16.1.1. Check of deenergized chains


Before work we calibrate an ohmmeter. On the chosen limit of measurements (for the majority of chains to 200 Ohms) we close tips of probes. On the analog device the regulator of the 0 installation we expose an arrow on zero division. In household digital appliances there is no such regulator. Therefore for measurement of small sizes (to 1–2 Ohms), having short-circuited probes, we determine the internal resistance of an ohmmeter and its wires making 0,03–0,06 Ohms. This size needs to be subtracted from the received value of resistance.
For check of a chain we disconnect at least one its end (otherwise current will go to a round, on other sites of the scheme, and indications will be incorrect). It is better to put on a clip like "crocodile" one of probes of the device and to connect it to "weight". When checking devices with unilateral conductivity (for example, the vypryamitelny block of the generator) consider polarity of the device.
For check of windings of a starter, the generator, high-voltage wires, etc. we switch the device to the lower limit of measurements. In practice of accuracy of usual autotesters is not enough for check of sites of a chain where even the slightest increase in resistance, for example, because of bad contact is inadmissible. Therefore we pay attention to insignificant deviations of an arrow from zero division, and after measurement we double-check calibration of devices.
And mezhvitkovy we check short circuits of a winding for "case" the megohm meter (range of "M"). Many testers (arrow) during the work in this range require an additional source of a direct current. At its absence, being careful, we check a chain the lamp fed by voltage of 220 V.