TDC-GP30 Ultrasonic Flow Converter

March 28th, 2018

The TDC-GP30 is the next generation of ultrasonic flow converters. Besides an improved analog time-of-flight front end, it also includes a 32-bit CPU and memory for on-chip data post-processing and the complete flow calculation. This highly sophisticated circuit has been designed for use as a stand-alone component single-chip replacement for mechanical flow meters - using a pulse output, and as a two-chip solution (GP30 + external microcontroller) for applications requiring other interfaces – such as wireless flowmeters, LCD based meters, or similar. With the powerful built-in CPU and specialized ROM-based firmware, the GP30 can be used for many types of ultrasonic heat and water meters. It includes all flow and temperature measurement calculations internally, plus allows for highly customized configurations using customer-defined firmware routines and the internal CPU.

Because of the high-resolution of the internal time-to-digital converter and front-end ability to measure signal amplitudes, the GP30 can detect very low flows - aka leaks - down to 0.5 liter/hour or better in quiet systems, and detect anomalies in the flow, such as air bubbles, empty spool pieces, or aging of the spool piece. These are unique qualities of the GP30 not found in other solutions.

The GP30 is designed for driving external ultrasonic transducers and can be configured for extremely low power, making battery operated flow meters a reality, for example, 6 μA at 8 Hz, including flow and temperature calculations.

Key features are shown in the block diagram below also include:

  • High performance + ultra-low power Harvard architecture 32-bit CPU with
    • 128 * 32-bit NVRAM (non-volatile RAM) for user firmware parameter & data
    • 4k * 8-bit NVRAM (non-volatile RAM) for user firmware program code
    • 4k * 8-bit ROM for system task code and special flow library code
  • Capable of MID-compliant flow & temperature calculation, GP30-supported
  • Flexible interfaces, SPI, UART, pulse (flow only)
  • Amplitude measurements of the received signal for a secure bubble, aging, and empty spool piece detection

The GP30 SOC is available as QFN32 or QFN40 package, with the QFN40 package able to manage an external circuit for gas meters or larger diameter pipes needing boosted signal levels.

The GP30 is designed for autonomous operation. In self -controlled flow meter mode it triggers all measurements and does data processing to deliver flow information, independent of external control. It can also be configured to wake up an external microcontroller for communication of results. Operation in this mode utilizes the internal 32-bit CPU and embedded firmware. The firmware code memory and the firmware data memory are zero static power NVRAMs. Since they don’t draw current when not in use, they are not switched down and remain permanently usable.

Innovative companies are using the GP30 to further the development of smart systems that can very accurately measure the amount of water delivered to specific zones, measure the viscosity of fluids, measure gas flow, and other unique applications where ultrasonic techniques can be leveraged to replace older mechanical mechanisms. As more IoT applications become not only technically feasible but also financially and environmentally necessary, the GP30 will be able to lead the way to cost-effective battery-operated solutions.