Proving the Business Case for the Internet of Things

Water meter IC can last 20 years on single AA battery

Steve Rogerson
December 15, 2015
An ultrasonic flow meter IC from Austria Microsystems (AMS) provides complete hardware and firmware measurement for cold water meters. The TDC-GP30-F01 draws a continuous current of 8.5µA when capturing flow measurements at a rate of 8Hz, meaning the chip can operate for up to 20 years on the energy available from a single AA lithium battery.
The device includes an ultrasonic flow measurement front end, a low-power 32bit processor and firmware for converting the sensor’s analogue outputs to measurements of cold-water flow, volume and temperature. This means designers of water meters can use it to implement a complete ultrasonic water meter without developing their own firmware.
The flexible device may be adapted to complement a range of typical spool piece designs. Users only need to characterise their spool pieces. AMS provides a suite of hardware and software tools for evaluating, developing and characterising designs using the device. It also offers firmware functions such as error handling and power-saving modes when the flow rate is zero.
Users also have the option to add their own firmware code. For example, its firmware may be extended to implement a heat meter application.
The chip provides a direct connection to ultrasonic transducers, and only requires the addition of a simple microcontroller to operate a water meter’s peripheral functions, such as a display and connectivity. Designs based on the IC can therefore be made more compact, with a lower component count than approaches that require a complex companion processor for elaborate calculations, and other external components.
Designers can use the device to build systems that provide very accurate measurements of water flow and volume, making it suitable for use in water metering applications that are regulated by law. The device measures the difference in the time it takes ultrasound waves to travel upstream and downstream, providing repeatable, temperature-stable and accurate timing measurements. The high precision and stability of its flow measurements mean it is able to detect water leakage rates as low as 0.5 litres per hour in a good DN20 meter, many times lower than the minimum water flow measured by today’s widely used mechanical water meters.
The device has an SPI, UART or interface to an external microcontroller, or a pulse interface to emulate a conventional mechanical water meter’s signals. Users can therefore replace their former mechanical flow measurement system with a modern non-invasive flow meter without the need to rewrite their application software.
“Using competing devices, the ultrasonic time difference measurement principle calls for a separate processor to convert time information into calibrated flow and volume measurements, and requires the OEM to implement its own complex measurement application software,” said Georg Jedelhauser, marketing director at AMS. “The TDC-GP30-F01 is the only ultrasonic flow meter IC to handle the computations internally, providing designers with a much easier implementation as well as a smaller bill-of-materials.”
Samples of the device including a demonstration kit are available now. Volume production can be ordered.
With headquarters in Austria, AMS employs more than 1800 people globally and serves more than 8000 customers worldwide.