Digital Multimeter Accuracy (Precision)
The accuracy of a digital multimeter is a combination of systematic and random errors in the measurement results. It indicates the degree of agreement between the measured value and the true value, and also reflects the size of the measurement error. Generally speaking, the higher the accuracy, the smaller the measurement error, and vice versa.
Accuracy can be expressed in three ways, as follows:
Accuracy = ±(a % RDG + b % FS) (2.2.1)
Accuracy = ±(a % RDG + n words) (2.2.2)
Accuracy = ±(a % RDG + b % FS + n words) (2.2.3)
In formula (2.2.1), RDG is the reading value (that is, the displayed value), FS is the full-scale value, and the previous item in the brackets represents the A/D converter and functional converter (such as voltage divider, current divider, true effective value converter), the latter is the error due to digitization. In formula (2.2.2), n is the variation of the quantization error reflected in the last digit. If the error of n words is converted into a percentage of the full scale, it becomes formula (2.2.1). Formula (2.2.3) is special, some manufacturers use this expression, and one of the last two items represents the error introduced by other environments or functions.
Digital multimeters are far more accurate than analog analog multimeters. Taking the accuracy index of the basic range for measuring DC voltage as an example, the 3 and a half digits can reach ± 0.5%, and the 4 and a half digits can reach 0.03%. For example: OI857 and OI859CF multimeters. The accuracy of the multimeter is a very important indicator, which reflects the quality and technological capability of the multimeter.
