured at the P terminals. This potential drop is then
compared against the voltage drop across internal standards, the ratio of these is then
converted to the resistance value of Rx and displayed in ohms on the digital display.
High accuracy and long term stability is achieved by using our own manufactured
internal resistance standards.
4.
Case Design
The case is ruggedly constructed and is a painted aluminium shell with a strong
internal sub-frame. The front panel is a reverse printed polycarbonate overlay with
clear and unambiguous text. The case is painted anthracite grey, and the tilt handle
means that the instrument can be positioned for easy viewing.
5.
Maintenance
Normally no maintenance is required other than cleaning with a moist cloth. Avoid
aggressive detergents or solvents.
CAUTION: Before any maintenance, repair or exchange of parts or
fuses, the instrument must be disconnected from the mains supply and all
power sources. In the event of a fault occurring, the instrument should be
returned to our factory or Agent. A mains fuse is fitted to the mains inlet
socket on the rear panel, and should be replaced if necessary.
CAUTION: Disconnect mains lead and all connecting leads, before
removing fuse holder. Replace only with correct fuse type ie. according
to
the following chart
Line
Range
Fuse (250V)
Fuse (250V)
Voltage
VAC
IEC 127
UL198 G
Selection
47-63Hz
5 x 20 mm.
0.25"X1.25"
100V
87-110V
630mA (T)
800mA Slo-
120V
104-132V
Blo
220V
191-242V
315mA (T)
400mA Slo-
240V
209-264V
Blo
Maximum Input Power : 20VA
