How to measure resistance using the resistance range of a digital multimeter
In electrical barrier measurement resistance, resistance values vary widely, from a few milliohms (mΩ) of contact resistance to billions of ohms of insulation resistance.
Many digital multimeters measure resistance as small as 0.1 ohm, and some measurements can be as high as 300 megohms (300,000,000ohms).
For extremely large resistance, the Fluke multimeter will display "OL", indicating that the resistance being measured exceeds the range. When measuring an open circuit, "OL" will be displayed.
The resistance must be measured with the circuit power turned off, otherwise the meter or circuit board will be damaged. Some digital multimeters provide protection when a voltage signal is mistakenly connected in resistive mode. Different models of digital multimeters have different protection capabilities.
When making accurate measurements of low resistance, the resistance of the measuring lead must be subtracted from the measured value. Typical test lead resistances range from 0.2Ω to 0.5Ω. If the resistance of the test lead is greater than 1Ω, the test lead needs to be replaced.
A digital multimeter can measure resistance on a circuit board that is isolated by a diode or semiconductor if it supplies a DC voltage of less than 0.6V to the resistance being measured. This allows testing without removing the resistor.
Steps to test resistance online:
1. Turn off the circuit power;
2. Select electrical blocking;
3. Insert the black test lead into the COM jack and the red test lead into the resistance test jack;
4. Connect the test lead probes to both ends of the component or circuit under test;
5. Look at the reading and pay attention to whether the unit is ohms (Ω), kiloohms (kΩ), or megaohms (MΩ).
Note: 1,000Ω=1KΩ, 1,000,000Ω=1MΩ.
NOTE: Turn off power while testing resistors.
