Display units and accuracy of the multimeters
The number of display digits of a digital multimeter is usually 3 1/2 digits to 8 1/2 digits. There are two principles for determining the number of display digits of a digital instrument: one is that the number of digits that can display all the digits from 0-9 is the integer number; the other is that the value of the fractional digit is the highest digit in the maximum display value as the numerator, with the full scale count value of 2,000, which indicates that the instrument has three integer digits, while the numerator of the fractional digit is 1, and the denominator is 2, so it is called 3 1/2 digits, pronounced as "three and a half", and its highest digit can only display 0 or 1 (0 is usually not displayed). Bit, read as "three and a half", its highest bit can only display 0 or 1 (0 is usually not displayed).3 2/3 bit (read as "three and two-thirds bit") digital multimeter's highest bit can only display 0 ~ 2 of the number, so the maximum display value of ± 2999. In the same case, it is more than 3 2/3 bit (read as "three and two-thirds bit") digital multimeter's highest bit can only display 0 ~ 2 of the number, so the maximum display value for ± 2999. Under the same circumstances, it is 50% higher than the limit of 3 1/2 digital multimeter, especially in the measurement of 380V AC voltage is very valuable.
The number of display digits and accuracy are the two most basic and important indicators of a multimeter. The relationship between the two is close, generally speaking, the higher the display digit of the multimeter, the higher the accuracy, and vice versa. However, due to the measurement principle and the quality standard of each manufacturer is not the same, in the same digit, some multimeters have high precision, some are poor. For example: the same 41/2 multimeter, some models have an accuracy of up to 0.025% while others have only 0.8%. There are two ways of displaying the number of digits: count display and digit display. Counting display is the actual expression of the multimeter display bit range, but because of people's habits and the convenience of the traditional call, generally expressed in the bit display.
For example: 3,000-bit count display, that the highest display value of the multimeter can be up to 3,999 while 1,000-bit count display can only be up to 1,999, when measuring 220VAC voltage, it can be clearly seen that 3,000-bit display than 1,000-bit display more than 1 decimal digit display: so that the resolution of an order of magnitude higher, which in the highly sensitive microelectronic signals in the debugging and testing, the high sensitivity of the multimeter will happen! This is an order of magnitude higher resolution. At the same time, the counting display and the digit display can be converted: first count how many zeros in the counting display digits, and then take the previous number as the denominator of the fraction, and then subtract 1 from the number to become the numerator, which becomes the digit display. For example, for a 3000-bit count, the number of digits is 32/3. Existing handheld multimeters have a bit count of 500,000 bits.
Digital multimeter according to the range conversion method to classify, can be divided into three types: manual range (MAN RANGZ), automatic range (AUTO RANGZ), automatic / manual range (AUTO / MAN RANGZ).
According to the function, use and price of different, digital multimeter can be roughly divided into 9 categories: low-grade digital multimeter (also known as popular digital multimeter), mid-range digital multimeter, medium/high-grade digital multimeter, digital / analogue hybrid instrument, digital / analogue map double display of the instrument, universal oscilloscope (digital multimeter, digital storage oscilloscope and other kinetic energy in one).
