WHITEPAPER – ULTRASONIC SENSORS FOR ESTIMATING CONSUMPTION
Dipl.-Phys. Birgit Schulze

Ultrasonic Sensors for Estimating Consumption
in Building Services Engineering and Industry
Highly Integrated Piezo Ceramics

Physik Instrumente (PI ) GmbH & Co. KG_Auf der Roemerstraße 1_76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019 E-mail info@pi.ws, www.pi.ws

Page 1 of 4

WHITEPAPER – ULTRASONIC SENSORS FOR ESTIMATING CONSUMPTION
Dipl.-Phys. Birgit Schulze

So-called "static flow rate meters" with ultrasonic

In principle, even the amounts of gas can be measured

transducers are used, for example, in modern building

with ultrasonic methods, but this is technically even more

servicescomplex.

engineeringformeasuring

thewater

consumption (Fig. 1). But also gas consumption can berecorded in this way. Piezoelectric components in

Ultrasonic Flow Rate Measurement

various designs - as plates, discs, or rings - can be used

The propagation time measurement and the so-called

as ultrasonic transducers. There are two different

Doppler effect (measurement of phase difference) aremeasuringtheprinciples

forlevelmeasurement:

The

two

fundamentalmeasurement

processes

inmeasurement of the propagation time or the Doppler

ultrasonic flow rate measurement. The piezo transducers

effect.

used in each case generate ultrasonic waves which are
inserted into the liquid diagonally to the direction of flow.
The measurement of the propagation time, also called
the traveling principle, is based on the alternate
transmission and reception of ultrasonic pulses in andagainst the direction of flow. Here, two piezo transducers
operating as both transmitter and receiver are arrangeddiagonally to the direction of flow in an acoustic path(Fig. 2).

Fig. 1 A conventional vane flow meter for recording theamount of water consumed in a household – today, themeasurement of consumption and flow rate isincreasingly recorded by ultrasonic sensors
In many areas, measuring the flow rate is fundamental
for controlling processes. An example for this is modernbuilding services engineering, where the consumption ofFig. 2 Principle of propagation time measurement by
ultrasoundwater, warm water or heating energy, e.g. from long-The entrainment of the wave packet in the flowing

distance heating, needs to be recorded, so that, on themedium (liquid or gaseous) causes a superimposition of

one hand, the precisely consumed amount can be billed

sound propagation velocity and flow velocity. The flow

and, on the other hand, sufficient supply is ensured.

velocity is proportional to the reciprocal of the difference

But also the metering processes in industrial automationand especially in chemical industry are very complex.

in the propagation times in and against the direction offlow.

Here, ultrasonic sensors are used for volume flowThe Doppler effect is used to evaluate the phase andmeasurement. Instead of weighing substance quantities,

frequency shift of the ultrasonic waves which area continuous volume measurement for overall processscattered or reflected by particles of liquid (Fig. 3). The

control is effected. Not only the flow velocity, but also thefrequency shift between the reflected wavefront emitted

concentration of certain substances can be detected –and

this being very important for tracking chemical reactions.

proportional to the flow velocity.

receivedbyPhysik Instrumente (PI ) GmbH & Co. KG_Auf der Roemerstraße 1_76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019 E-mail info@pi.ws, www.pi.ws

thesamePage 2 of 4piezotransduceris

WHITEPAPER – ULTRASONIC SENSORS FOR ESTIMATING CONSUMPTION
Dipl.-Phys. Birgit Schulze

This is important, for example, when liquids flow at ahigh pressure, when they are aggressive or when special
hygienic restrictions have to be fulfilled. Furthermore,
there are no abrasive effects on the measuring
equipment. The installation of clamp-on sensors issimple, the process is not disturbed.
Subsequently installed sensors are the ideal choice formonitoring
Fig. 3 Doppler effect (measurement of phase difference)
It applies to both methods that the efficiency of themeasurement depends on the tube diameters and on
their sound transmission characteristics.

Subsequent Installation ofMeasurement Devices or
In-the-Flow-Measurement

existing

systems

orfor

effectingmeasurements limited in time, with low effort.
Alternatively,

ultrasonictransducers

canalsobeintegrated in the flow (Fig. 5). This is especially well
suited for measuring environments where the wallmaterial has a very low sound transmission. Themeasuring precision of in-the-flow measurement is far
above the precision of external flow measurement.

Clamp-on sensors can be applied subsequently andinterference-free to a an existing system. The sensor has
no influence on the mass flow and does not get into
contact with the flowing media, all existing tubes remain
intact.

Fig. 5 Measurement cell for flow rate measurement byultrasound (Image: Hydrometer GmbH)

Ultrasonic Sensors from PI Ceramic
PI CeramicGmbHhasestablisheditselfasamanufacturer of customized piezo ceramics for a longtime now. The involvement of the customer fromdevelopment to series production goes without saying
whereby a great variety of geometries is possible, suchas plates, discs, tubes, rings or any other arbitrary
design. In this context, both the piezo components canFig. 4 Different OEM piezo ultrasonic transducers (top);bottom: piezo ceramics integrated in the sensor andequipped with electrical contacts

be used both as sensors and as actuators. Also piezo
elements, manufactured in large quantity for producing
flow meters, are from PI Ceramic.

Physik Instrumente (PI ) GmbH & Co. KG_Auf der Roemerstraße 1_76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019 E-mail info@pi.ws, www.pi.ws

Page 3 of 4

WHITEPAPER – ULTRASONIC SENSORS FOR ESTIMATING CONSUMPTION
Dipl.-Phys. Birgit Schulze

toWith 700 highly qualified employees all over the world,

manufacturing the piezo ceramic component for thethe PI Group is in a position to fulfill almost any

ultrasonic transducer, PI Ceramic takes also care of its

requirement with regard to innovative precision motion

integration with the customer product. This includes bothtechnology. All key technologies are developed in-house.

the electrical contacting of the elements according toThis allows the company to control every step of thecustomer requirements and the mounting of components

process, from design right down to shipment: Precision

provided by the customer, as well as the gluing or

mechanics and electronics as well as position sensors.

Whatthepiezo

experts offer

isnot

limitedcasting of the piezo ceramics. Additionally, PI Ceramic
can also provide suitable electronics.

by the subsidiary PI Ceramic in Lederhose, Germany,

PI Ceramic is one of the world's leading companies in
the field of piezo ceramics. The PICMA

The required piezoceramic elements are manufactured®

multilayer

actuator technology, which received an award for its
reliability, is one of many innovations of PI Ceramic.
Since 1992, PI Ceramic has been developing andmanufacturing piezo ceramic materials and components
for standard and OEM solutions: Piezo components,
ultrasonic transducers, actuators, and system solutions.
PI Ceramic, a subsidiary of PI (Physik Instrumente), is
located in the city of Lederhose, Thuringia, Germany.

one of the global leaders for piezo actuator and sensor
products.
PI miCos GmbH in Eschbach near Freiburg, Germany, isa specialist for positioning systems for ultrahigh vacuum
applications as well as parallel-kinematic positioning
systems with six degrees of freedom and customized
designs.

Author

The PI Group in Brief
Over the past four decades, PI (Physik Instrumente) with
headquarters in Karlsruhe, Germany, has become theleading manufacturer of nanopositioning systems withaccuracies in the nanometer range. With four company
sites in Germany and ten sales and service offices
abroad, the privately managed company operates

Dipl.-Phys. Birgit Schulze, Product Manager at Physik

globally.

Instrumente (PI) GmbH & Co. KG

Physik Instrumente (PI ) GmbH & Co. KG_Auf der Roemerstraße 1_76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019 E-mail info@pi.ws, www.pi.ws

Page 4 of 4