Seaward DO4000 User Manual
Page 6
Operating Instructions
Digital Ohmmeter DO4000 Series
4
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 I terminals, and the
voltage drop across the Rx is measured at the U 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
carefully selected internal resistance standards.
4. Case Design
The case is ruggedly constructed from abs plastic (UL 94 HB). The front panel is
a reverse printed polycarbonate overlay with clear and unambiguous text. The
batteries are housed in a removable cassette, which enables quick and easy
replacement.
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 all power sources. In
the event of a fault occurring, the instrument should be returned to our
factory or Agent.
A 1 AMP fuse located on a holder on the main printed circuit board protects the
input circuits. Access is gained by removing the rear cover. Only replace with the
correct fuse type as below.
1A (FF)
700V rms
HBC