The Method of Reducing Errors in Measuring Resistance with Pointer Multimeter
To achieve accurate measurement of resistance with a pointer multimeter, the following points should be noted:
1. Detection resistance file accuracy
Before testing the resistance, you should first make a basic assessment of the accuracy of the resistance file of the pointer meter you use.
First use a flat screwdriver to calibrate the mechanical zero position, then switch to the resistance gear to short-circuit the test leads, and adjust the Ω knob to align the pointer to the zero Ω position of the full scale. In the next step, you can use a standard resistance or a resistance box to perform a test, so that you can know the accuracy of the instrument. If you don't have these conditions, you can also find another pointer multimeter and use its DC voltage file as a resistance box. The resistance value of each file =Ω/Ⅴxfull-scale voltage value. for example:
MF47's 2.5v internal resistance = 20Kⅹ2.5ⅴ = 50KΩ. Other stalls can be deduced by analogy.
2. The instrument should be placed flat
The balance of the pointer must be adjusted before leaving the factory to ensure that the meter can be used normally in any posture. However, the error is different when the multimeter is in different postures, and the error is the smallest when it is placed flat. So for maximum accuracy, the meter must lie flat.
3. Try to eliminate the contact resistance of the knob
Due to the different working principles, the current flowing through the function switch of the pointer meter is larger than that of the digital meter. Therefore, the same contact resistance is negligible for digital watches, but it may have adverse effects on pointer watches, especially the Rx1 file. Therefore, it is best to rotate the function knob repeatedly for 1 to 2 turns before measurement to eliminate contact resistance and ensure measurement accuracy.
4. The battery should be fully charged
The Ω gear of the pointer meter has a full-scale zero-adjustment knob, and its function is to make the meter work normally when the battery power is in different conditions. Sometimes, although the old battery can still achieve full-scale zero adjustment, the different power and internal resistance of the new and old batteries still have an impact on the accuracy of the Ω range. Some multimeters are so small that they can be ignored, while others are more obvious. For example, MF10 will have some influence, while MF47 will be negligible.
5. Reduce parallax
When buying a pointer watch, it is best to choose a dial with a reflector, which can minimize parallax by overlapping with the pointer in the mirror. Or choose one with a smaller gap between the pointer and the dial, which is also beneficial to reduce parallax.
In addition, there are some other things to pay attention to: do not measure resistance with electricity or online; do not touch the measured resistance with both hands at the same time; do not place the meter in a strong magnetic field; when selecting gears, try to make the measured resistance value in the center of the dial.
