The higher the resistance setting of the multimeter, the greater the output voltage?
The output voltage of the resistance range of the pointer multimeter is basically equal to the voltage of the battery in the meter. For example, Rx1~RX1K of MF47 type are 1.5V, and Rx10K is 9V. MF10 type R x1 ~ R x10K is 1.5V, R x 100K 15V.
However, these gears with the same output voltage have different external current output capabilities due to different circuit designs and different internal resistances. The higher the gear, the smaller the current. For example, a small tungsten filament light bulb will emit light when measured at Rx1 level, but will not emit light when measured at Rx1K or above. But for LED lamp beads, since the conduction voltage is above 1.8ⅴ, even though the Rⅹ1 gear can output a large current, it still cannot be lit. On the contrary, if you use the Rx10K or 100K gear of the 9v or 15v battery, even if the current is very small, the LED lamp beads can be turned on and emit very weak light.
The digital multimeter is different. Because there is an amplifier in the meter and to reduce the power consumption of the meter, the output voltage of the resistance range is very low. Taking the 9205 meter as an example, the output voltage of 200Ω to 20MΩ is only a few tenths of a volt, and only the diode and 200M voltages are slightly higher.
The diode level is the cut-off area that breaks through the PN junction. The output no-load voltage is generally above 2.5V, and the current exceeds 1mA when the test leads are short-circuited. In the 200MΩ range, because the current through the resistor being measured is too small, in order to obtain sufficient sampling voltage drop, the output voltage is around 1.5v, but the current when the test leads are short-circuited is less than 5μA.
Therefore, the output voltage of the resistance range of the multimeter does not gradually increase with the change of the range, but is arranged to meet the normal operation of the multimeter.
There is a 1.5V battery and a 9V battery inside the analog multimeter. The function of these two batteries is to supply power to the resistance gear. That is to say, even if you remove these two batteries, the analog multimeter will have a DC voltage gear and an AC voltage gear. All DC current levels can be measured, because these three levels absorb signals from the external circuit under test, and after passing through the internal voltage divider resistor, shunt resistor, voltage divider/shunt/rectifier, the meter head is unified. To measure, only the resistance range uses the internal battery as a power source. The resistance range of the pointer multimeter is designed using the principle of voltammetry to measure resistance. That is to say, the resistance is measured based on the current flowing through the resistance being measured. We know the resistance It has the function of blocking current. According to this principle, the resistance is measured. That is to say, if the resistance of the resistance being measured is larger, the current flowing through the resistance being measured is smaller. At this time, the angle of deflection of the pointer is also smaller, indicating the resistance being measured. The resistance value is very large. On the contrary, if the resistance value of the resistor being measured is smaller, the current flowing through the resistor being measured is larger. At this time, the angle of deflection of the pointer is also larger, indicating that the resistance value of the resistor being measured is very small. It is designed based on this principle. Resistance gear.
The R×10K range of the analog multimeter is powered by an internal 9V battery. R×1K R×100 R×10 R×1 are all powered by internal 1.5V.
In the digital multimeter, the open circuit voltage of the diode gear is, that is, the voltage between the VΩ hole and the COM hole is about 2.5V-2.8V, while the open circuit voltage of the resistance gear is about 0.3V-0.6V in all ranges, and the current of each gear is exactly are different, you need to measure this yourself
