Ultrasonic water meters are some of the most in-demand meters on the market, and for good reason: they’re highly accurate, low-maintenance, and easy to install. But how do they measure water flow without any moving parts?
ULTRASONIC: A STATIC WATER METER TECHNOLOGY
Ultrasonic water meters are a type of static, or solid-state, water meters (other types of solid-state meters include electromagnetic field meters or “mag meters”). In other words, they have no moving parts, much like a modern computer hard drive. Unlike mechanical water meters, they require a power source and what they measure is the velocity of the water, from which they calculate the flow rate.
The benefits of solid-state meters are numerous.
No moving parts means no clogs – and that means lower maintenance!
Solid-state meters have greater accuracy over time, as moving parts inevitably degrade over their many years in service.
In the case of ultrasonic metering, the technology can be scaled in size, making it possible to have one family of meters for almost every application.
Solid-state meters are lighter than their mechanical equivalents, making them easier to transport and install.
Because the measuring chamber is open, water flowing through a solid-state meter loses less pressure than when flowing through a mechanical meter – in other words, a more efficient water system.
The downsides to solid-state meters are relatively few.
This meter type requires power, meaning either electric current or a battery. Either method introduces a possible failure point (a loss of power or a dying battery).
Some solid-state meters are susceptible to “noise” (stray currents or signals from other components), which if not accounted for can cause an inaccurate reading.
Because solid-state meters measure the velocity of the water as opposed to the volume, the measuring chamber must remain at “full pipe” for accurate measurement. In other words, air trapped in the meter can create inaccuracy.
Ultrasonic meters aren’t the only type of solid-state meters, but they have key advantages. For one, ultrasonic meters are excellent at making extremely low-flow measurements. This has a two-part benefit: it increases the revenue of water utilities by measuring every drop, and it can detect leaks that cost customers money – or even threaten to damage their home or business if left unchecked!
Additionally, ultrasonic technology is very energy-efficient, meaning that the meter’s batteries can have a very long life. This makes it possible to have a high sampling rate, which again leads to a very high accuracy for the entire life of the meter. State-of-the-art ultrasonic water meters can sample as often as four times a second – in contrast, some electromagnetic water meters are limited to sampling as infrequently as once every thirty seconds.
Products and reference designs of Ultrasonic Heat Meter
DC/DC power supply
Heat meters have digital, analog, and RF blocks with individual DC power requirements. Depending power levels TI has DC/DC converters, LDOs and power management ICs (PMIC) that can help to reduce power dissipation and size in the solution. DC/DC power supply includes Linear & low-dropout (LDO) regulators、Boost converters (integrated switch)、Buck converters (integrated switch)、Supervisor & reset ICs、Load switches、Battery fuel gauges、Comparators、General-purpose op amps、Precision ADCs, the corresponding products are TLV703、TPS61046、TPS62840、TPS3839、TPS22860、BQ35100、TLV9030、LM358B、ADS124S06
Metrology
The metrology subsystem of a heat meter measures the volumetric flow of water through the pipe plus precisely measures the temperature differential between water inflow and outflow. Ultrasonic measurement eliminates all mechanical components and can provide greater accuracy and reliability throughout the product lifetime. Metrology includes MSP430 microcontrollers、Precision ADCs、Linear & low-dropout (LDO) regulators、Supervisor & reset ICs、Shunt voltage references、General-purpose op amps、ESD protection diodes、Analog temperature sensors、Digital temperature sensors, the corresponding products are MSP430FR6007、ADS122U04、TPS7A02、TPS3839、LM4040、TLV9001、TPD6E004、LMT70A、TMP116
Application processor
Heat meters require a host MCU to calculate the flow rate, to control the segment display, and to execute all required communications stacks. Low power consumption is a critical concern in this battery powered application. Application processor includes MSP430 microcontrollers、Battery fuel gauges、Supervisor & reset ICs、Real-time clocks (RTCs) & timers、Comparators、General-purpose op amps, the corresponding products are MSP430F67791A、BQ35100、TPS3839、TPL5010、TLV9030、LM358B
Wireless communication
Heat meters use wireless communication to automatically report consumption data to the service operator. Low power consumption and RF sensitivity are important considerations. Wireless communication includes Low-power 2.4-GHz products、Sub-1 GHz transceivers、Other wireless products、Wi-Fi products、Sub-1 GHz wireless MCUs、MSP430 microcontrollers、General-purpose op amps、ESD protection diodes, the corresponding products are CC2674R10、CC1200、RF430CL330H、CC3200、CC1312R、MSP430FR6007、TLV9001、TPD6E004
Wired communication
Heat meters use wired communication to automatically report consumption data to the service operator. MBUS is the most common wired communications standard in this industry. Wired communication includes RS-485 & RS-422 transceivers、ESD protection diodes、Linear & low-dropout (LDO) regulators, the corresponding products are SN65HVD3082E、ESD351、TLV703
Anti-tamper
Heat meters monitor for potential tampering for safety purposes and to assure accurate billing. Many different types of sensors can be used to detect tampering. Anti-tamper includes Inductive sensor AFEs、D-type flip-flops、AND gates, the corresponding products are LDC0851、SN74LVC1G79、SN74LVC1G08
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