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10.5.1. Voltage measurement

1. If the last exercises of the rechargeable battery were done less than 6 h back, turn on passing beam on 30 with that peak value tension fell at charging.

Fig. 9.6. Voltage measurement of the rechargeable battery by means of a multimeter. At value of tension lower than 12,5 In the battery it is necessary to load

2. In 4–5 min. measure tension between battery plugs. A red wire with the plug of a tester (multimeter) attach to the positive plug of the battery, black — to negative (fig. 9.6). At measurement all consumers have to be switched off.

Fig. 9.7. The principle of connection of a multimeter at measurement of current, tension and resistance. Consumers are, for example, lamps, a starter or the radio tape recorder

Fig. 9.8. By means of a special tester it is possible to establish a condition of the battery by measurement of its capacity. Measurement should not continue more than 10 with as the battery at the same time experiences big strain

Voltage measurement, current and resistance
If you want to check serviceability of various electric systems of your car, it is optional to address the electrician at once. On sale there are many various devices by means of which you will be able independently to check a condition of system of electric equipment.
Sampler with a lamp (with contact needle).
With its help it is possible to check presence of tension in an electric chain. The more brightly the lamp burns, the tension is higher.
The needle pierces isolation of the checked wire. Other plug of the device on a wire joins "weight" (a car body).

The sampler with the glow lamp consumes the big power therefore it cannot be used for checks of electronic devices (for example, the controller). Tension sampler with a light-emitting diode is for this purpose necessary.

Sampler with a light-emitting diode. Depending on execution this device defines presence of constant and alternating voltage within 6–700 V. Vizualno presence of tension is determined by light-emitting diode ignition. Simple devices of this kind cost not much.
Universal tester (multimeter). It is possible to measure by this device tension, current (constant and variable) and resistance. It is possible to use inexpensive devices with the digital display. Power supply of such device is, as a rule, carried out from the independent battery.
Voltage measurement. To measure, for example, tension of the rechargeable battery idling, attach a device wire with negative contact to the negative plug of the rechargeable battery or fix on "weight". Attach the positive plug to the positive plug of the battery or the checked wire. If the device shows only 10,4 B, it demonstrates short circuit in one of battery cans. Check also tension of the rechargeable battery at inclusion of a starter, the received value less than 8 V demonstrates that with the battery not everything is all right.
Measurement of current. For this purpose it is necessary to break off a chain and to connect the device between the opened contacts. At measurement will be to disconnect the contact socket enough and to connect a wire between two of its contacts.

Always you remember threshold values which your tester can measure. On contacts of such consumers as a starter, very big currents which can damage the device at measurement proceed.

Measurement of resistance. In this case a tester check whether there passes current through this or that wire or the switch. If current passes freely, value of resistance will be zero. If in any place there is a break, value of resistance will be strives for infinity. Besides, it is possible to find out what internal resistance has this or that device.
At measurement of resistance of a wire its ends it is necessary to bare and attach everyone to different plugs of the device (fig. 9.7). At installation of values of measurement it is always necessary to begin with the maximum value.
Measure the capacity of the rechargeable battery (fig. 9.8).