Multimeter measurement methods and AC frequency response
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), and transistor emitter current amplification coefficient ( hrg), it can also measure capacitance (C), conductance (ns), temperature (T), frequency (f), and adds a buzzer level (BZ) for checking line continuity and low-power method for measuring resistance. gear (L0Ω). Some instruments also have automatic conversion functions for inductance gear, signal gear, AC/DC, and automatic range conversion for capacitance gear.
Generally speaking, the measurement method of a multimeter is mainly for AC signal measurement. Everyone knows that there are many types of AC signals and various complex situations, and as the frequency of the AC signal changes, various frequency responses appear, which affects the measurement of the multimeter. There are generally two methods for measuring AC signals with a multimeter: average value and true effective value measurement. Average measurement is generally for pure sine waves. It uses the estimated average method to measure AC signals. However, larger errors will occur for non-sinusoidal signals.
At the same time, if harmonic interference occurs in the sine wave signal, the measurement error will also change greatly. The true RMS measurement uses the instantaneous peak value of the waveform multiplied by 0.707 to calculate the current and voltage to ensure that the current and voltage are correct in the distortion and noise system. accurate readings. In this way, if you need to detect ordinary digital signals, measuring with an averaging multimeter will not achieve the true measurement effect. At the same time, the frequency response of AC signals is also very important, and some can be as high as 100KHz.
Development Trends of Digital Multimeters
Integration: The handheld digital multimeter uses a single-chip A/D converter, and the peripheral circuit is relatively simple, requiring only a few auxiliary chips and components. With the continuous advent of single-chip digital multimeter dedicated chips, a relatively complete automatic range digital multimeter can be constructed using one IC, 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, and the overall power consumption is very low.
