A multimeter is an electronic device that measures electrical properties such as DC or AC voltage, resistance and current. This device combines all the three functions of an ohmmeter, a voltmeter and an ammeter in one measuring instrument.
There are two main types of multimeters: analogue multimeters and digital multimeters. Digital multimeters have LCD screens that display direct decimal readings, while analogue multimeters display measurements through scales with moving bars and their results must be interpreted.
As an ammeter, a multimeter can measure the current flowing through a circuit by interrupting the circuit. This device is usually connected in series to enable all the current of the circuit to flow through the sensors of the ammeter.
When used as a voltmeter, a multimeter measures the amount of DC or AC voltage flowing through a given circuit. To test the voltage of a machine, you should choose DC or AC, choose an upper limit on the voltage and then plug the machine into the multimeter, without breaking the complete circuit. You can confirm whether the machine is functioning normally by comparing the readout to the data provided in the manual of the machine.
When used as an ohmmeter, the multimeter measures resistance in a circuit and gives its readings in ohms.