Piezoelectric measuring technology benefits

Piezoelectric sensors have many benefits and are among the key technologies that determine business success for industrial manufacturers.


Figure 1: The piezoelectric effect can be put into good use with a quartz crystal. When subject to a mechanical load, it generates a charge signal that is directly proportional to the acting force. Among advantages of piezoelectric quartz technology incluMeasurement technology based on the piezoelectric principle delivers a remarkable increase in process reliability within a company's production chain, coupled with a sustained improvement in productivity—opening up the way to zero defect production in joining, assembly, and testing.

The piezoelectric effect

Piezoelectric measurement technology optimizes and controls production processes by measuring force, pressure, acceleration, and torque. When a mechanical load is applied to the quartz crystal used in the sensor technology, the crystal generates a charge signal that is directly proportional to the force acting on it. What is the benefit? Due to the high rigidity of the crystal, the measuring deflection is low-usually within the range of a few micrometers. When the tested processes are fast and dynamic, the high natural frequency of the quartz proves to be an advantage. Various piezoelectric effects are differentiated according to the position of the polar crystal axes in relation to the acting force:

Shear effect: Similarly to the longitudinal effect, the piezoelectric sensitivity involved in the shear effect is independent of the size and shape of the piezoelectric element. Shear-sensitive piezoelectric elements are used for sensors that measure shear forces, torque and strain, and also for accelerometers. They are suitable for use in sensors that behave excellently even in case of temperature changes.

Figure 2: Depending on the installation conditions, various sensors are available to provide optimal production monitoring: 1. Direct measurement (the entire process force passes through the sensor); 2. Indirect measurement (a small part of the force passCharge amplifiers convert the charge produced by a piezoelectric sensor into a proportional voltage. The amplifier acts as an integrator, constantly compensating the electrical charge produced by the sensor on the range capacitor, in proportion to the acting amplifier.

Quartz sensors allow both direct and indirect force measurements. For direct measurements, the sensor is positioned fully in the force flux, and it measures the entire force. This approach yields high measurement accuracy that is virtually independent of the force application point. If the sensor cannot be positioned directly in the force flux, it will only measure part of the force; the remainder passes through the structure in which it is mounted. (This is known as the force shunt.) With indirect force measurement, strain sensors are used to measure the process force indirectly via the structural strain. Quartz sensors are exceptionally stable, rugged, and compact. These attributes account for their widespread use in research and development as well as production and industrial testing technology. 

Benefits of piezo sensors

Measurements with piezoelectric quartz force sensors deliver benefits for dynamic and quasi-static measurements. For example, a dynamic force measurement is required for aging and load investigations for automotive components. The quartz force sensors consist of active sensor elements that generate a linear charge signal at the output, proportional to the acting force. This means that they can be used for multiple measuring ranges, because the force is measured directly via the sensor elements rather than indirectly through the deformation of a structure. This feature explains why these measuring elements can measure across several decades, with no need to exchange them when measuring different forces.

Figure 3: Kistler's maXYmos XY monitors can monitor and evaluate the quality of a product or manufacturing step on the basis of a profile. With the help of evaluation objects, the user adapts the curve evaluation to the specific monitoring task. Image cou

Another benefit piezoelectric sensors have for overload protection is that piezoelectric quartz force sensors react to load, not strain. This means that virtually no displacement occurs during the measurement. The pressure resistance of most sensors is 3.0 x 108 Pa, so massive overloading is possible without the risk of pressure-induced destruction. Even if the sensor is overloaded beyond its permitted measuring range, no damage will occur, and there will be no zero point offsets, fatigue, or linearity changes.

Piezoelectric sensors also offer added value in terms of stable sensitivity. Quartz force sensors feature a solid-state design, and quartz does not exhibit any signs of aging. Quartz elements are not displaced under load, so sensitivity changes are unlikely-eliminating the need for frequent calibrations. These advantages save time and money.

Dimensions are often a critical factor in the choice of a force sensor. In this regard, piezoelectric quartz force sensors have the advantage. They require minimal space, so the mass load they add in dynamic investigations is negligible.

Figure 4: Small force sensors are compact and save space–integration into the machine design is optimized. Image courtesy: Kistler Group

Other advantages of piezoelectric quartz technology include high output voltages (5 or 10 V with an output that generates an electrical output proportional to applied acceleration) and wide temperature ranges (-73 to 204 C/-99 to 399 F), as well as low acquisition and lifecycle costs. For certain applications, quartz force sensors offer a variety of technical benefits with the advantage of major cost reductions. 

Figure 5: With a narrow diameter of 8 mm, this measuring pin improves the design of Kistler strain sensors. Image courtesy: Kistler GroupQuality assurance

So the data captured by highly sensitive piezoelectric sensors can be used, it is visualized, evaluated, and documented in suitable monitoring systems. Systems of this sort have to be integrated into production so the quality of the manufactured products can be verified and/or assessed. Especially if many individual components are assembled to form one product, each component must already be tested by the suppliers. This is the only way to guarantee the quality of the end product. In assembly technology, for example, monitoring systems can reliably track the production process. The result: production can be optimized toward the goal of zero-defect production, and at the same time, cost efficiency is maximized.

Stefan Schäfer is the product manager in the production monitoring business field at KistlerInstrumente AG in Winterthur (Switzerland). Edited by Emily Guenther, associate content manager, Control Engineering, CFE Media, eguenther@cfemedia.com.

Key Concepts

  • The benefits of piezoelectric sensors
  • How piezoelectric technology optimizes and increases process reliability
  • Piezoelectric quartz technology's cost savings for industrial manufacturers. 

Consider this

What kind of monitoring systems are necessary to extract the data from piezoelectric sensors?

ONLINE extra

The piezoelectric effect was discovered by Pierre and Jacques Curie in 1880. In 1950, Walter P. Kistler patented the charge amplifier for piezoelectric signals, paving the way for the exploitation of an effect that had been known for decades.


No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
Additive manufacturing benefits; HMI and sensor tips; System integrator advice; Innovations from the industry
Robotic safety, collaboration, standards; DCS migration tips; IT/OT convergence; 2017 Control Engineering Salary and Career Survey
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me