Agilent Technologies 34420A, User Manual

Page: 260 / 294

In the power-on state of the meter, offset compensation is enabled. In
some circumstances it may be desirable to turn offset compensation off.
For example if the resistor being measured does not respond quickly to
changes in current, offset compensation will not produce an accurate
measurement. Resistors with very large inductances or resistors with
large values of parallel capacitance would fall into this category. In these
cases the DELAY parameter can be increased to allow more settling time
after the current source is switched on or off, or the offset compensation
function can be turned off.
Power Dissipation Effects
When measuring resistors designed for temperature measurements (or
other resistive devices with large temperature coefficients), be aware that
the meter will dissipate some power in the device-under-test. The effects
of this power dissipation can affect the measurement accuracy.
If power dissipation is a problem, there are two actions you can take: you
can select a higher measurement range to reduce the errors to acceptable
levels or you can set the meter to the low power mode to limit the test
current (
see page 69 ). The following table shows several examples.
Normal Low Power
Range Test Current
DUT Power
(at Full Scale)
Test Current
DUT Power
(at Full Scale)
1
Ω 10 mA 100 m W 10 mA 100 m W
10
Ω 10 mA 1 mW 10 mA 1 mW
100
Ω
10 mA 10 mW 1 mA 100 m W
1 k
Ω 1 mA 1 mW 100 m A 10 m W
10 k
Ω 100 m A 100 m W 10 m A 1 m W
100 k
Ω 10 m A 10 m W 5 m A 2.5 m W
1 M
Ω 5 m A 25 m W 5 m A 25 m W
Chapter 7 Measurement Tutorial
Measurement Techniques and Sources of Error
260