Technical Dictionary Measurement of voltage, current and resistance If you want to check the serviceability of various electrical systems of your car, not necessarily immediately contact an electrician. On sale there are many different devices, from which you'll be able to check the status of the electrical system. The probe with lamp (with contact-needle). Use it to check the presence of voltage in an electrical circuit. The brighter the lamp is lit, the higher the voltage. The needle pierced the wire insulation under test. The other terminal device on the wire is connected to "weight" (the car body).
A WARNING The probe with an incandescent lamp consumes a lot of power, so it can not be used for the inspection of electronic devices (eg controller). This requires a voltage tester with LED. |
Probe with LED. Depending on the performance of this device detects the presence of DC and AC voltage in the range 6-700 V. visually the presence of voltage is determined by the ignition of the LED. Simple devices of this type are inexpensive. Universal tester (multimeter). This instrument can measure voltage, current (DC and AC) and resistance. You can use inexpensive device with a digital display. Power of the device is usually carried out by an autonomous battery. Measurement of voltage. In order to measure, for example, the battery voltage at idle, lead to the negative terminal of the device, connect to the negative terminal of the battery or attach to the "masses." Connect the positive terminal to the positive terminal of the battery or check the wire. If the instrument shows only 10.4 V, this indicates circuit in one cell of the battery. Also check the battery voltage at the starter, the resulting value of less than 8 indicates that the battery is not all right. Current measurement. To do this, you must break the chain and connect the device between contacts. When measuring is enough to disconnect the connector and connect a wire between two of its terminals.
A WARNING Always remember thresholds that can measure your tester. On contact these consumers as a starter, proceed very high currents which may damage the instrument during measurement. |
Resistance measurement. In this case, the tester is checked whether the current passes through the wire or a switch. If current flows smoothly, the resistance value will be zero. If in any place there is open, the resistance value will tend to infinity. Furthermore, it is possible to find out what is the internal resistance of a particular device. When measuring the resistance of the wire it is necessary to expose the ends and attach each to different terminals of the device (Fig. 9.7). When installing the measurement values should always start with the maximum value. | 
