The AFE converts sensor signal with precalculation or without ready for any microcontroller operations
For the recording of consumption data, a sensor is always required, and these sensors are almost always only analogue. Using an AFE (analogue front end) the circuits will first be referred for processing of the sensor signal and sometimes will even be transformed into a digital signal. The quality and performance of the AFE is at least as important for the accurate measurement of consumption values as would be a first-class sensor.
The microcontroller (MCU) evaluates the signals from the sensor that are delivered through the AFE, and then processes the data
The microcontroller also controls, however, the entire energy meter including communication with the outside world. Thus, the MCU acts as the ‘brains’ of the smart meter. Since diverse peripheral units can be found on the chips of microcontrollers, the microcontroller, in addition to its control tasks, can also cover each type of different functionality within input/output. To win tenders in England, as well as in Eastern Europe, an energy meter must be capable of being prepaid, whereby ‘prepaid’ can also mean that the energy supplier receives a referral and then using data communication, unlocks a certain energy quota for an individual meter. The microcontroller takes over this monitoring of prepaid energy quotas and the associated activation of the line.
Longevity of the electricity meter a matter of power supply
Every intelligent energy meter requires a power supply – ‘only’ if it is a battery. Americans like to abbreviate the English term power supply to PS. In addition to the pure performance components such as voltage regulators and other semiconductors, power supplies also require sequencing ICs and other semiconductors to carry out controls.
Memory has a special role to play in consumption measuring devices, because it is where the device stores the consumption data
To prevent tampering here, secure non-volatile memory is required. Depending on the design of the overall system or of the microcontroller, the MCU already contains enough RAM and ROM, so that external memory (DRAM, Flash memory) are not always required.
Security and Authentication
In order to ensure comprehensive security, appropriate data security and authentication measures are required
In consumption measuring devices, data security deserves special attention for two reasons: Firstly, it is related to billing data, which for the energy and water supplier is none other than revenue; on the other side, this is countered by financial obligations in the form of energy costs. In plain language: the meters almost have a virtual equivalent in the form of money. The second aspect of security relates to the privacy of the consumer, because after all, the individual consumption of each respective consumer means nothing to third parties. In order to ensure comprehensive security, appropriate data security and authentication measures are required. To ensure security when communicating this billing data, an RSA encryption with a key length of at least 1048 bits should be used, at least for electricity and gas meters in Germany. The devices must be certified in accordance with EAL 4+, which is almost the same standard as that for a bank card.