How do you calculate the accuracy (or uncertainty) of a digital multimeter?
The accuracy of the multimeter, also known as uncertainty by some manufacturers, is generally written as "within one year after leaving the factory, measured at an operating temperature of 18°C ~ 28°C (64°F ~ 82°F) and relative humidity of less than 80%, ± (0.8% of the reading + 2 words)." Many buyers, or users, are not very clear about this and often ask. I assume here, there is a meter, in a certain range, for example, is DC 200V gear, is written in this way, the measured value, in the meter shows 100.0, then this time its correct value, should be how much. I think for the general user, can completely ignore the accuracy of the calculation, directly that is DC 100V can be. According to the manufacturer's accuracy calculations, in measuring 100V (display 100.0), the error is ± (0.8% * 1000 + 2) = ± 10, that is, the error of 1.0V, everyone in the substitution of readings, do not take into account the decimal point to display the value of the substitution of the calculation of the calculated value, plus a decimal point and then the original readings to go to the freight rate, such as this case, then the correct value of 100.0 ± 1.0, should be DC 100.0 ± 1.0, the correct value. 1.0, should be between 99.0~101.0V DC.
What is the difference between three-and-a-half digits and four-and-a-half digits of a digital multimeter?
Three and a half digits are also called 3 1/2 digits (read as three and a half digits) and four and a half digits are also called 4 1/2 (read as four and a half digits). We know that an analogue quantity, after quantization, converted to digital, the precision of its representation is related to the number of bits, the more bits, the closer to the original value, the more accurate (this is in general, without regard to other circumstances, if the quantized value of 1.00000V, then, with a one-bit representation and N-bit representation is the same (:). So in general, the more bits, the more accurate, that is, four and a half bits is more accurate than three and a half bits.
