Criteria for Selecting Digital Multimeters
The resolution of a digital multimeter is an important indicator, just like when you want to measure lengths less than 1 millimeter, you definitely won't use a ruler with centimeters as the unit of measurement; Or if the temperature is 98.6 ° F, measuring with a thermometer marked only with integers is not useful. You need a thermometer with a resolution of 0.1 ° F.
A table with 3 and a half digits, where the last three digits can display all three digits from 0 to 9, and the first digit only displays one and a half digits (showing 1 or not). This means that a table with 3 and a half digits can achieve a resolution of 1999 words; A 4.5 bit digital multimeter can achieve a resolution of 19999 words. Describing the resolution of a numerical table with words is better than describing it with digits. The resolution of the current 3.5-digit multimeter has been increased to 3200 or 4000 words. A 3200 word digital multimeter provides better resolution for certain measurements. For example, a 1999 word meter cannot display 0.1V when measuring voltages greater than 200V. However, a 3200 word digital multimeter can still display 0.1V when measuring voltages of 320V. When the measured voltage is higher than 320V and a resolution of 0.1V is required, a more expensive 20000 word digital multimeter is needed.
Accuracy: refers to the maximum allowable error that occurs in a specific usage environment. In other words, accuracy is used to indicate the degree of closeness between the measured value of a digital multimeter and the actual value of the measured signal. For a digital multimeter, accuracy is usually expressed as a percentage of the reading. For example, a reading accuracy of 1% means that when a digital multimeter displays 100.0V, the actual voltage may be between 99.0V and 101.0V. In the detailed manual, there may be specific numerical values added to the basic precision, which means the number of words to be added to the right end of the display for transformation. In the previous example, the accuracy may be marked as ± (1%+2). Therefore, if the reading on the multimeter is 100.0V, the actual voltage will be between 98.8V and 101.2V. The accuracy of an analog meter (or pointer multimeter) is calculated based on the full range error, rather than the displayed reading. The typical accuracy of a pointer multimeter is ± 2% or ± 3% of the full range. The typical basic accuracy of a digital multimeter is between ± (0.7%+1) and ± (0.1%+1) of the reading, or even higher.
