Readings and accuracy of 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 meter: one is that it can display all the digits from 0-9 in the integer digits; 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 meter 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. In the same situation, 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 multimeter. The relationship between the two is close. Generally speaking, the higher the number of display digits, the higher the accuracy of the multimeter, 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 due to people's habits and the convenience of the traditional call, generally expressed in the bit display.
For example: 3,000-bit count display, indicating 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 is obvious to see that 3,000-bit display is more than 1,000-bit display with 1 more decimal digit: this is an order of magnitude higher resolution, which is in the highly sensitive microelectronic signals debugging and testing, the high-sensitivity 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 the number in front as the denominator of the fraction, and then subtract the number from 1 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 / analog hybrid meter, digital / analog map double display of the instrument, the universal oscilloscope (digital multimeter, digital storage oscilloscope, and other kinetic energy set in one).
