Measurement Methods and AC Frequency Response of Multimeters
The digital multimeter can not only measure DC voltage (DCV), AC voltage (ACV), DC current (DCA), AC current (ACA), resistance (Ω), diode forward voltage drop (VF), transistor emitter current amplification coefficient (hrg), but also measure capacitance (C), conductivity (ns), temperature (T), frequency (f), and add a buzzer range (BZ) to check line continuity Low power method for measuring resistance range (L0 Ω). Some instruments also have functions such as inductance level, signal level, AC/DC automatic conversion, and capacitance level automatic range conversion.
Generally speaking, the measurement method of a multimeter is mainly for AC signal measurement. It is well-known that there are many types and complex situations of AC signals, and with the change of AC signal frequency, various frequency responses occur, which affects the measurement of the multimeter. There are generally two methods for measuring AC signals with a multimeter: average value and true RMS measurement. The average measurement is generally for pure sine waves, which uses the method of estimating the average to measure AC signals, while for non sine wave signals, there will be significant errors.
At the same time, if there is harmonic interference in the sine wave signal, the measurement error will also have a significant change. The true effective value measurement is calculated by multiplying the instantaneous peak of the waveform by 0.707 to calculate the current and voltage, ensuring accurate readings in distortion and noise systems. If you need to detect ordinary digital data signals, measuring with an average multimeter will not achieve the true measurement effect. At the same time, the frequency response of communication signals is also crucial, some can reach up to 100KHz.
The Development Trend of Digital Multimeters
Integration: The handheld digital multimeter adopts a single chip A/D converter, and the peripheral circuit is relatively simple, requiring only a small amount of auxiliary chips and components. With the continuous emergence of specialized chips for single chip digital multimeters, using a single IC can form a fully functional automatic range digital multimeter, creating favorable conditions for simplifying design and reducing costs.
Low power consumption: New digital multimeters generally use CMOS large-scale integrated circuit A/D converters, resulting in low overall power consumption.
