Designing gas and water meters with Atmel MCUs

Gas and water meters – deployed by utility companies to measure usage stats – are typically designed to display data on a small segment LCD screen. Unlike standard electricity meters, gas and water meters are usually battery-operated, so power efficiency is clearly a key requirement.

RF communication has also become a critical feature for gas and water meters due to the advent of AMI architecture – with the Smart Electricity Meter often acting as the gateway to a utility for meter reading. In addition, an increasing number of gas and water meters are tapping into home area networks, requiring optimized security to protect data communications between devices.

The microcontrollers used in gas and water meters are generally 8- or 16-bit MCUs with ultra-low power features, often with integrated LCD segment drive capability. As such, selecting Atmel’s extensive MCU portfolio to design water and gas meters offers engineers a number of advantages.

“These include potentially best-in-class embedded 12-bit ADC and analog comparators to provide analog peripheral support, 1 µA watchdog and brown-out (monitor), picoPower to extend battery life, an event system to facilitate measurement whilst CPU is in SLEEP modes, 1.6V operation and lowest power 32 kHz crystal oscillator (650nA RTC),” an Atmel engineering rep told Bits & Pieces.

“There is also an option for embedded display controller, with high EMC performance reducing the need for external protection. Meanwhile, ±1% internal oscillators enable communications to run from internal oscillator (RC), as hardware authentication products with ultra-low standby current coupled with onboard microcontroller encryption enhances security for networked applications. In terms of transceivers, Atmel RF Transceivers offers best-in-class power consumption, while our single-chip Atmel ATmega128RFA1 combines a microcontroller and RF transceiver for efficient BOM.”

gasmeterchart

Unlike electricity measurement (voltage/current), notes the engineering rep, gas and water meters utilize a variety of parameters and techniques for flow metering. Examples include turbine and pelton wheel, optical acoustic doppler, thermal mass, vortex, magnetic, ultrasonic and coriolis flow meters (see the metrology sensor, shown in the block diagram above).

Analog-to-Digital Converters (ADC) and Digital-to-Analog (DAC) can also be useful peripherals to embed in the microcontroller, as they help facilitate flow measurement. Remember, flow meters are battery-powered, requiring power-efficient solutions capable of supporting up to 20 years of operation.

“Of course, LCD support is an important requirement. This capability can be driven serially with chip on glass, but must often be integrated into the microcontroller. Essential peripherals include serial communications and, frequently, security through encryption,” the engineering rep added.

“Dual clock input for high accuracy main clock (often used for timings in metrology) and second clock input for 32KHz for RTC. For Smart Meter and Smart Grid implementations, RF is the communication medium of choice to connect to the HAN to support AMR.”

Interested in learning more about using Atmel MCUs to design gas and water meters? Be sure to check out our extensive portfolio of MCUs that can be used to power such designs.

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