Use Case: Tamper Detection

The device SAM L22 is targeted for segment LCD and/or battery powered applications such as: Among the above, energy meter is the typical application using this feature. Hence, the end user application regarding energy meter is discussed.

An energy meter is a device that measures the amount of electrical energy supplied to a residential or commercial building. The most common unit of measurement made by a meter is the kilowatt hour, which is equal to the amount of energy used by a load of one kilowatt in one hour.

A typical energy meter also requires a Real Time Clock (RTC) for tariff information. The RTC required for a metering application must be very accurate (< 5ppm) for Time of Day (TOD), which involves dividing the day, month, and year into tariff slots. Higher rates are applied at peak load periods and lower tariff rates at off-peak load periods. In addition to the tariff information the RTC in SAM L22 is also capable of detecting the tamper. SAM L22 has the tamper detection as an additional feature of RTC.

Meter tampering is an illegal method employed by consumers to gain entry, break into meter to deplete key functionalities, with the goal of reducing or completely eliminating the cost of energy usage. Traditional electricity meters have no ability to detect or deal with tampering because they only measure energy based on the voltage and current flowing between the inlet and outlet terminals. In such meters, tampering has become very easy and detection is harder.

All electronic meters have a microcontroller/microprocessor/ mixed-signal IC that performs energy measurement. These devices are very powerful and will directly contribute to the robustness of any meter. Energy is the instantaneous product of AC voltage and AC current averaged over time. Separate sensors for voltage and current will convert AC-mains voltage and current to a reduced and acceptable input for analog-to-digital converters (ADCs) (called as analog frontend) processing in the digital domain.

There are various tampering methods, which accumulates under following four categories:

  1. 1.Physical tampering.
  2. 2.Magnetic interference.
  3. 3.Removing wires.
  4. 4.Phase neutral Interchange.