Wednesday, August 27, 2008

Magnetic Tampering

Magnetic tampering technique is done by bringing a high powered magnet in close proximity of the domestic electricity meter. When this is done, the disc stops rotating. The circuit for the magnetic tampering detection circuit is as shown above.

The vital component used in the occurrence of the magnetic tampering technique in the domestic electricity meter is the Reed switch. The reed switch contains two magnetizable and electrically conductive reeds which have end portions separated by a small gap when the switch is open. The reeds are hermetically sealed in opposite ends of a tubular glass envelope.

In the magnetic tampering technique, a high power magnet is brought in contact with the electricity meter. When this happens, the rotor disc is exposed to a high magnetic field. Then the resultant opposing magnetic field to the rotor is highly increased leading to slowing down of rotor or perfect stopping of the disc rotation. The electricity meter is thus manipulated and ultimately power is consumed without being paid for.

Now when a reed switch is placed on the electricity meter and is connected to the micro controller, the magnetic tampering can be effectively identified. When a high power magnet is bought in proximity of the electricity meter in the presence of the Reed switch two leads come in contact with each other and result in the closed circuit thereby helping in detection of the signal by the micro controller. Thus the tampering is detected and the micro controller receives the information, which it passes on to the LCD unit and the GSM modem.