Can a multimeter replace an analog multimeter?
Undoubtedly, the multimeter can be said to be the most commonly used electronic measuring instrument for electricians, but it is a problem to choose a digital multimeter or an analog (pointer) multimeter~ Some people say that digital multimeters have gradually replaced analog multimeters, but many professional old electricians are still more used to it. for use with analog multimeters. What is the difference between a digital multimeter and an analog multimeter? Which one is better to use?
First of all, the biggest difference between a digital multimeter and an analog multimeter is the reading display. The digital multimeter is a liquid crystal display with high resolution, which can fundamentally eliminate the parallax when reading data. Relatively speaking, the reading is convenient and accurate. In this respect, the analog multimeter is incomparable, but the analog multimeter also has its own unique advantages, that is, it can reflect the property changes of the measured object very intuitively through the instantaneous deflection of the pointer.
Since the digital multimeter measures and displays intermittently, it is not convenient to observe the continuous change process of the measured electric quantity and its change trend. For example, digital multimeters are not as convenient and intuitive as analog multimeters for checking the charging process of capacitors, the law of thermistor resistance changes with temperature, and observing the characteristics of photoresistor resistance changes with light.
In terms of working principle, the analog multimeter and the digital multimeter are also different. The internal structure of the analog multimeter includes a meter head, a resistor, and a battery. The meter head generally adopts a magnetoelectric DC microammeter. Only when measuring resistance, use its internal battery. The positive pole of the battery is connected to the black test lead, so the current flows out from the black test lead and the red test lead flows in. When measuring DC current, shunt the current by connecting parallel resistors by shifting gears. Because the full-bias current of the meter head is very small, the shunt resistors are used to expand the range. When measuring DC voltage, connect resistors in series on the meter head, and realize the conversion of different ranges through different additional resistors.
A digital multimeter is composed of a function converter, an A/D converter, an LCD display (liquid crystal display), a power supply, and a function/range conversion switch, among which the A/D converter generally adopts the ICL7106 dual-integral A/D converter . The ICL7106 uses two integrations, the first integration of the input analog signal V1 is called the sampling process; the second integration of the reference voltage - VEF is called the comparison process. The two integration processes are counted by a binary counter, converted into digital quantities, and displayed in digital form. To measure electricity such as AC voltage, current, resistance, capacitance, diode forward voltage drop, and transistor amplification factor, a corresponding converter must be added to convert the measured electricity into a DC voltage signal.
The polarity of the battery connected inside the digital multimeter and the pointer multimeter is different: the digital red test lead is connected to the positive pole of the battery, the black test lead is connected to the negative pole, and the analog multimeter is just the opposite. The diode measured by the digital meter is exactly in line with the actual polarity of the diode, while the pointer type is just the opposite.
In use, analog multimeters are equipped with mechanical zero point adjustment knobs or adjustment screws. If you find that the hands are not pointing to the mechanical zero position (that is, the zero point of the voltage scale and the infinity of the ohm scale), you must use your fingers or a screwdriver. Slowly turn the mechanical zero point adjustment mechanism to return the watch hands to zero to eliminate zero point errors. The digital multimeter has an automatic zero return function, which is more convenient.
In addition, compared with the pointer multimeter, many digital multimeters now have a lot of function gears, such as capacitance, frequency, temperature, triode measurement gear, etc., and there are also some improvements in sensitivity, accuracy, and overload capacity. In general, digital multimeters have obvious advantages, but they cannot completely replace analog multimeters. There are still advantages and disadvantages in different measurement scenarios, and you need to choose according to your actual measurement needs.
