Best Practices for Measuring Resistance with NI Digital Multimeter

The wire configuration you should use for your NI DMM depends on the target measurement. If the target measurement is more than 100 kΩ, use a 2-wire configuration. If the target measurement is less than 100 kΩ, use a 4-wire configuration. 

2-Wire Configuration

The 2-wire method is commonly used as it is the simplest and most straightforward method. In 2-wire, you can get accurate measurements above 100 kΩ relatively easily.

• Learn more about 2-wire resistance measurements
• To see a diagram for how your NI DMM should be configured for 2-wire measurements, visit the NI Digital Multimeters Help and select your hardware model, then select the Front Panel Connections topic.

4-Wire Configuration

For precision measurements with resistances below 100 kΩ, 4-wire works more reliably and conveniently than 2-wire. A 4-wire configuration requires 4-wire switching and more cabling; however, you may decide the tradeoff is acceptable, depending on the accuracy versus complexity requirements of your system.

• Learn more about 4-wire resistance measurements
• To see a diagram for how your NI DMM should be configured for 4-wire measurements, visit the NI Digital Multimeters Help and select your hardware model, then select the Front Panel Connections topic.

Offset Compensated Ohms is a NI-DMM driver feature provided for eliminating thermal EMFs or offset voltages in a resistance test system. Offset Compensated Ohms applies to both 2-wire and 4-wire resistance.

• Learn more about Offset Compensated Ohms and when it should be used
• Learn how to configure Offset Compensated Ohms

Offset nulling measures the corresponding zero reading in a measurement path and subtracts the value from subsequent samples.

Learn how to perform offset nulling

When measuring resistance in a system, it is important to consider the effects of cable resistance. It is also important to notice that interactions between scanning multiple resistances and system cabling can present time-dependent problems.

Learn more about system considerations for resistance measurements

Electrostatic noise pickup becomes a major concern when measuring high resistances. To prevent problems with noise pickup, proper shielding is critical when measuring resistances greater than 100 kΩ.

Learn more about optimizing for high-resistance measurements

A commonly overlooked source of noise is the source noise. The inherent noise generated by a non-ideal resistor is called Johnson noise. To get a meaningful measurement with resistances above 10 MΩ, you must have good shielding, including the resistor under test.

• Learn more about measuring on the 100 MΩ range
• Learn more about Johnson noise of resistors
   

The Johnson noise of typical high MΩ resistors is listed below in ppm of reading, assuming a bandwidth of 10 Hz (roughly equivalent to a 100 ms aperture time).

¹Represents the "ideal" noise on the best range for that resistance (ohms) measurement due to the Johnson noise of the resistor. Actual noise may be higher, due to environment, poor shielding, and so on.

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