CircuVanta Lab screen Multimeter · Exterior view
LCD screen · auto rangeFunction keysRotary range switch · V, Ω, continuity, mACOM socket (black probe)
Handheld body with a display, a rotary range switch in the middle, COM, VΩ and mA inputs at the bottom, red and black probes
Palm-sized handheld body
Tools

Multimeter

In simple terms
What is this?

The stethoscope of electricity; it measures the voltage, current and resistance of a circuit.

What is it for?

Shows with a number whether a battery or a wire is good; you find the fault.

Where do you see it?

In a repairer's bag; used for battery tests and wire checks at home.

How do you spot it?

A handheld device with a display and a rotary knob in the middle; it has two probes, red and black, and three input jacks.

Caution:

Plug the probes into the right sockets; do not measure voltage at the current input, or the fuse blows and it becomes a short circuit.

Technical definition

A handheld tool that measures many quantities, mainly voltage, current and resistance. Voltage is measured in parallel with the circuit, current in series. Continuity mode tells you with a beep whether a connection is broken.

MeterV · A · Ω
ProbesCOM · VΩ
Current inputmA (400 mA fused)
Schematic symbol Same in IEC and ANSI
V

IEC 60617: the drawing style used in Türkiye and Europe.

Pins 3
1COMCommon input; the black probe always goes hereCOM
2VΩRed probe for voltage, resistance, diodes and continuityVΩ
3mADC current measurement; 400 mA fuse insidemA
Features typical
Voltage (DC/AC)
From mV to hundreds of V
Current
DC current, mA range (up to 400 mA)
Resistance
From Ω to MΩ
Continuity
Beep at low resistance
Diode test
Shows the forward voltage (≈0.6 V for silicon)
Safety
Mains measurement is outside this app's scope
Example part
Auto-ranging digital multimeter
Common mistakes
Connecting parallel to a source in current modeThe current input is almost a short circuit. Touch battery terminals with a probe in mA and the fuse blows.
Measuring resistance in a powered circuitResistance mode uses its own small voltage. On a live circuit it reads wrong and can harm the meter.
Forgetting the probe in the current inputAfter measuring current, return the red probe to VΩ; otherwise your next voltage measurement causes a short circuit.

Part health checks

Pick a part, set the range and the probes, and measure to check that it is in good shape.

Resistors

Carbon film resistorΩ · Resistance PotentiometerΩ · Resistance Metal film resistorΩ · Resistance Wire-wound resistorΩ · Resistance Cement (power) resistorΩ · Resistance SMD chip resistorΩ · Resistance Resistor network (SIP)Ω · Resistance TrimpotΩ · Resistance LDR (photoresistor)Ω · Resistance Thermistor (NTC/PTC)Ω · Resistance VaristorΩ · Resistance

Capacitors

Ceramic discF · Capacitance Aluminum electrolyticF · Capacitance MLCC (multilayer ceramic)F · Capacitance TantalumF · Capacitance Film (polyester/polypropylene)F · Capacitance SupercapacitorV⎓ · DC voltage Adjustable (trimmer) capacitorF · Capacitance

Inductors and transformers

Inductor / coil (100 µH)Ω · Resistance Transformer (24 V / 12 V, EI30)Ω · Resistance

Diodes

Rectifier diode (1N4007)→| · Diode Zener diode→| · Diode LED→| · Diode Signal diode (1N4148)→| · Diode Schottky diode→| · Diode RGB LED→| · Diode Photodiode→| · Diode Bridge diode→| · Diode

Transistors

NPN BJT (BC547)→| · Diode PNP BJT (BC557)→| · Diode N-channel MOSFET (2N7000 / IRLZ44N)→| · Diode P-channel MOSFET→| · Diode Darlington (TIP120)→| · Diode Phototransistor→| · Diode Optocoupler (PC817)→| · Diode Triac (BT136)Ω · Resistance

Power

AA batteryV⎓ · DC voltage 9 V batteryV⎓ · DC voltage Coin cell (CR2032)V⎓ · DC voltage Li-ion cell (18650)V⎓ · DC voltage Battery holderV⎓ · DC voltage Lab power supplyΩ · Resistance AC source (12 V~ 50 Hz adapter / signal generator)V~ · AC voltage Current source (constant current, bench CC mode)mA⎓ · DC current (mA)

Switches and relays

Button•))) · Continuity RelayΩ · Resistance Slide switch•))) · Continuity Toggle switch•))) · Continuity DIP switch•))) · Continuity Reed switch•))) · Continuity

Protection parts

Glass fuse (5×20 mm)•))) · Continuity Circuit breaker / MCB (C0,5, 1 pole)•))) · Continuity

Outputs

SpeakerΩ · Resistance Active buzzer•))) · Continuity Passive buzzerΩ · Resistance DC motorΩ · Resistance Servo motor•))) · Continuity 7-segment display→| · Diode Incandescent lamp (E10, 6 V 0.1 A)Ω · Resistance DC fan (5 V, 40 mm)•))) · Continuity Electric bell (6 V)Ω · Resistance

Integrated circuits

Voltage regulator (7805)Ω · Resistance 555 timerΩ · Resistance Op-amp (LM358)Ω · Resistance Logic gate (74HC00)Ω · Resistance
Find the faulty part
Where it is used
Checking battery and supply voltageMeasuring LED currentChecking the resistance valueHunting for broken wires and short circuits
Related lessons
Measuring voltage
Module 2 · Measuring with a multimetersoonMeasuring current and the fuse
Module 2 · Measuring with a multimetersoonMeasuring resistance and continuity
Module 2 · Measuring with a multimetersoon
Try it in the Lab