You will need
- multimeter, battery, 3 volt, flat screwdriver, pozvonochnye wire.
To determine the polarity of the wires coming from the charger, turn on the multimeter mode to measure DC voltages up to 20 volts, the black wire (negative) connect to the COM terminal and the red (positive) to the VΩmA socket. Connect the probes to the terminals of the charger and turn it on. If the display of the multimeter there is a minus sign, then the polarity is opposite, that is, the red test lead connected to the negative terminal, black to the positive terminal of the charger. In the absence of a minus sign correspond to the terminals connected to the probes.
To check the polarity of the speakers briefly touch his conclusions wiremi from the batteries on 3 volts. When moving the speaker cone outward, the polarity of the speaker terminals match the polarity of the battery. When moving inward, the polarity of the speaker outputs are the opposite polarity of the battery.
The power wire to the branded radios are easy to distinguish by color, which always corresponds to its wire. Black color wiresto be connected to the common ground or "minus" of power supply red wire plus the power connected to the ignition switch, yellow wire also refers to "plus" power supply, only connected to the battery. In any case, the wire with the fuse is the "power plus" power supply.
When replacing a faulty switch is not always possible to disconnect the house or apartment. In this case, will help to determine the phase (threat) wire flat screwdriver. It will help in the case when at carrying out any repair work you came across an unknown wire.
For continuity of the cable with the same wires turn on the multimeter mode to measure small resistances. In the case of continuity of the signal wires as a common pozvonochnika wire you can use a metal screen of the cable. On one side of the cable, connect the studied wire to the screen, and on the other hand connect the black test lead to the braid and touching alternately the wires, locate the closed the wire screen.
Advice 2: How to determine the polarity of the battery
In the automobile sold of lead-acid batteries direct (they are all domestic cars) and reverse polarity (installed on some machines of foreign production). Before buying a battery, it is necessary to accurately determine its polarity.
You will need
The service life of any battery is limited and is usually not more than five years. After the allotted time, there comes a time replacement unit. And if owners of cars of a domestic production the problem is to select the appropriate battery capacity and give preference to a particular brand, then the owners of imported cars need to find out before purchasing the polarity of the battery.
To achieve this task, the battery is removed from the battery socket and is positioned in such a way that by visual inspection from above its terminals must be at the bottom. Please note that one of them is a little thinner than the other (it is negative).
If the negative terminal is located on the accumulator on the left (bottom), the battery reverse polarity.
In cases where a thinner terminal on the right battery polarity.
To finally verify the correctness of the polarity of the battery, reconnect the voltmeter. The red probe of the device removes the voltage from the large terminal and the black thin. The reading on the scale without the minus sign confirms the studied parameters of the battery.
Install the battery by improper polarity in the car face the fact that its terminals are not be able to attach the cables.