Smart Flow Meter Solutions for Gas, Water and Heat Utility Meters

Infrastructure life-time Extension

In order to optimize service frequency, battery life times in this type of application need to last 10-15 years. TI's MSP430 Ultra Low Power MCU's fit seamlessly into this thought process by combining high-performance with low power.

Gas Meter – Power

As part of maximizing battery life, the correct selection of an ultra-low quiescent current power management device is a key to optimizing the low power of the MSP430. While running the MCU directly from the battery may work (within the specified MCU operating range) and seem to save the cost of power management components, the lack of voltage regulation means much higher MCU stand-by power consumption and lower battery life. This can lead to higher maintenance costs that will far offset any cost savings observed by eliminating the regulator. Regulating the MCU and peripheral communication ICs at the lowest possible voltage will optimize power savings and lengthen battery life.

Depending on the type of battery used and the operating mode (full load) duty cycle of the gas meter, there are multiple choices in power management solutions. For simple, low duty cycle (long stand-by) applications, using batteries with a fairly flat discharge curve (such as primary cell Li-SOCl2) the use of ultra-low Iq LDOs can provide long battery life at very low cost. For higher operating duty cycle applications, the use of a low Iq DCDC regulator with power savings mode (for light loads) provides higher efficiency with a modest increase in cost.

For applications using batteries with a linear discharge curve, such as multi-cell alkaline or NiXX, the use of a low-Iq buck/boost converter will maximize battery life by providing regulation down to discharge voltages as low as 1.8-volts. For use of single-cell or small coin cell batteries, where the battery voltage can be less than the regulated voltage, the use of low-Iq boost converters can provide regulation with input voltages as low as 0.7-volts.

Although full operation of the MCU and peripheral communication ICs can be optimized at one voltage, in stand-by mode, these devices can operate at much lower voltages (simply maintaining RTC and memory). The use of DCDC converters and LDOs with dynamic voltage scaling (usually implemented with a V-Select logic pin) can further increase battery life.

Analog Sensing

The mechanical forces in gas meters can be measured/detected by various types of sensors. Because voltages are very low, precise low-noise amplifiers (for flow and temperature), and instrumentation amps (for pressure) such as the OPA2209 and INA10x, respectively, are needed at the front end. Usually the voltage is digitized with precision ADCs such as the ADS125x.

The ADS125x are precision, wide dynamic range, delta-sigma, Analog-to-Digital (A/D) converters with 18 to 24-bit resolution operating from a single +5V supply and guarantee no missing codes. They are ideal for high-resolution measurement applications like cardiac diagnostics, smart transmitters, industrial process control, weigh scales.

By supporting such features, TI enables you to prepare accurate bills, perform regular balances and reconciliation, and provide real-time usage information for optimal energy savings for gas meters and several other smart grid gas meter  solutions. 

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