Electrical resistance – the physical quantity which characterizes properties of the carrying-out material. Resistance is defined as tension relation on the ends of the conductor to force of the current proceeding on it.
It is required to you
- Ohmmeter (multimeter, tester)
Instruction
1. To measure resistance size, the ohmmeter will be required. Today the modern devices called testers or multimeters are most often put into practice. These universal devices are capable to measure not only tension, but also current, capacitive characteristics, resistance.
2. The tester is equipped with two conclusions (probes). For measurement of resistance it is necessary to attach the first probe to one conclusion of the checked product (conductor), and other probe – to the second conclusion.
3. At the time of measurement of resistance between probes there is a potential difference. On the probe of black color the negative potential, and on the red probe – positive is formed.
4. The usual tester contains a number of ranges of measurement of electrical resistance, also particular treatments for "pro-calls" of conductors and check of transistor transitions are possible. Existence of the different modes usually is defined by concrete model of the device.
5. Prozvonka is irreplaceable by search of short circuit. In the presence of short circuit the sound signal is given, but only when the measured resistance is less than some allowable limit.
6. At measurement of resistance it is necessary to observe precautionary measures. So, it is impossible to take measurements in the scheme which contains power supplies. It can lead to irreversible damage of the device on which measurement is taken.
7. Some elements of the scheme have resistance which can depend on size and the direction of current and also on tension attached to them. These are the so-called elements having nonlinear resistance. Resistance of elements also depends on temperature. Temperature increase can lead as to increase, and reduction of resistance. Concrete features depend on material of which the element is made.