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Electrical resistance plays a particularly necessary function within the circuitry of electronic devices. Such units might malfunction if the resistance of their circuitry diverges from the proper level. However, electricity will not be visible. A specialized measuring instrument is critical with a view to investigate whether or not a circuit has the proper resistance.

An instrument resembling a tester is necessary in order to measure resistance, but how is such measurement carried out? This page provides a detailed introduction to how a tester or multimeter can be used to measure resistance.

How is resistance measured?

Resistance is measured using an instrument similar to an analog multimeter or digital multimeter. Each types of instrument can measure not only resistance, but in addition present, voltage, and different parameters, to allow them to be utilized in quite a lot of situations.

Nonetheless, resistance measurement doesn’t contain measuring the circuit’s resistance worth itself. Instead, resistance is calculated by measuring the current and voltage utilized to the circuit. When a current is applied to the circuit under measurement, the circuit (resistance) exhibits a voltage (or more exactly, a voltage drop). Resistance could be calculated by measuring the present and voltage utilizing Ohm’s Law.

As a result, a circuit’s resistance value may be determined if the current and voltage measured values are known. Analog multimeters and digital multimeters employ the measurement principle of Ohm’s Law to measure resistance.

Resistance measurement with an analog tester

When measuring resistance with an analog multimeter, switch off energy to the circuit under measurement. Plug the red test lead into the positive input terminal with the “+” mark and the black test lead into the COM input terminal. Switch the instrument to Ω mode and set the range button as appropriate based on the circuit’s anticipated resistance.

Quick the black and red test pins and set the needle to zero Ω using the 0 Ω adjustment knob. Then place the red and black test pins involved with both ends of the circuit under measurement and read the value indicated by the meter.

Keep in mind that making use of a voltage to the test leads while the instrument is set to resistance mode could damage the tester. Additionally, if you are unable to perform zero Ω correction, the analog multimeter’s battery could also be low. When you encounter this challenge, check the battery’s voltage.

Resistance measurement with a digital multimeter

Generally, resistance is measured with a digital multimeter in the identical method as with an analog multimeter, and it’s a quite simple process. The only distinction is that the worth is indicated digitally instead of by an analog needle; otherwise, the essential method is usually the same. Nevertheless, digital multimeters assist measurement methods:

Two-terminal measurement

Four-terminal measurement

In most cases, when measuring resistance with a digital multimeter, you’ll use the two-terminal measurement method. This methodology applies a relentless present and measures the resistance worth using the instrument’s voltmeter. This technique is the same as that utilized by analog multimeters. Nevertheless, two-terminal measurement has the disadvantage of yielding resistance values that include the wiring between the instrument and the circuit under measurement.

To reduce the effects of that additional resistance, the test leads are shorted previous to measurement to zero-adjust the resistance value. However, this technique can’t completely get rid of the effects. Four-terminal measurement was created to address this shortcoming. 4-terminal measurement uses four test leads and separate voltmeter and ammeter circuits.

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