Active resistance is size, the return conductivity. For measurement of this parameter ohmmeters of various designs, measuring bridges and other devices are used.
Instruction
1. To measure the active resistance of a component by an analog ohmmeter, switch it to the mode with the minimum sensitivity, close probes among themselves then the regulator set an arrow precisely to zero. Then open probes and connect them to a component. If the arrow does not deviate (or will almost not deviate), switch an ohmmeter to more sensitive limit, again calibrate as it is stated above then connect to a component. Without forgetting to carry out calibration after each switching of limits, repeat operation until the arrow does not deviate approximately on a half of a scale. Read resistance on the scale corresponding to the chosen limit.
2. If measurement is carried out by means of the digital device having function of an ohmmeter, carry out measurement also, with only that difference that zeroing is not required to be made - it is carried out automatically, and the corresponding regulator on the device is absent.
3. To measure component resistance by means of the bridge device, connect it to entrance terminals, choose the least sensitive limit then slow rotation of the handle from the beginning of a scale by its end or on the contrary achieve zero indications of the indicator or loss of a sound in dynamics (depending on a structure of the bridge). If it does not work well, switch the bridge to other limit. Repeat operation until it turns out to balance the bridge. Then read indications on the scale corresponding to the chosen limit.
4. Resistance of some loadings changes when passing on them rated current. Such is, for example, glow lamp: if to measure its resistance by an ohmmeter in the switched-off state, it will be very small, and during the work it considerably increases. To learn what it becomes, turn on consistently with a lamp the ampermeter, and parallel to it - the voltmeter. Include food, then substitute indications of devices in a formula: R=U/I where R is resistance, Ohm, U is tension, In, I - current, And. Before dismantling of a chain surely cut off power it.