Calibration of a multimeter device
Basic principle: When the detected potential forms a closed loop with a known potential of equal magnitude and opposite direction, no current flows in the circuit due to potential balance. At this time, the potential to be measured can be known based on the known potential.
practice:
1. When the standard current flows through a precision resistor box, you can get many corresponding accurate voltage values on the precision resistor box.
2. Connect a precision resistor and a potentiometer for current adjustment in series to the circuit formed by the resistance box and the power supply. Precision resistor→resistance box→potentiometer→power supply→return to the precision resistor.
3. Now measure the potential on the precision resistor without affecting the current. The method is to add the standard potential to the top (your 200mv), adjust the potentiometer (the voltage drop on the precision resistor will change accordingly), until no current is generated in the first loop composed of the standard battery and the precision resistor (use the tester current meter), at this time the potential (voltage drop) on the precision resistor is equal to the standard potential, so the standard current value is obtained. Assuming that your precision resistor is 2 ohms, the standard current drawn is 100 milliamps.
At this time, if your standard resistor box is 1 ohm, then the voltage drop across the resistor box is 1X100=100 millivolts. Similarly, if the resistor box is 100 ohms, the voltage drop is 10 volts. You can now know the voltage drop across the resistor box directly from its reading.
How to calibrate a multimeter
4. One end of the multimeter to be calibrated is connected to the end of the resistance box and the potentiometer, and the other end is connected to the other end of the resistance box connected to the precision resistor through the same galvanometer. Multimeter → resistance box → galvanometer → return to the multimeter to form the third loop.
Pay attention to adjusting the potentiometer at any time to let the galvanometer point to zero. At this time, the standard current will not change because your multimeter is connected to the measurement circuit, so the measured value is accurate. (If the potentiometer is not adjusted, shunting will occur as soon as the multimeter is connected, the standard current will change, and the measured value will be inaccurate)
