Users manual
ET3260 and ET3260A
6 1/2 Digit Multimeter
42
5.1.5 Resistance measurement considerations
Multimeter provides two resistance measurement methods, that is, 2-wire and 4-wire resistance,
where test current goes out from input HI terminal, and goes through resistor under test. In the
2-wire resistance measurement method, the voltage drop on resistor under test is internally
sensed to multimeter, therefore, the measurement includes test lead resistance at the same time.
In the 4-wire resistance measurement method, adopt independent
Sense
connection, and since
the current does not go through sense lead, resistance in these leads will not cause measurement
error.
The DC voltage measurement error mentioned in former part of this chapter is also suitable for
resistance measurement, and error source peculiar to other resistance measurements will be
discussed in latter part.
4-wire resistance measurement
4-wire resistance method is the most accurate method to measure low resistance, which can
automatically eliminate resistance of test lead and contact resistance and is generally used for
automation test under the situation where there are resistance, long-cable or plentiful connections
or switches between multimeter and equipment under test. The connecting figure is as shown in
the following.
Eliminate test lead resistance errors in 2-wire resistance measurement
Operate step by step to eliminate offset error existing in 2-wire resistance measurement and
related to test lead resistance.
1. Short the two terminals of test leads together and multimeter displays test lead resistance.
2. Start
Relative measurement
function, and multimeter saves the test lead resistance as the
zero-value of 2-wire resistance and subtracts the value from future measurement result.
Minimize power consumption influence
When measure resistor is used in temperature measurement (or resistance equipment with large
temperature parameters), you are required to pay attention to that multimeter will consume
certain amount of power of the equipment under test. If the power consumption has much
influence on measurement, you should select multimeter’s next higher measurement range to
reduce the error to an acceptable level.
5.2 AC Measurement Considerations
5.2.1 True virtual value AC measurement
