First, set the voltmeter to the measurement range that corresponds to the expected value of the measured voltage. Voltages in a car, as a rule, do not exceed 14 volts. An exception is the ignition system, where the ignition voltage can reach 30,000 volts. Such voltage can only be measured using a special measuring device or an oscilloscope.
If when using measuring instruments specifically designed for control measurements on vehicles, it is enough to turn on, in this case, the voltmeter by pressing the button, then when using combined control and measuring instruments, you must first make a number of decisions. First, you need to select the DC voltage measurement mode (DCV), as opposed to the AC voltage measurement mode (ACV). Then the measurement range is selected. Since there is no voltage higher than 14 V in the car, except for the ignition system, you can choose an upper measurement limit that is only slightly higher than this value (approximately 15-20 volts). If it is known for sure that the voltage to be measured is significantly lower, for example, in the region of 2 volts, then the device can be switched to a lower range, which will allow for greater measurement accuracy. If the voltage to be measured is higher than the one for which the range is selected, then the measuring device may be damaged.
Connect the measuring device wires in parallel to the current consumer. In this case, the measuring device wire with red insulation is connected to the electric wire coming from the positive terminal of the battery, and the device wire with black insulation is connected to the "ground" wire (-), or to the car body, for example, to the cylinder block.
Example of verification
If the engine starts with deviations from the norm because the starter speed is too low, it is advisable to check the battery voltage with the starter running. To do this, connect the red wire of the voltmeter (+) to the positive pole of the battery, and the black one to the car body (-). Then ask an assistant to work the starter and read the voltmeter reading. If the voltmeter registers a voltage of at least 10 volts (at a battery temperature of +20°C), then you need to check the battery and, perhaps, charge it before making further attempts to start the engine.
Article republished from the website: PEUGEOTBOOK.ru