Accuracy and resolution of digital multimeter, number of bits of ADC
1. How many and a half digits are there in the multimeter?
For example, an n-and-a-half-digit multimeter can display n+1 digits, where the last n digits represent 0~9, and the highest digit can only represent 0 or 1, so it is called a half digit. The more bits, the higher the resolution (not the precision).
For example, a commonly used three-and-a-half-digit multimeter can represent the maximum value of 1999 with a resolution of 1/1000, or one thousandth; a four-and-a-half-digit multimeter can represent the maximum value of 19999 with a resolution of 1/10000 , that is, one ten-thousandth.
2. Why is it called resolution instead of precision?
Because the resolution is the minimum value that the multimeter can display, but this minimum value is not necessarily the actual measured value. The accuracy characterizes the closeness of the measured data to the actual data. This needs to be calibrated, that is, use a higher-precision instrument to measure the same value. If this value is very close to the minimum value measured by the multimeter , can explain the high accuracy of the multimeter. For example, a three-and-a-half-digit meter can accurately measure a value, while a four-and-a-half-digit meter has a large deviation from the actual value, which shows that the three-and-a-half-digit meter is more accurate than the four-and-a-half-digit meter It's still high, but the resolution is definitely less than four and a half digits.
3. The relationship between the digital multimeter and the number of digits of the ADC
The higher the number of digits of the ADC used by the multimeter, the higher the resolution of the multimeter in theory, but the multimeter also has measurement accuracy requirements, and the ADC itself has noise and errors, so the number of digits of the ADC will not be used. For example, 16bit The effective bit of the ADC may only be 14 bits, so the actual resolution of the ADC is only 1/2^14=1/16834, which is equivalent to a table with four and a half to five and a half digits. There is no strict difference between the number of bits and the resolution of the ADC. Delimitation is just a range.
