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NOTE: If the measurement was stopped by disconnecting a Kelvin clip,
simply connect it to another object to start the next measurement; It is
not necessary to press the START/STOP button.
6. To display the voltage on the terminals of the resistance instead of the
measurement current, press the DISPLAY key.
Current results are displayed
before pressing DISPLAY button
4.3.1
Measurement Readings
When testing resistive samples, the meter reading will stabilize within the
first few hundred milliseconds. On inductive loads (e.g. small transform-
ers), the measurement reading may take from several seconds to a few
minutes to stabilize and depends greatly on the type of equipment and the
impedance of the equipment under test.
4.3.2
Connections and Readings
The Model 6240 generates a current (I)
from the internal voltage source (V). A
voltmeter measures the voltage drop
V
at the Kelvin probe contact points to
x
the resistance to be measured (R
displays the resistance measurement
(R
) directly using the formula R
x
The result is not affected by the other
resistances encountered in the current
loop (R
, R
, R
i
f
voltage drop induced across R
below the voltage supplied by the source
which is between 5 to 6V. The maximum
admissible lead resistance level is R
helps, as they eliminate the effect of the lead resistance (R
Micro-Ohmmeter Model 6240
), as long as the total
c
) and
x
+
= V
/ I.
x
x
R i = Unit internal resistance
R f = Lead resistance
R c = Contact resistance
remains
x
R x = Resistance to be measured
≈ (V- V
) / I. The use of Kelvin probes
f
x
Voltage results are displayed
after pressing DISPLAY button
C1
Ri
P2
I
V
x
P2
V
C2
).
f
Rf
Rc
Rf
Rx
Rf
Rc
Rf
17
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