34410A/11A/L4411A User’s Guide 107
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 60.
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
Ω) when compared to PTFE
insulators (10
13
Ω). Leakage from nylon or PVC insulators can easily contribute a 0.1%
error when measuring a
1 MΩ resistance in humid conditions.
Range Test Current DUT
Power at Full Scale
100 Ω 1 mA 100 μW
1 kΩ 1 mA 1 mW
10 kΩ 100 μA 100 μW
100 kΩ 10 μA10 μW
1 MΩ 5 μA25 μW
10 MΩ 500 nA 2.5 μW
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