Does the output voltage of a multimeter increase as its resistance range increases?
For a pointer type multimeter, the output voltage of the resistance range is basically equal to the voltage of the battery inside the meter. For example, the Rx1-RX1K of the MF47 model is 1.5V, and the Rx10K is 9V. MF10 type R x1~R x10K is 1.5V, R x 100K is 15V.
But these gears with the same output voltage have different abilities to output current externally due to different circuit designs and internal resistances. The higher the gear, the lower the current. For example, using Rx1 to measure tungsten filament small bulbs will emit light, while using Rx1K or higher will not emit light. However, for LED beads, due to the conduction voltage being above 1.8 V, even though R X 1 can output a large current, it is still unable to light them up. On the contrary, using a Rx10K or 100K range of 9V or 15V batteries can make the current very small and also make the LED beads conduct and emit very weak light.
A digital multimeter is different, as it has an amplifier inside and also reduces the power consumption of the instrument. Therefore, the output voltage of the resistance range is very low. Taking the 9205 meter as an example, the output voltage between 200 Ω and 20M Ω is only a few tenths of a volt, with only slightly higher voltages in the diode and 200M ranges.
The diode level is used to break through the cut-off zone of the PN junction, and the output no-load voltage is generally above 2.5V. When the probe is short circuited, the current also exceeds 1mA. In the 200M Ω range, due to the small current passing through the measured resistor, in order to obtain sufficient sampling voltage drop, the output voltage is around 1.5v, but the current when the probe is short circuited is still less than 5 μ A.
So the output voltage of the multimeter's resistance range does not gradually increase with gear changes, but is arranged to meet the normal operation of the multimeter.
The pointer multimeter has a 1.5V battery and a 9V battery inside, which are specifically used to supply power to the resistance range. This means that even if you remove these two batteries, the pointer multimeter, DC voltage range, AC voltage range, and DC current range can be measured, because these three ranges are all obtained by extracting signals from the external circuit being tested and passing through internal voltage divider, shunt resistor, and voltage divider/shunt/rectifier, We use a unified meter head for measurement, and only the internal battery is used as the power supply for the resistance range. The resistance range of the pointer multimeter is designed using the principle of measuring resistance using the volt ampere method, which means measuring the size of the resistance based on the current flowing through the measured resistance. We know that resistance has the effect of obstructing current, and we measure the size of the resistance based on this principle, That is to say, if the resistance value of the measured resistance is larger, the current flowing through the measured resistance will be smaller. At this point, the angle of pointer deflection will also be smaller, indicating that the resistance value of the measured resistance is large. On the contrary, if the resistance value of the measured resistance is smaller, the current flowing through the measured resistance will be larger. At this point, the angle of pointer deflection will also be larger, indicating that the resistance value of the measured resistance is very small. The resistance range designed based on this principle.
R in the pointer multimeter × The 10K gear is powered by an internal 9V battery. R × 1K R × 100 R × 10 R × Both use internal 1.5V power supply.
In a digital multimeter, the open circuit voltage of the diode range is, that is, the voltage between the V Ω hole and the COM hole is around 2.5V-2.8V, while the open circuit voltage of all ranges of the resistance range is around 0.3V-0.6V, and the current of each range is different. You need to measure this yourself
