Can an analog multimeter be replaced with a digital one?
The multimeter is without a doubt the electronic measurement tool that electricians use the most frequently, but deciding between a digital multimeter and an analog (pointer) multimeter can be difficult. for use with analog multimeters, despite claims to the contrary made by some. Many experienced, older electricians are still more accustomed to it. What distinguishes an analog multimeter from a digital multimeter? Which one should you use?
The reading display is the primary distinction between a digital multimeter and an analog multimeter. The high resolution liquid crystal display used in the digital multimeter can virtually eliminate parallax when reading data. The reading is convenient and precise, relative speaking. The analog multimeter is unmatched in this regard, but it also has some special advantages of its own, such as the ability to reflect the property changes of the measured object extremely intuitively through the instantaneous deflection of the pointer.
The intermittent measurements and displays of the digital multimeter make it difficult to track the measured electric quantity's ongoing changing process and change trend. Digital multimeters, for instance, are less practical and user-friendly than analog multimeters when it comes to examining the way capacitors charge, the way resistor resistance changes with temperature, and the way 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.
