Basic error issues of multimeters-calculation method of multimeter errors

Basic error issues of multimeters_calculation method of multimeter errors

Basic error of multimeter

There are two ways to express the basic error of a multimeter.

For DC and AC voltage blocks and current blocks, it is expressed as a percentage of the upper limit of the working part of the scale. The scales of these blocks are linear or close to linear; for electric blocks, because the scale is nonlinear, the total arc of the scale is used instead. The long percentage represents the basic error.

The basic error value of electrical resistance indicated on the multimeter manual or on the dial is only applicable to the center position of the ohm scale (i.e., the ohm center). The basic errors at other scales are greater than this value.

The basic error range of the multimeter is shown in Table 1. The specific value can be found on the dial of the multimeter.

The accuracy of a multimeter refers to the measurement range (200mv/2v/20v/200v/1000v) and error range (+-(0.5%+3)) of the meter.

For example:
If the fixed value is 110V DC, it must be set to 200V DC. Its measurement error range is 110v+(+-(0.5%+3))v

If the fixed value is 220V AC, it must be set to the AC 750V range. Its measurement error range is 220v+(+-(0.8%+5))v

If the value is incorrect, check whether the battery is out of power.

Take the DC voltage 2V point as an example:

The basic accuracy is: ±(0.5%+3), if your multimeter's 2V range resolution is 0.001V;

Then the upper limit of error=2*(1+0.5%)+0.001*3=2.013V

Lower limit of error=2*(1-0.5%)-0.001*3=1.987V

So the error of 2V is ±0.013V

Calculation method of multimeter error

question:
A 50 yuan low-end digital multimeter is often used to measure battery voltage at 20V. I once measured an accurate voltage of 1.4V, and this meter showed 1.39, with an error of 0.01. When measuring multiple fully charged lithium batteries, they were all 4.17V. This charger has an 1879 chip and should be fully charged at an accurate 4.20. The seller of the charger explained: 1.4*3=4.2, 0.01*3=0.03, 4.20-0.03=4.17. Excuse me, if the multimeter has an error, in the case I gave an example, should 4.2V be displayed as 4.19 or 4.17?

answer:

Error: %＝0.01/1.4×100≈0.71%(0.0071)

When the error is 0.71%:

4.2×0.0071≈0.03(V)

4.2-0.03＝4.17(V)