Why is the reading on the dial of the pointer multimeter 0Ω?
The ohm range of a pointer multimeter has three key points: 0 Ω, ∞, and center value. Because the ohm range itself is equipped with a battery, when the short-circuit resistance of the probe is zero, the current passing through the meter head is at its maximum. At this time, use a zero potentiometer to adjust the pointer to the full value, and we artificially define this as the zero position.
After separating the pens, we look at the resistance ∞ between the two probes. At this point, there is no current passing through the meter head, so the pointer does not move. This position is marked as ∞.
The ohm range of a pointer multimeter also has an important scale, which is the center resistance value.
Its center value in the ohm range is 16.5. Multiplying the coefficients at different gears represents the resistance value at the center position, for example, Rx1 represents 16.5 Ω, R60 is 165 Ω, R600 is 1650 Ω, Rx1K is 16.5K Ω, and Rx10K is 165K Ω.
This central scale value is very important as it marks the applicable range for measuring resistance in this gear. For example, Rx1 is most suitable for measuring resistance from a few ohms to several hundred ohms centered at 16.5, while Rx1K is suitable for measuring resistance from several K to several hundred K ohms. When we measure a 100 Ω resistor, the Rx1 pointer only deviates by about 1/6, making it clearer to see. When measured in 10K gear, the pointer still basically points to the 0 Ω position. It is difficult to observe subtle changes in the pointer. It can be seen that when measuring the same resistance with the same value of 0 Ω, the deviation amplitude of the pointer at different gears is different.
At the same time, the center scale of the ohm range is also the internal resistance of the multimeter for this range. Interested friends can also measure it themselves. The specific measurement method is to remove the battery of the pointer multimeter, short-circuit the battery clip with a wire, and then find a digital multimeter to directly measure.
