Introduction on How to Choose Digital Multimeters
① Analog meters have poor reading accuracy, yet the deflection of the pointer is intuitive. The speed and amplitude of pointer swing can sometimes objectively reflect the magnitude of the measured quantity (e.g., capturing minor jitter when measuring data transmission on a TV data bus (SDL)). Digital meters provide direct readouts, but fluctuating numerals appear erratic and are difficult to observe.
② Analog meters generally contain two batteries: a 1.5 V low‑voltage battery and a 9 V or 15 V high‑voltage battery. The black probe is the positive terminal relative to the red probe. Digital meters usually use a single 6 V or 9 V battery. In the resistance range, the probe output current of an analog meter is much higher than that of a digital meter. The R×1Ω range can produce a loud "click" sound from a speaker, and the R×10kΩ range can even light up a light‑emitting diode (LED).
③ For voltage measurement ranges, analog meters feature lower internal resistance and relatively lower measurement accuracy. They may fail to obtain accurate readings in scenarios with high voltage and tiny current, as their internal resistance will load the circuit under test (for instance, readings will be much lower than the true value when measuring the accelerating electrode voltage of a TV picture tube). Digital meters have very high internal resistance in voltage ranges, at least in the megaohm range, imposing minimal impact on the circuit under test. However, their extremely high input impedance makes them susceptible to induced voltage; readings may be false under strong electromagnetic interference.
④ In summary, analog meters are suitable for measuring analog circuits with relatively high current and high voltage, such as televisions and audio power amplifiers. Digital meters are preferred for low‑voltage, low‑current digital circuit measurements, such as pagers and mobile phones. This is not absolute; analog or digital meters may be selected according to actual conditions.
