The process of verification of integrity of an electrical circuit is called pro-ringing. Carry out this operation with the help both specialized devices - ohmmeters, and the combined measuring instruments having among other and such function.
Instruction
1. Remember once and for all that pro-call, as well as in general measurement of resistance, unlike measurement of current and tension, is always carried out at powered off a chain. Even if tension operating in a chain is safe for the person, they can damage the device and if are safe and for it - to distort results of measurements.
2. Get acquainted with the device device, to a pro-call of chains in which you are going to carry out. Perhaps, in it there are condensers continuing to store a charge and after de-energization. The way of their safe discharge depends on the capacity and tension up to which they are charged during the work. Remember that even after the discharge is carried out, it is possible to concern device details after tension on condensers is checked by the voltmeter. Consider that in some devices the discharge of the condenser can lead, for example, to a stop of the built-in hours or deleting of the non-volatile RAM.
3. Learn to transfer correctly the measuring device to the mode of an ohmmeter and to expose a measurement limit. As to do it, it is told in the instruction to the device. If it digital, too big resistance is usually displayed by figure 1 in the senior category and blackout of other categories, or letters ""O.L. "" (overload). On the arrow device at too big resistance of the shooter just will not deviate. If the mode sound pro-calls is chosen, at chain resistance less than 50 Ohms (for the majority of devices) the signal sounds.
4. At the arrow device after each switching of limits expose zero ohmmeter. Close probes among themselves, then rotation of the regulator combine an arrow with the end of a scale (for an ohmmeter scale it will be the beginning).
5. Remember arrangement of positive and negative probes at the device in the ohmmeter mode. At digital devices it usually same, as well as in the mode of the voltmeter and ampermeter, and at arrow upon transition to the ohmmeter mode the probes change roles. To check whether so it for concrete model of the device, is possible by means of the diode having marking.
6. Surely learn from the instruction to the device to what nests it is necessary to connect probes after switching in the ohmmeter mode.
7. If parallel to the checked chain there are others, capable the conductivity to distort result, temporarily disconnect them before measurement. Then do not forget to connect them back.
8. If the chain has to change resistance at change of polarity, connect to it an ohmmeter serially in one polarity, in another. Make sure that the chain or its separate element, for example, the diode really has such property.