Usage of Multimeter Range Selector Switch
Modern multimeters have many new functions, especially digital multimeters. They can measure capacitance, transistor current gain, diode voltage drop and more. There is even a voice-output digital multimeter that announces measurement results aloud. There are many classic models of digital multimeters, such as DT830C, DT890D, etc. The suffix indicates differences in functions. The DT830C can be purchased for around more than 30 yuan per unit, which is quite economical.
The most prominent feature of a multimeter is its range selector switch, which is used to switch between various measurement functions. Basically:
A− stands for DC current measurement; there are usually several milliampere and ampere sub-ranges.
V− stands for DC voltage measurement. Higher-grade multimeters include millivolt ranges, and the voltage function also has multiple gears.
V~ is for AC voltage measurement.
A~ is for AC current measurement.
The Ω (ohm) range is used for resistance measurement. For analog multimeters, resistance zero adjustment must be performed every time the resistance range is changed. Zero adjustment means shorting the red and black test leads together, then rotating the zero-adjust knob to align the pointer with the zero mark. hFE is used to measure the current amplification factor of transistors. Simply insert the three pins of the transistor into the corresponding jacks on the multimeter panel to read the hFE value. Note that PNP and NPN transistors are different.
The MF30 multimeter is used below as an example to explain multimeter readings. The first scale line indicates resistance values. The far left represents infinite resistance and the far right is zero; the graduations in the middle are non-linear. Resistance ranges include R×1, R×10, R×100, R×1K and R×10K. Multiply the reading on the scale by the multiplier factor to get the actual resistance value in ohms.
Example: When measuring a resistor with the R×100 range and the pointer points to "10", the resistance value is 10 × 100 = 1000Ω, namely 1kΩ.
The second scale line is shared by the 500V voltage range and the 500mA current range. It should be noted that the reading principle for voltage and current ranges differs from that of the resistance range. For example, the 5V range can only measure voltages below 5V, and the 500mA range can only measure currents below 500mA. Exceeding the measuring range will damage the multimeter.
