Calculating the accuracy of a digital multimeter
The accuracy of the multimeter, also known as uncertainty by some manufacturers, is generally written as "within one year from the factory, operating temperature 18 ° C ~ 28 ° C (64 ° F ~ 82 ° F), relative humidity less than 80 [%] conditions measured, ± (0.8 [%] 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 the case, then the correct value for 100.0 ± 1.0, should be between 99.0~101.0V DC.
Digital multimeter three-and-a-half and four-and-a-half difference
Three and a half is also called 31/2 bits (read as three and a half bits), four and a half is also called 41/2 (read as four and a half bits). We know that an analogue quantity, after quantization, converted to digital, the accuracy 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 representation of the same as the representation of the N-bit (:). 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.
