Principle of mechanical pointer multimeter - Solutions - Huaqiang Electronic Network

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

GW MB10F 0.8A 1000V rectifier bridge

The multimeter is one of the most essential tools in electronics, used to measure various electrical parameters like voltage, current, and resistance. Its core component is a sensitive magnetic-electric DC ammeter, also known as a micro-ampere meter. This device can detect small currents and provide a visual reading on its scale. However, it's not designed to handle large currents directly, so additional components are used to extend its measurement capabilities. When measuring **DC current**, the multimeter uses a shunt resistor connected in parallel with the meter head. This allows most of the current to bypass the meter, while a small portion flows through it, enabling accurate readings without damaging the sensitive instrument. By adjusting the value of the shunt resistor, different current ranges can be measured. For **DC voltage**, a multiplier resistor is added in series with the meter head. This resistor limits the current flowing through the meter by increasing the total resistance, allowing the multimeter to measure higher voltages safely. Changing the resistor value adjusts the voltage range accordingly. When measuring **AC voltage**, the process is slightly more complex. Since the meter head only responds to DC, an AC signal must first be converted into a DC signal using a rectifier circuit. Typically, a half-wave rectifier is used, which converts the alternating current into a pulsating direct current. This DC signal is then measured using the same method as for DC voltage, with the range adjusted via a multiplier resistor. To measure **resistance**, the multimeter uses a combination of resistors and an internal battery. A known voltage is applied across the resistor being tested, and the resulting current is measured. Based on Ohm’s Law (V = IR), the resistance value is calculated. A shunt resistor is used to adjust the range, allowing the multimeter to measure both high and low resistance values effectively.