Here we go over how to properly install and mount Piezoelectric force transducers, what a Piezoelectric transducer and much more.

1. Phone Number: 1-800-550-0280
Contact Email: contact@tacunasystems.com
Website: https://tacunasystems.com/
Installing And Mounting Piezoelec-
tric Force Transducers
Introduction
The application requirements determine the category of piezoelectric trans-
ducer that is chosen; therefore, a selection of the transducer type has to
ensure the various characteristics – sensitivity, geometry, rated capacity,
excitation voltage, loading conditions, creep, frequency, linearity, etc. – are
optimal enough to ensure that the system of application operates efficiently
within certain error limits and tolerances.
The next step after transducer type selection is the installation and mount-
ing process. These processes are very delicate – owing to the operating
principle of the piezoelectric sensor – and involves other sub-processes.
This article discusses the various concepts and process that relates to the
installation and mounting of piezoelectric force transducers.
What Is A Piezoelectric Transducer?
First, it is important to understand that a piezoelectric force transducer is
simply a sensor that detects the applied force, deforms under this stressing
force, and then generate an electrical signal at its output terminals. This
electrical output signal is in the form of electric charges; hence the pro-
duced charges are proportionally indicative of the applied force.

2. Piezoelectric transducers operate based on the piezoelectric effect: piezoe-
lectricity is produced when a polarized crystalline material is stressed or de-
formed; the stress causes a shift in the orientation of the internal dipoles of
the material. It is almost similar to di-electricity, which is charge production
the shift of electrons in an insulator.
This transducer is modeled electrically as a charge source in series with a
capacitance that has an internal resistance and inductance. Figure 1 and 2
below depicts the piezoelectric effect and an electrical model.
Figure 1. The Piezoelectric Effect

3. Figure 2. An electrical model of a piezoelectric sensor
Furthermore, the mathematical formula that shows the relationship be-
tween the charge produced, the applied force, compliance, and the material
constant is expressed below. The compliance of the material is the inverse
of Young’s modulus.
The piezoelectric material in the transducer is attached to the body of the
transducer such that it lies along the loading axis, that is, the direction of
application of the dynamic force to be measured.

4. Installation Requirements
As it is widely the practice, the installation of this transducer has to be car-
ried out by a well-trained personnel who understands the various standard
safety requirements and guidelines.
In an industrial setting, the personnel should follow the installation design
details that contains information about the location of installation for the
transducer, the sealing of the transducer’s housing unit, the wiring dia-
grams, cable requirements, and grounding of the system. In addition, the
personnel should also be able to perform both the pre-installation testing
and loop testing – after the transducer has been installed in the system.
Read:
 Force and Weight Measurement Resources You Need to Learn
 Ways to Measure Forces in the Force Shunt
 Connecting a Force Sensor to a Data Acquisition Sensor
Mounting a Piezoelectric Force
Transducer
Mounting the device at the intended location requires considering some
factors which are stated as follows:
 Accessibility: the mounting position should be chosen such that the
device is easily accessible to the authorized personnel for repairs
and maintenance.
 The orientation of the piezoelectric material inside the sensor to
be installed
 The transducer’s Geometric shape: based on the shape, the trans-
ducer should be mounted such that the orientation of the underlying
piezoelectric material ensures that the direction of applied stress and
the position of the output electrodes – that detects the output electric
field – are perpendicular to each other.
 Resonant frequency: the natural frequency of the piezoelectric ma-
terials can be as high as 100,000Hz and they are not self-damping.
Therefore, if it is not needed to drive the transducer to this frequency
level, then appropriate mounting measures should be taken against
it.

5.  Damping: Damping is necessary if the material is to be operated
normally especially at its natural frequency. Therefore, mounting
could provide damping by using spring elements to pre-compress the
transducer for more support, better rigidity, and firmness under vibra-
tions of different amplitudes. Damping also greatly improves linearity.
 Cabling: the electrode cables of the transducer must be kept
properly insulated and short. The cable should not be cut short or ex-
tended without special knowledge on how to cater for the new capac-
itance created by the new cable length. Also, during installation, the
open area of the cable should not be touched; as a matter of fact, the
cable contact should be kept free of dirt. The recommended wire type
for installing piezoelectric transducers is the Coaxial cable.
 Housing unit: the packaging of the transducer could be made a vac-
uum, to ensure the absence of air loading and proper damping. The
unit must be properly sealed against dust and dirt particles.
 Signal conditioning peripherals: These devices should be placed
as close as possible to the transducer so as to reduce the distance of
charge and signal transmission; it will help reduce unnecessary noise
coupling and voltage drops.
 Grounding and shielding: This is a very important step during in-
stallation. The transducer should be properly grounded to protect the
device. It should be noted that the piezoelectric material within the
sensor can act as an actuator in a process called the reverse piezoe-
lectric effect: it means that if an electrical time-varying signal – e.g.
AC voltages – is applied to the piezoelectric material, it starts vibrat-
ing at a certain frequency. There is, therefore, a crucial need for
proper shielding against electromagnetic interference.
Installation Components
The important installation components are mainly the piezoelectric trans-
ducer itself, the connecting cables, and the charge amplifier. The earlier
sections have addressed the operating principles of the transducer and ca-
bling is discussed under the mounting section. Therefore, the only one left
untouched is the charge amplifier.
The charge amplifier is an electronic circuit that converts the charge output
from the piezoelectric sensor to a voltage output. It is designed from an op-
erational amplifier with a high input impedance – usually a MOSFET input
stage, a suitable frequency response, and a low output impedance. In the
amplifier design, a feedback technique is used so as to allow for gain ad-
justment and to also filter the signal.

6. Figure 3 below shows the schematic of the charge amplifier connected with
the modeled cable and sensor parameters.
Figure 3. A Piezoelectric sensor – Charge Amplifier Circuit Schematic
In the diagram Q is the charge source in parallel with the sensor capaci-
tance Cp, Cc is the cable capacitance which is also in parallel with the sen-
sor parameters, Cf and Rf are the feedback capacitance and resistance re-
spectively.
In figure 2, it is shown that there is a resistance in series with the parallel
capacitance Cp; it is this resistance that causes charge leakage.
This type of amplifier design – charge amplifier, ensures the following:
 The calibration factor is fixed by the value of the feedback capaci-
tance and resistance Cf and Rf.
 A dynamic frequency range, as the time constant ( Rf*Cf), can be ad-
justed; it can be made large or small for low and high-frequency oper-
ations respectively, but only for dynamic loading.

7.  The elimination of the effects of the stray capacitances of the con-
necting cables Cc and that of the sensor Cp.
The above-stated influences of the charge amplifiers, therefore, enable the
piezoelectric transducer to have a high stability, wide dynamic range, good
temperature stability, good linearity, and low hysteresis.
In conclusion, the output terminal of the charge amplifier can then be con-
nected to an analog-to-digital and signal processing component or a volt-
age meter.
Important Transducer Characteristics
The following are the characteristics to expect from the datasheet of a pie-
zoelectric transducer which provides more information for an installation
process. They include the following
 Relative Dielectric Constant: it indicates displacement under a unit
electric field and zero stress
 Electromechanical Coupling Factor: it indicates the efficiency of
the transducer, that is, the relationship between the supplied electri-
cal energy and the output mechanical energy of the material.
 The Piezoelectric Distortion Constant: the resulting distortion
when an electric field of uniform strength is applied under zero stress
 The Voltage Output Coefficient: the effective electric field strength
under uniform stress but zero electrical displacements.
 Resonant Frequency: the natural frequency of vibration of the mate-
rial
 The Mechanical Quality Factor: this indicates the steepness of the
response of the material to a mechanical vibration that is equal or
close to the resonant frequency.
 Poisson’s Ratio: this is the ratio of the traverse strain to the axial
strain when a constant stress is applied to the material.
 Curie Temperature: The temperature level at which the material
loses its polarization and piezoelectric properties. It causes the
aligned dipoles to become disoriented.
 The Compliance: It is also called the elasticity constant and it is the
inverse of the Young’s Modulus, hence the ratio of the Strain to the
Stress.
Conclusion

8. The calibration of the installed transducer is performed after appropriate
mounting is completed; calibration simply involves comparing the reading
of the piezoelectric transducer to that of a known standard. This will help to
check systematic errors and improve accuracy.
The piezoelectric force transducer is only suitable for dynamic measure-
ments, hence it is widely used for ultrasonic applications, shock measuring
sensors, airbags, acceleration measurements, etc.; its small and compact
size makes it possible for it to be embedded inside miniature systems.
Sources
 The Instrumentation Reference Book, Edited by Walt Boyes
 Jayant Sirohi, Inderjit Chopra , “Fundamental Understanding of Pie-
zoelectric Strain Sensors,” Journal of Intelligent Material Systems
and Structures.
 Instrumentation: Transducers and Interfacing by B.R Bannister and
and D.G. Whitehead
Phone Number: 1-800-550-0280
Contact Email: contact@tacunasystems.com
Website: https://tacunasystems.com/