Microchip Technology Inc

Serial EERAM in Metering

  • EERAM allows meters to write consumption data 1000x more frequently than EEPROMs
  • More accurate consumption data
  • Real Time Data Logging – Modern meters need data to be written as frequently as ~2 times per second.

Data Logging

Electricity Meters today comprise of two broad sub-systems – the metering system and the communication system. The primary function of the metering system is to accurately measure energy consumption data. A lot of newer smart meters need to record meter data at least a couple of times a second or more frequently.  Real-time data logging helps make smart meters more efficient especially for prepaid systems. In a prepaid system, the end customer is typically charged per time period of use and longer the interval between these charges the wider the fluctuation in power consumption – in an ideal world the metering manufacturer would like to ensure charges can be deducted more frequently to ensure:

  1. their customer is actually paying for the exact amount of electricity consumed;
  2. the fluctuations in the amount of power consumed per charge is reduced.

Such frequent data logging requires data memory which has to have the ability to: 

  1. Write to memory instantly
  2. Write to memory unlimitedly and
  3. Reliably store Information.

EERAM offers an easy, low power, low-cost solution that can achieve all of these tasks reliably using a simple I2C interface.  The unlimited write cycles on the EERAM allows the system to log information continuously. The EERAM also stores this information reliably upon power loss without loss of data.

The communication system of the meter is responsible for transmitting metered data to the data center. The data logging system using the memory can also be used to provide information to be transmitted.

Metering grids are also equipped with data logging systems downstream at the grid to record overall power consumption and any changes in the load in real-time. These systems often need to write to memory at a high speed and constantly. These systems are also responsible for monitoring the operations status of the grid to ensure optimum power distribution and delivery. The EERAM’s instantaneous write capability couple with its unlimited write cycles makes them ideal for data logging systems at the power grid.

Tamper Detection

The EERAM is also equipped with a hardware store pin that allows any external trigger to set the Hardware Store Event Flag (a non-volatile bit in the Status Register). The external trigger could be set to anyone trying to open or tamper with the meter. By monitoring the status of the Hardware Store Event flag, designers can enable a simple mechanism to prevent tampering of the meter. A hardware store operation also ensures the contents of the SRAM is stored in to the EEPROM, ensuring the last data before the Hardware Store was reliably stored. This event flag can be reset in the status register at any time.

Summary of EERAM Applications in Utility Metering

Feature Benefit
Fast data-writing speed Protects against data loss in the event of a power failure
Read/write Cycle Endurance Permits Data Collection at frequent intervals
Back-up via Capacitor Eliminates the need for a battery back-up to preserve data

Metering Video Channel