How Can I Determine Resistor Voltage?

Resistance is one of the basic electrical parameters. It is often measured under DC conditions and also under AC conditions. The resistance range commonly used in engineering is from the negative seventh power of 10 to the negative fifteenth power of ten. When developing materials, conducting basic research, or performing experiments under special circumstances, the range of measuring resistance is generally extended to the negative eighteenth power close to zero to ten.

In the case of DC, the resistance R is defined according to the volt-ampere characteristic, that is, R = U / I , where U is the voltage across the resistor and I is the current flowing through the resistor. In the case of AC, the resistance R is defined by the power P , that is, R = P / I ² .

When servicing electrical equipment in our daily work, we often measure the resistance of equipment, components, and wiring. We refer to the resistance below 1 as a small resistance, the resistance between 1 100 is called the median resistance, and the resistance above 100 is called the large resistance. Because the resistance of the measured resistance is different, there are different measurement methods. There are two methods of measuring resistance: direct measurement and indirect measurement. ^[1]

Direct measurement

This is a method of measuring resistance using a special measuring instrument. For example: using a multimeter ohm scale to measure the resistance, you can read the data directly. In order to improve the measurement accuracy, DC can also be used.

Methods for measuring resistance include: (1) voltmeter-ammeter method, (2) resonance method, (3) ohmmeter method, (4) DC bridge method, (5) digital ohmmeter method, and so on.

The voltmeter-ammeter method is a method of calculating the resistance by measuring the current and the terminal voltage flowing through the measured resistance using Ohm's law. Although this method is simple, it is not used much.

The ohmmeter method measures the resistance of the resistor. Although the accuracy is not high, it can meet the general use requirements. This method, because of its convenience, is the most commonly used method for measuring resistance. The accuracy of the ohmmeter depends on the accuracy of the ammeter and the stability of the power emf, so its accuracy is not high and the measurement error is large. For this reason, it is necessary to check the ohmmeter regularly. The commonly used inspection method is to measure the precision resistance (standard resistance) and make corrections after comparison.

In addition to the ohmmeter method, the common method for measuring the resistance of a resistor is the bridge method. The measurement accuracy of the bridge method is higher than that of the ohmmeter method. There are many types of bridges. The most commonly used bridges are the Wheatstone bridge and the Kelvin bridge.

With the development of integrated circuits and digital technology, a variety of new resistance measurement instruments have been made. Digital ohmmeters are used to convert resistance into voltage, then use an analog-to-digital conversion voltmeter to measure the voltage, and then determine the resistance R to be measured from the voltage.

The main test items of variable resistors and potentiometers are to determine the resistance and adjust whether there is noise when adjusting the center tap position. For the method of measuring resistance, commonly used noise detection methods include ohmmeter method and oscilloscope method. ^[2]