PlantFlow 3D › Guides › How to use a multimeter: voltage, continuity and resistance
How to use a multimeter: voltage, continuity and resistance
A practical guide to measuring AC voltage, testing continuity with the buzzer, reading coil and winding resistance, and using a clamp meter safely in control panels.
Choose the right range first
A digital multimeter has separate ranges for AC voltage (V~), DC voltage (V⎓), resistance (Ω) and continuity (the buzzer symbol). Most control circuits are 230 V AC or 24 V DC. Measuring an AC circuit on the DC range shows a wrong, small value, so always check the range before touching the probes on.
Black probe goes in COM, red probe in V/Ω. For current, a clamp meter is safer than breaking the circuit: close the jaws around one single conductor, not around a whole cable.
Live tests: following the voltage
With the supply on, put the black probe on neutral (or the control N) and move the red probe along the circuit from the supply towards the load: after the MCB, after the overload contact, after the STOP button and so on. The voltage is present up to the open point and disappears after it. This is the fastest way to find an open contact or a broken wire.
Reading 0 V across a closed contact is normal, because both sides are at the same potential. Reading 230 V across a contact means it is open.
Dead tests: continuity and resistance
Continuity and resistance must only be measured on a dead circuit. Switch off, lock off and prove dead with the voltage range first. A meter on Ω connected to a live circuit can be damaged and gives meaningless readings.
Typical readings: a good wire or a closed contact beeps and reads below 1 Ω; a contactor coil reads a few hundred ohms; a motor winding reads a few ohms and all three windings should be equal; an open circuit shows OL.
Common mistakes
Testing for “no voltage” without first proving the meter on a known live source; measuring resistance with parallel paths still connected; and holding the probes by the metal tips. Use a meter rated CAT III for distribution and motor panels.
Try it yourself
The PlantFlow multimeter works on the wiring view: tap two terminal screws to measure. Try the Ω range on a live circuit and see the LIVE warning, then switch off and hear the continuity buzzer.
Open the PlantFlow 3D simulator →Safety: this guide explains principles for learning. Real installations must follow the applicable codes, the equipment manufacturer's instructions and the approval of a competent, qualified person. Isolate, lock off and prove dead before touching any circuit.