The meaning of the digits of a digital multimeter
There are two principles for determining the number of digits displayed on a digital instrument: one is that all digits from 0 to 9 can be displayed as integer digits; The second is that the value of the fractional digits is based on the highest digit in the maximum displayed value as the numerator, and the highest digit at full scale as the denominator
For example, the maximum displayed value of a digital multimeter is ± 1999, and the full-scale count value is 2000. This indicates that the instrument has 3 integer digits, and the numerator of the decimal place is l and the denominator is 2, so it is called 3 1/2 digit, pronounced as "three and a half digits", and its highest digit can only display 0 or 1 (0 is usually not displayed).
The highest digit of a 3 2/3 digit (pronounced as "3 and 2/3 digits") digital multimeter can only display numbers from 0 to 2, so the maximum displayed value is ± 2999. In the same situation, it is 50% higher than the limit of 3 1/2 bit DMM, which is only ± 1999.
It should be pointed out that some people still refer to the 3 2/3 position instrument as the 3 1/2 position instrument, but it must be indicated that its limit has been expanded by 50% to avoid confusion between the two.
The highest position of a 3 3/4 digit digital multimeter can display numbers from 0 to 3, so the maximum displayed value is ± 3999, which is twice the limit of a 3 1/2 digit meter. There are many advantages to using a 3 3 3/4 digit digital multimeter to measure grid voltage. For example, the second highest AC voltage range of a typical 3 1/2 digit DMM is 200V. If you want to measure 220V or 380V grid voltage, you must choose the * high AC voltage range (usually 700V~750V range), which has a resolution of only 1V. In contrast, the second highest ACV range of a 3 3/4 digit DMM is 400V, which is most suitable for measuring power frequency grid voltage. It is neither under range nor over range, and its measurement accuracy is better than the 700V range mentioned above. The resolution can be increased by 10 times, reaching 0.1V, which is the same as the 700V range resolution of the 4 1/2 DMM.
Universal digital multimeters generally belong to 3 1/2 digit instruments. There are two types of 4 1/2 digit multimeters: handheld and desktop. Most instruments with 5 1/2 digits or more belong to desktop intelligent digital multimeters.
