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3
Measurement Tutorial
54
If power dissipation is a problem, you should select the
digital multimeter's next higher measurement range to
reduce the errors to acceptable levels. The following table
shows several examples:
Table 3-2 Power dissipation for various resistance ranges
Range
100 Ω
1 kΩ
10 kΩ
100 kΩ
1 MΩ
10 MΩ
100 MΩ
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
compared to Polytetrafluoroethylene (PTFE) insulators (10
Ω
). Leakage from nylon or PVC insulators can easily
contribute a 0.1% error when measuring a 1 M
in humid conditions.
Test current
1 mA
0.83 mA
100 mA
10 mA
900nA
205 nA
205 nA ||10 MΩ
DUT
power at full scale
100 mW
689 mW
100 mW
10 mW
810 nW
420 nW
35 nW
9
Ω
) when
13
Ω
resistance
U2741A User's Guide
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