5
MEASURING WITH THE DO7PLUS
5.1
Connecting to the DO7PLUS
The DO7PLUS uses a four terminal method of measurement which eliminates errors due to
lead resistance. The measuring leads plug into the four front panel safety sockets. The
sockets are U, U, +I, & I. Connections to the resistance to be measured should be
as per Fig: 5.1.1
Fig: 5.1.1 Connection diagram
HINT:
It is important to connect the I (current) leads outside the U (potential) leads
5.2
Connecting to the resistance
The Digital Microhmmeter DO7PLUS employs a four wire method of measurement, i.e. it is
necessary to make four connections to the resistance under test. The instrument is supplied
with four leads; two for the potential connections which are made across the test resistor at
the points between which the resistance is to be determined; and two for the current
connections which connect the test resistor to the current supply circuit.
Connect to the resistance under test as shown in figure 5.1.1, Cleanliness is important and if
the sample is not clean, a rub with an abrasive paper to remove oxides is recommended.
It is not always possible to use the combined current and potential crocodile clips (Kelvin
clips), in which case test leads with spade tags, or special fixtures may have to be made to
suit the particular application. We offer a variety of different lead and fixture types which are
list in section 9
Rx
+I
+
U
-I
-
U
Operating Instructions
Digital Microhmmeter Type DO7 PLUS
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