Can a digital multimeter replace an analog one
Undoubtedly, a multimeter can be said to be the most commonly used electronic measuring instrument for electricians, but choosing a digital multimeter or an analog (pointer) multimeter is a question. Some people say that digital multimeters have gradually replaced analog multimeters, but many professional electricians are still more accustomed to using analog multimeters. What are the differences between a digital multimeter and an analog multimeter? Which one is better to use?
The biggest difference between a digital multimeter and an analog multimeter is the display of readings. A digital multimeter is a liquid crystal display with high resolution, which can fundamentally eliminate the parallax when reading data, making readings relatively convenient and accurate. In this regard, analog multimeters cannot compare, but they also have their own unique advantages, which are that they can intuitively reflect the changes in the properties of the measured object through the instantaneous deflection of the pointer.
Due to the fact that digital multimeters measure and display electricity in an intermittent manner, it is not convenient to observe the continuous changes and trends of the measured electricity. For example, a digital multimeter is not as convenient and intuitive as an analog multimeter to test the charging process of capacitors, the variation of thermistor resistance with temperature, and the observation of the variation characteristics of photoresistor resistance with light.
In terms of working principle, analog multimeters and digital multimeters are also different. The internal structure of analog multimeters includes a meter head, a resistor, and a battery. The meter head generally uses a magneto electric DC microampere meter. When measuring resistance, the internal battery should be used, and the positive terminal of the battery should be connected to the black probe, so the current flows out from the black probe and into the red probe. When measuring DC current, a shunt resistor is connected by shifting gears to divert the current. Since the full bias current of the meter is very small, a shunt resistor is used to expand the range. When measuring DC voltage, a resistor is connected in series with the meter head, and different additional resistors are used to achieve conversion between different ranges.
A digital multimeter is composed of a function converter, an A/D converter, an LCD display, a power supply, and a function/range conversion switch, among which the A/D converter generally uses an ICL7106 dual integration type A/D converter. ICL7106 adopts two integrals, the first of which integrates the input analog signal V1, known as the sampling process; The second integration of the reference voltage - VEF integration is called the comparison process. Count two integration processes using a binary counter, convert them into digital quantities, and display them in digital form. To measure AC voltage, current, resistance, capacitance, diode forward voltage drop, transistor amplification factor, and other electrical quantities, corresponding converters must be added to convert the measured electrical quantities into DC voltage signals.
