Can a digital multimeter take the place of an analog multimeter?
There is no doubt that the multimeter is the most commonly used electronic measuring instrument for electricians, but whether to choose a digital multimeter or an analog (analog) multimeter is a question~ Some people say that digital multimeters have gradually replaced analog multimeters, but many professional and experienced electricians are still more accustomed to it. Use an analog multimeter. What are the differences between digital multimeters and analog multimeters? Which one is easier to use?
First of all, the biggest difference between a digital multimeter and an analog multimeter is the reading display. The digital multimeter has a liquid crystal display with high resolution, which can fundamentally eliminate parallax when reading data, making readings relatively convenient and accurate. Analog multimeters are unmatched in this regard, but analog multimeters also have their own unique advantages, that is, they can very intuitively reflect the changes in properties of the measured object through the instantaneous deflection of the pointer.
Since the digital multimeter measures and displays in an intermittent manner, it is not convenient to observe the continuous change process of the measured power and its changing trend. For example, a digital multimeter is not as convenient and intuitive as an analog multimeter to test the charging process of a capacitor, the change of the thermistor resistance with temperature, and the changing characteristics of the photoresistor resistance with light.
In terms of working principles, analog multimeters and digital multimeters are also different. The internal structure of an analog multimeter includes a meter head, a resistor, and a battery. The meter head generally uses a magnetoelectric DC microammeter. Only when measuring resistance, the internal battery must be used. The positive electrode of the battery is connected to the black test lead, so current flows out from the black test lead and flows in from the red test lead. When measuring DC current, shunt the current by connecting a parallel resistor through gear shifting. Because 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 to the meter head, and different additional resistors are used to achieve conversion to different ranges.
A digital multimeter is composed of a function converter, A/D converter, LCD display (liquid crystal display), power supply and function/range conversion switch. The A/D converter generally uses the ICL7106 double integrating A/D converter. . ICL7106 adopts two integrations. The first time is to integrate the input analog signal V1, which is called the sampling process; the second time is to integrate the reference voltage - VEF, which is called the comparison process. The two integration processes are counted through a binary counter, converted into digital quantities, and displayed in digital form. To measure AC voltage, current, resistance, capacitance, diode forward voltage drop, transistor amplification coefficient and other electrical quantities, a corresponding converter must be added to convert the measured electrical quantity into a DC voltage signal.
There are differences in the polarity of the batteries connected inside digital multimeters and analog multimeters: 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 exactly matches the actual polarity of the diode, while the analogue meter measures the exact opposite.
In terms of use, analog multimeters are equipped with mechanical zero adjustment knobs or adjustment screws. If you find that the needle of the meter is not pointing at the mechanical zero position (i.e., the zero point of the voltage scale and the infinity of the ohm scale), you must gently use your fingers or a screwdriver to stabilize it. Slowly turn the mechanical zero point adjustment mechanism to return the hands to zero to eliminate the zero point error. The digital multimeter has an automatic zero return function, which is more convenient.
In addition, many digital multimeters now have many more functional levels compared to pointer multimeters, such as capacitance, frequency, temperature, transistor measurement gears, etc., and there are also some improvements in sensitivity, accuracy, and overload capability. In general, digital multimeters have obvious advantages, but they cannot completely replace analog multimeters. They have their own advantages in different measurement scenarios, and you need to choose according to your actual measurement needs.
