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New SoC from acam significantly simplifies electronics for ultrasonic water meters

Highly accurate and extremely energy efficient, the TDC-GP30 from acam heralds a new era for a full static measurement method in ultrasonic flow measurement. The integrated 32-bit µP performs mathematically complex and computationally intensive flow calculations with all the necessary corrections in an extremely power-efficient manner, while the external mi-cro-processor is fully relieved of this task. acam enables cost-effective development, production and service concepts while doing so.

Stutensee, Germany (5 May, 2015) - acam-messelectronic GmbH, a member of the ams group and an international company specializing in semi-conductors that focuses on the sensor industry, introduces a new member to its UFC (Ultrasonic Flow Converter) family, with the TDC-GP30. The design of new ultrasonic flow meters can be greatly simplified and shortened by the TDC-GP30, allowing manufacturers to develop cheaper, more compact and energy-efficient ultrasonic meters. The TDC-GP30 is a System-on-Chip solution with extremely low power consumption, which undertakes all the measurement tasks up to the calibrated output value.

In the development of the TDC-GP30, acam has specifically sought to address customer needs. The main objectives of the TDC-GP30 development were:

  • A universal solution for ultrasonic heating and water meters that is easy to adapt.
  • A single-chip solution for different industrial applications and for pure flow and/or volume measurement.
  • All flow, volume and temperature calculations to be done directly by TDC-GP30.
  • An external μP to be used only for the interfaces to LCD, wireless and other standard applications and no longer a part of the electronics assembly required by the legal metrology.
  • An integrated Standard Pulse Interface that allows a one-to-one coupling in the electronic assembly of mechanical and hybrid measuring instruments. Pulses of mechanical measuring instruments can be generated equivalent to the TDC-GP30. Existing processor solutions for echanical meter types as well as their software remain mostly unaffected in the process, while changing a mechanical flow measurement (e.g. with a propeller) with an ultrasonic metering tube.

Complete separation of the digitization of flow and volume of device management and external communication

The TDC-GP30 functions as a complete front-end solution with integrated digital signal processing (32-Bit µP) up to the output signal that can be calibrated and displays a real Single-Chip-solution up to the digital volume output through UART, Pulse and SPI, so that the subsequent standard MCU can be used exclusively for the management of communication of the measurement device - e.g. for wireless. 

TDC-GP30 works with the time-of-flight measuring principle
The TDC-GP30 measures the water flow with the help of high-precision time differences of ultrasonic pulses in the direction of the flow as well as against the flow. When used in cold water meters, the measured transit times of the ultrasonic impulses are additionally used for the necessary measurement of the water temperature, and the temperature dependence of the ultrasonic run time is thus put to a beneficial use. 

A value not yet reached on a low-power standard MCU basis

At a measuring rate of 8 Hz, typical for ultrasonic water counters, the complete TDC-GP30 requires only about 8 µA, including all calculations and mathematical corrections of the flow. While doing so, approx. 2 µA are consumed on permanent features such as 1.8V LDO and 32 kHz oscillator, and 6 µA for the implementation of the flow measurement and the automatically initiated calculation of the flow. The 32-Bit µP requires approx. 3.6 µA (0.45 µA/Measurement) while doing so - a value hitherto unachievable on a low-power standard MCU basis. This shows the effectiveness of a customized computer architecture as well as the OP-code tailor-made for it. The entire firmware is developed and maintained in assembler to achieve the most compact code in combination with highest performance and absolutely minimum power consumption. The extremely low power consumption of the chip allows the use of low-cost standard 2/3 AA or AA lithium thionyl chloride batteries. At a measurement frequency of 6-8 Hz, an operating time of more than 20 years can therefore be reached for water meters.
Intelligent firmware brings the full potential of the chip to the customer.

With the TDC-GP30 acam also offers firmware as an option for the integrated processors, which includes all functions up to the calibrated output value. This firmware is optimally matched to the processor, can be parameterized by the customer to a high degree and is thus a tool that can be applied universally in order to be able to carry out quick and secure developments.  For cold water meters (up to 60 °C), the necessary temperature measurement is carried out via the ultrasonic run time in water, so that no additional temperature sensor is required.

For customers that wish to develop their own firmware or extend the solution offered by acam, a convenient assembler with graphical use interface is available, which is included by default in the development system.  

Support with development and production

acam strongly supports customers in the necessary characterization of a new meter/measuring tube in development. In the process, the customer accepts (as usual) the characteristic of a new measu-ring tube type via n-flows and m-temperatures, and enters them in the development system of the TDC-GP30. An integrated "calculation engine" calculates the corresponding coefficients of the correction algorithm of the acam firmware from these customer entries and provides them in a downloadable file. These coefficients are finally stored in the corresponding NVRAM (non-volatile RAM)  area of the TDC-GP30.

This basic parameter set will then be used for the production of a meter type, which is characterized and adapted according to each production measuring tube. Only a 2-point calibration (two known flows in case of a known temperature) is required for the parameter adjustment. This presumes an appropriate production stability of the mechanical system (of the measuring tube). The basic parameter set can be used unchanged, as long as the property (the character) of the measuring tube type is moved in sufficiently close tolerances.

The professional tooling of the TDC-GP30

acam has been working with ultrasonic flow measurement since the company was founded. Each new acam development is based on an intensive exchange with its customers and the taking into account of their wishes andrequirements. acam understands the production processes of its customers and designs its products accordingly. Measuring accurately is a discipline that acam has mastered, as is providing customers a clear competitive advantage with a forward-thinking design.

Model of the production-ready TDC-GP30 now delivered to the first customers.

Since the beginning of 2014, the TDC-GP30 has been available in its beta version and has since undergone rigorous testing, in which it has delivered impressive results. In the meantime, the TDC-GP30 has been developed into a production-ready product and is also
available in samples. The first customers have already been supplied. Interested customers can therefore get the finished chip with the necessary development and programming environment just in time for Sensor+Test 2015 in Nuremberg. This also supports the characterization and calibration functions.

Technical data of the TDC-GP30:

High performance + ultra-low-power 32-Bit CPU with

  • 128 * 32 bit NVRAM (non-volatile RAM) for user firmware parameters and 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
  • Flow, volume and temperature calculation (MID-compliant) by the TDC-GP30, which can be calibrated
  • Flexible interfaces: SPI, UART, pulse (flow only)
  • 8 μA at 8 Hz measuring rate including all necessary calculations of the integrated µP.
  • < 5µA operating current in the typical water meter application by adaptive process control in the firmware

Very low space and component requirements.

Please visit us at our booth # 226 / hall 12 at Sensor + Test, May 19 - 21 2015, in Nuremberg. For more information on the TDC-GP30 ultrasonic flow converter please go to our website at

About acam-messelectronic

acam-messelectronic GmbH is a member of the ams group specialising in manufacturing ICs for TDC based measurement and converter technology. One of acam’s main lines of business is manufacturing ICs for ultrasonic flow measurement technology. acam is the global market leader with an approximate market share of 35% in heat flow meters. The company has been developing TDC based ICs since its foundation and today these are used by the leading heat flow, gas flow and water meter manufacturers.

There are 4 additional product groups (TDC, Picostrain, PicoCap, PicoTurn) with each supplying their respective fields of application  with optimal solutions for precise, current-saving, effective measurement and data processing. Many acam products are system-on-chip solutions with user-programmable microprocessors and NVMs. More information about acam can be found at

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Technical Contact

Georg Jedelhauser
acam-messelectronik GmbH
Director Marketing
T  +49 (0)7244-74 19-0

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Ulrike Anderwald
ams AG
Marketing Communications

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