Yleismittari

Yleismittari is a measuring instrument used to determine electrical quantities such as voltage, current and resistance. It combines the functions of a voltmeter, an ammeter and an ohmmeter in a single device and may include additional measurements such as capacitance, frequency, temperature, and diode or continuity testing. Modern yleismittarit are digital (digital multimeters, DMM) and typically feature a numeric display and a rotary switch to select measurement modes; many models include auto-ranging and data hold. Some models also incorporate a clamp-on current sensor.

Operation involves connecting test leads to the circuit. The device injects a small current to measure resistance; for voltage and current it presents a high-impedance input to minimize circuit disturbance. The input impedance is commonly around 1 to 10 megohms for voltage measurements. Continuity mode activates an audible buzzer when a circuit is shorted. Diode testing uses a small forward-bias current to determine conductance.

Yleismittarit are widely used by electricians, technicians and electronics hobbyists for troubleshooting, component testing and routine maintenance. They vary in accuracy, safety features and category ratings (CAT I–CAT IV) indicating appropriate voltage environments. Safety includes fuses, proper test-lead insulation and adherence to rated voltages.

Historically, multimeters evolved from volt-ohm meters used in early electronics, with digital variants becoming dominant in the late 20th century. Standards such as IEC 61010 govern safety and performance for measurement devices.