Measurements with a multimeter and AC frequency response
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 current amplification factor of the emitter (hrg), but also measure the capacitance (C), conductivity (ns), temperature (T), frequency (f), and added to check the line off the Buzzer file (BZ), low-power method of measuring resistance file (L0Ω). Some meters also have an inductive file, signal file, AC/DC automatic conversion function, capacitance file automatic conversion range function.
Generally speaking, the measurement method of the multimeter is mainly for the measurement of AC signals, we all know that many types of AC signals and a variety of complexities, and along with the change in the frequency of AC signals, there are a variety of frequency response, affecting the measurement of the multimeter. The measurement of AC signal by multimeter generally has two methods: average value and true RMS measurement. Mean value measurement is generally for pure sine wave, which uses the estimation of the average method to measure the AC signal, while the non-sine wave signal will have a large error.
Meanwhile, if harmonic interference occurs in the sine wave signal, the measurement error will also change greatly, while the True RMS measurement, which uses the instantaneous peak value of the waveform multiplied by 0.707 to calculate the current and voltage, ensures accurate readings in distorted and noisy systems. This means that if you need to test an ordinary digital data signal, you won't get a true measurement with an average multimeter. At the same time the frequency response of the AC signal is also relevant, some can be as high as 100KHz.
The development trend of digital multimeter
Integration: handheld digital multimeter using a single chip A/D converter, the peripheral circuit is relatively simple, only a small number of auxiliary chips and components. With the continuous introduction of monolithic digital multimeter special chip, the use of a piece of IC can constitute a relatively complete function of the automatic range of digital multimeter, to simplify the design and reduce costs to create favorable conditions.
Low power consumption: the new digital multimeter generally adopts CMOS large-scale integrated circuit A/D converter, the whole machine power consumption is very low.
