Single-chip hardware-plus-software for ultrasonic water flow metering

December 03, 2015 // By Graham Prophet
ams' acam TDC-GP30-F01 includes processor to compute water flow, volume and temperature measurements, making metering system implementation simple; ultra-low power consumption allows for up to 20 years’ operation on a single AA battery

Mixed-signal semi and sensor maker ams has augmented its family of ultrasonic flow meter ICs with the TDC-GP30-F01, a complete hardware and firmware measurement solution for cold water meters. Drawing a continuous current of 8.5µA when capturing flow measurements at a rate of 8 Hz, the chip can operate for up to 20 years on the energy available from a single AA lithium battery.

The TDC-GP30-F01 includes an ultrasonic flow measurement front end, a low-power 32-bit processor and firmware for converting the sensor’s analogue outputs to measurements of cold water flow, volume and temperature. This means that designers of water meters can use the TDC-GP30-F01 to implement a complete new 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 full 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, the TDC-GP30-F01’s firmware may be extended easily 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 TDC-GP30-F01 can therefore be made more compact, with a lower component count than competing approaches that require a complex companion processor for elaborate calculations, and other external components.

The TDC-GP30-F01 allows designers to build systems which offer 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 extremely repeatable, temperature-stable and