Resistance measurement with a multimeter - tips and tricks
Multimeter resistance measurement of the three major steps
1, the multimeter we use, whether in measuring voltage or current, resistance, is a common one. When we need to measure resistance, we first need to adjust to the ohm gear. Generally there are: × 1, × 10, × 100, × 1000 several stops.
2, before the measurement if the pointer of the table or (digital multimeter two arm short circuit when the reading is not zero), it will make the reading has zero error. If we find before the test, not zero, we must first adjust it to zero position, the method is as follows:
3, select the multiplier
The use of multimeter resistance meter resistance meter resistance meter resistance meter resistance meter resistance, in order to facilitate accurate readings, as far as possible to make the needle pointing to the middle part of the dial, so you need to properly select the multiplier block. If the multimeter does not × 10k multiplier block, you can choose the closest block.
Principle of resistance measurement by multimeter
The principle of measuring resistance with a multimeter is actually based on Ohm's law. The voltage of the multimeter is the voltage of the battery, and it has several resistance values, including the resistance we want to test, its adjustable resistance (the different gears of the multimeter, its internal resistance is different), and its fixed resistance. And the current is calculated when our test resistance is equal to zero. This gives us the formula: I = U/(Rg + R fixed + R adjusted + R measured) U is the voltage of its internal battery, Rg is the resistance of the meter head, R fixed, a constant resistance in series with the meter head, R adjusted, a variable resistance for zeroing, and R measured, the resistance to be measured. When the measured resistance Rx = 0, the current in the circuit is maximum, adjust R so that the deflection angle of the pointer of the measuring mechanism for the full scale value, at this time the value of the current in the circuit I0 = E / R. When the measured resistance Rx increases, the current I = E / (R + Rx) gradually decreases, and the deflection angle of the pointer is also reduced. Therefore, the resistance scale on the dial of the multi-meter is reversed and unevenly graduated. If the measured resistance Rx = R, then the current I = I0/2 and the angle of deflection of the pointer is half the full angle of deflection. Therefore, the resistance value marked at the midpoint of the scale (known as the median resistance) that is, the range of the internal resistance value of the multi-meter. Usually the effective reading range of the resistance value scale is 0.1 to 10 times the value of the median resistance.
