34410A/11A User’s Guide 103
Measurement Tutorial 4
Removing Test Lead Resistance Errors
To eliminate offset errors associated with the test lead resistance in
2–wire ohms measurements, follow the steps below.
1 Short the ends of the test leads together. The multimeter displays the
test lead resistance.
2 Press . The multimeter will store the test lead resistance as the
2–wire ohms null value, and enable that value to be subtracted from
subsequent measurements.
See also “Null Measurements” on page 61.
Minimizing Power Dissipation Effects
When measuring resistors designed for temperature measurements (or
other resistive devices with large temperature coefficients), be aware that
the multimeter will dissipate some power in the device–under–test.
If power dissipation is a problem, you should select the multimeter's next
higher measurement range to reduce the errors to acceptable levels. The
following table shows several examples.
Errors in High Resistance Measurements
When you are measuring large resistances, significant errors can occur due
to insulation resistance and surface cleanliness. You should take the
necessary precautions to maintain a "clean" high–resistance system. Test
leads and fixtures are susceptible to leakage due to moisture absorption in
insulating materials and "dirty" surface films. Nylon and PVC are relatively
poor insulators (10
9
W) when compared to PTFE (Teflon) insulators
(10
13
W). Leakage from nylon or PVC insulators can easily contribute a
0.1% error when measuring a 1 MW resistance in humid conditions.
Range Test Current DUT
Power at Full Scale
100 W 1 mA 100 mW
1 kW 1 mA 1 mW
10 kW 100 mA 100 mW
100 kW 10 mA10 mW
1 MW 5 mA25 mW
10 MW 500 nA 2.5 mW
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