Next generation SoC for ultrasonic water meter lowers the total costs significantly
Leading manufacturers of water and heat meters worldwide are already using the acam messelectronic system-on-chip (SoC) TDC-GP22 in their ultrasonic water and heat meters. The advantages of the acam TDC measurement technology are high precision measurement and very low power consumption. Acam evaluates the successor GP30-beta in thorough tests which delivered impressive results. The first preliminary test kits will be available for developers in the first quarter of 2014. Customer samples are planned for the 4th quarter of 2014.
Measurement tasks are completely separated from device management and its external communications
The GP30 is a complex front-end solution integrating digital signal processing (32-bit µP) and providing a legal-for-trade output signal over a UART, Pulse or SPI interface. The connected standard MCU can focus on the device management and the operation of external interfaces such as radio communication. The measurement task is completely independent from the device management. The GP30 provides temperature sensor connectivity and processing functionality for heat meters like the GP22. In addition to that the GP30 offers now a 4- wire connection for temperature sensors in its final version.
The overall power consumption of the water or heat meter system has been substantially lowered compared to the GP22. This is a vital factor for water meters because their sampling rate is higher. The front end part consumes as only one third of the power required by the GP22 . Therefore a highly optimized 32-bit µP (77µA/MHz) has been integrated to enable the operation of water or heat meter with an ultra-low current consumption.
Power optimization through intelligent firmware code
Ultrasonic water meters for flow metering operate typically with a sampling rate of 8 Hz. With this sampling rate a GP30 runs including all calculations and mathematical corrections with approximately as little as 7µA. That way the GP30 consumes only about 2µA for the operation of permanent operations as 1.8V LDO and its 32 kHz oscillator. Further 5 µA to measure the flow and process the acquired flow data. The 32-Bit µP consumes only about 2.2 µA, resulting in nearly 0.3 µA per measurement per second. This value is not achievable by a standalone low-power standard MCU. The final chip will provide further power optimizations and further improvements through intelligent firmware.
The target for the long battery life for the complete device is:
2/3 AA battery size: Two calibration periods + reserve (15 years)
AA battery size: > 20 years
Assuming a current consumption of 4µA as of todays´ standard MCU, those values have been reached already.
Additional electronics in water meters lowers the total costs of a meter
Mechanical water meters are still the most commonly type of meters used today. Electronics still play no major role here but this will change in the next years gradually and consistently.
The production costs of mechanical water meter without electronics will not be lower than those of ultrasonic water meters but the total costs over the entire life span are significantly higher. For a full picture also the advantages of “smart metering” have to be taken into account and have to be added.
There are three main reasons for the total costs:
- Aging: mechanical counters wear out over time and the measurement becomes less accurate. Mechanical meters measure too little when they are operated for a long time. In a typical consumption period this adds up to $30-$55 of not billed consumption per calibration period.
- Two calibration periods: due to the much lower wear in ultrasonic measuring, these meters can be used over two calibration periods instead of using only one calibration period. This saves a complete meter including all installation services. It is a significant advantage for the global water utility providers.
- Better leak detection: a mechanical counter with its moving parts has a higher start-up flow, which also increases with age. Ultrasound offers a long-term stable solution to measure flows even less than 1 l/h nowadays. This is a great advantage and makes it possible to detect a leak like for example a dripping tap.
Conclusion: Ultrasonic water meters are superior to mechanical meters regarding the total costs over the entire operating time. Even purely mechanical meters without electronics are more expensive in this regard. The pure productions costs of Electronically readable mechanical meters (hybrid meters) are in general already higher than ultrasonic meters. At the same time ultrasonic water meters provide a higher measuring quality and increased long term stability. We are at the beginning of a process of changing at least 2/3 of all water meters worldwide to ultrasonic solutions. The technology is available already. In the heat meters these changes have already taken place during the last 5 years. The reasons to do so were similar but with regards to water meters the benefits are even greater to opt for a change.
ams Sensors Germany GmbH
acam messelectronic GmbH, located in Stutensee near Karlsruhe, Germany, is an owner-operated company specializing in solutions and concepts for highly precise measurement technology. The 25 person team of Presidents Augustin Braun and Andreas Larsch uses standardized CMOS technologies to implement customer requests in application-specific ICs all the way up to system-on-chips (SoC), significantly more simplified and with fewer risks than comparable suppliers. acam messelectronic GmbH was founded in 1996 and in 2013 achieved a sales volume of 7.2 million EUROs. acam's PICOTURN rpm measurement system is used in almost all current car makes of VW, BMW, Audi, Daimler, GM and Ford. Other customers include NASA, whose Lunar Reconnaissance Orbiter (LRO) acam helped equip, as well as ESA, which implemented the docking mechanism of the ATV (Automatic Transport Vehicle) for the ISS with the help of acam messelectronic GmbH.