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Basic Techniques for Accurate Resistance Measurement
By: CAS Dataloggers
At CAS DataLoggers we often receive calls from users working in resistance measurement applications, for example using string pots to measure displacement, measuring thermistors or RTDs for temperature, measuring the resistance on test samples, and many more applications.
Figure 1. Forcing a Know Current
You run 2 wires one to each side of the resistor, then force the current through both sets of leads. However, this creates an error in your measurements because the voltage measured at the end of the leads isn't the same as the voltage across the resistor, as it also includes the voltage drop across the wires between the meter and DUT caused by the current flowing through these wires.
Figure 2. Sourcing Voltage Through a Known Resistor
For this technique to work well, the value of the test resistance should be similar to the value of the unknown resistance (within 1 to 2 orders of magnitude). Here again, your voltmeter must have good accuracy, otherwise, it'll introduce an error into your measurements.
At less than 10,000 ohms, you can use the techniques given above for the low resistance ranges—when you get to 100 ohms and lower, you'll certainly need it to obtain accurate readings. Likewise, above 100,000 ohms it's best to use the force voltage technique described above for high ohm ranges.
For more information on resistance measurement or resistance data loggers, or to find the ideal solution for your application-