This document outlines the syllabus for a course on sensors for engineering applications. The course is divided into 4 units that cover: sensor fundamentals and applications; position, weight, and force sensors; sound, ultrasound, and infrasound sensors; and biosensors and chemical sensors. Key topics covered include sensor characteristics, selection criteria, acceleration sensors, strain gage sensors, transducer principles, and biosensor technologies. The syllabus lists two required textbooks and two references for the course.

1. Sensors for Engineering Applications
Course Code: 19EC001
Prepared by
Dr. Jami Venkata Suman
Department of ECE

2. Syllabus
Unit I
Sensor Fundamentals and applications
Sensor Characteristics, System Characteristics, Instrument Selection, Data
Acquisition and Readout, Installation, Acceleration, Shock and Vibration Sensors:
Technology Fundamentals, Selecting and Specifying Accelerometers, Applicable
Standards, Interfacing and Designs
Sensor limitations, measurement issues and criteria
Unit II
Position and weight sensors
Position, direction, distances measurement-large scale, distance travelled, and
rotation. Force, Load and Weight Sensors: Quartz Sensors-Charge Mode High-
Impedance Piezoelectric Force Sensor, Voltage Mode Low-Impedance
Piezoelectric Force Sensor, Piezoelectric Force Sensor Construction, types of
Strain Gage Sensors
Special applications of strain gage sensors, gravitational sensing

3. Unit III
Sound, Ultrasound and Infrasound sensors
Principles, Audio to electrical sensors and transducers: moving iron microphone,
moving coil microphone, capacitor microphones. Microphone problems, frequency
and wavelengths. Electrical to audio transducers: moving iron transducer, moving
coil transducer, Capacitor transducers. Ultrasonic transducers, Infrasound sensors.
Building acoustics, Microphone Standards
Unit IV
Biosensors and Chemical Sensors
Introduction to Biosensors, Applications of Biosensors, Origin of Biosensors,
Bioreceptor Molecules, Transduction Mechanisms in Biosensors, Application
Range of Biosensors, Technology Fundamentals of chemical sensors, chemical
sensing techniques and applications.
Evolution of Biosensors, smoke sensors

4. Text Books:
1. Jon Wilson, Sensor Technology Hand Book, Newnes, 2004.
2. Ian R.Sinclair, Sensors and Transducers, third edition,
Newnes publications
3. Patranabis D, Principles of Industrial Instrumentation, TMH,
2nd edition
References:
1. Patranabis D, Sensors and Transducers, 2nd Edition, PHI,
New Delhi, 2010
2. E. O. Doeblin, Measurement System: Applications and
Design, fourth edition, McGraw Hill Publications

5. What is a Sensor?
A sensor is a device that converts a physical phenomenon into
an electrical signal. As such, sensors represent part of the
interface between the physical world and the world of
electrical devices, such as computers.
The other part of this interface is represented by actuators,
which convert electrical signals into physical phenomena.

7. • The Sensors are devices that responds to a physical
stimulus heat, light, sound, pressure, magnetism, motion,
etc, and convert that into an electrical signal.
• They perform an input function
• The Devices which perform an output function are
generally called Actuators and are used to control. some
external device, for example movement.
• Both sensors and actuators are collectively known as
Transducers. Transducers are devices used to convert
energy of one kind into energy of another kind.

8. Sensor Data Sheets
The data sheet is primarily a marketing document. It is typically
designed to highlight the positive attributes of a particular
sensor and emphasize some of the potential uses of the sensor,
and might neglect to comment on some of the negative
characteristics of the sensor.
In many cases, the sensor has been designed to meet a
particular performance specification for a specific customer, and
the data sheet will concentrate on the performance parameters
of greatest interest to this customer.

9. The prospective user is generally forced to make a
selection based on the characteristics available on
the product data sheet. Many performance
characteristics are shown on a typical data sheet.
Many manufacturers feel that the data sheet should
provide as much information as possible.
Therefore the instrumentation engineer must
understand the pertinent characteristics and how
they will affect the measurement.

10. SENSOR CHARACTERISTICS
1. Transfer Function:
The transfer function shows the functional relationship
between physical input signal and electrical output
signal.

11. 2. Sensitivity
The sensitivity is defined in terms of the relationship between
input physical signal and output electrical signal.
It is generally the ratio between a small change in electrical
signal to a small change in physical signal. As such, it may be
expressed as the derivative of the transfer function with
respect to physical signal. Typical units are volts/kelvin,
millivolts/kilopascal, etc..
A thermometer would have “high sensitivity” if a small
temperature change resulted in a large voltage change.

12. 3. Span or Dynamic Range:
The range of input physical signals that may be
converted to electrical signals by the sensor is the
dynamic range or span. Signals outside of this range are
expected to cause unacceptably large inaccuracy.
This span or dynamic range is usually specified by the
sensor supplier as the range over which other
performance characteristics described in the data sheets
are expected to apply.
Typical units are kelvin, pascal, newtons, etc.

13. 4. Accuracy or Uncertainty:
Uncertainty is generally defined as the largest expected error
between actual and ideal output signals.
Sometimes this is quoted as a fraction of the full-scale output or a
fraction of the reading.
For example, a thermometer might be guaranteed accurate to
within 5% of FSO (Full Scale Output).
“Accuracy” is generally considered by metrologists to be a
qualitative term, while “uncertainty” is quantitative.
For example one sensor might have better accuracy than another if
its uncertainty is 1% compared to the other with an uncertainty of
3%.

14. 5. Hysteresis:
Some sensors do not return to the same output value when
the input stimulus is cycled up or down. The width of the
expected error in terms of the measured quantity is defined
as the hysteresis.

15. 6. Nonlinearity (often called Linearity):
The maximum deviation from a linear transfer function over the
specified dynamic range. There are several measures of this
error. The most common compares the actual transfer function
with the “best straight line,” which lies midway between the two
parallel lines that encompass the entire transfer function over
the specified dynamic range of the device.

16. 7. Noise:
All sensors produce some output noise in addition to the output
signal. In some cases, the noise of the sensor is less than the noise
of the next element in the electronics, or less than the fluctuations
in the physical signal, in which case it is not important.
Many other cases exist in which the noise of the sensor limits the
performance of the system based on the sensor. Noise is generally
distributed across the frequency spectrum.
Many common noise sources produce a white noise distribution,
which is to say that the spectral noise density is the same at all
frequencies.
Since there is an inverse relationship between the bandwidth and
measurement time, it can be said that the noise decreases with the
square root of the measurement time.

17. 8. Resolution:
The resolution of a sensor is defined as the minimum
detectable signal fluctuation. Since fluctuations are temporal
phenomena, there is some relationship between the timescale
for the fluctuation and the minimum detectable amplitude.
Many sensors are limited by noise with a white spectral
distribution. In these cases, the resolution may be specified in
units of physical signal/root (Hz).
Sensor data sheets generally quote resolution in units of
signal/root (Hz) or they give a minimum detectable signal for
a specific measurement.

18. 9. Band Width :
The bandwidth of a sensor is the frequency range between
these two frequencies.

19. TOP SMART SENSORS
• Temperature Sensors
• Proximity Sensor
• Pressure Sensor
• Gas & Smoke Sensor
• Accelerometer Sensors
• Level Sensors
• Image Sensors
• Motion Detection Sensors
• Optical Sensors
• Gyroscope Sensors

30. SYSTEM CHARACTERISTICS
• The sensor and signal conditioners must be selected to work
together as a system.
• Moreover, the system must be selected to perform well in the
intended applications.
• Overall system accuracy is usually affected most by sensor
characteristics such as environmental effects and dynamic
characteristics.
• Amplifier characteristics such as
nonlinearity,
harmonic distortion and
flatness of the frequency response curve
are usually negligible when compared to sensor errors.

31. Instrument Selection
1. Selecting a sensor/signal conditioner system for
highly accurate measurements requires very skillful
and careful measurement engineering.
2. All environmental, mechanical, and measurement
conditions must be considered.
3. Installation must be carefully planned and carried
out.
4. The following are the guidelines to select and install
measurement systems for the best possible accuracy.

32. 1. Sensor
The most important element in a measurement
system is the sensor. If the data is distorted or
corrupted by the sensor, there is often little that
can be done to correct it.

33. Check the following to operate the sensor satisfactorily in
the measurement environment.
1. Temperature Range
2. Maximum Shock and Vibration
3. Humidity
4. Pressure
5. Acoustic Level
6. Corrosive Gases
7. Magnetic and RF Fields
8. Nuclear Radiation
9. Salt Spray
10. Transient Temperatures
11. Strain in the Mounting Surface

34. Check sensor characteristics to provide the desired data
accuracy.
1. Sensitivity
2. Frequency Response
3. Resonance Frequency
4. Minor Resonances
5. Internal Capacitance
6. Transverse Sensitivity
7. Amplitude Linearity and Hysteresis
8. Temperature Deviation
9. Weight and size
10. Internal Resistance at Maximum Temperature
11. Calibration Accuracy
12. Strain Sensitivity
13. Damping at Temperature Extremes
14. Zero Measurand Output
15. Thermal Zero Shift
16. Thermal Transient Response

35. 2. Cable
Cables and connectors are usually the weakest link in the
measurement system chain.
Check cable to operate satisfactorily in the measurement
environment.
1. Temperature Range
2. Humidity Conditions
Check the cable characteristics to provide the desired data accuracy
1. Low Noise
2. Size and Weight
3. Flexibility
4. Is Sealed Connection Required?

36. 3. Power Supply
Check the power supply to operate satisfactorily in the
measurement environment.
1. Temperature Range
2. Maximum Shock and Vibration
3. Humidity
4. Pressure
5. Acoustic Level
6. Corrosive Gases
7. Magnetic and RF Fields
8. Nuclear Radiation
9. Salt Spray

37. Check that is this the proper power supply for the
application?
Check the following to confirm.
1. Voltage Regulation
2. Current Regulation
3. Compliance Voltage
4. Output Voltage Adjustable?
5. Output Current Adjustable?
6. Long Output Lines?
7. Need for External Sensing
8. Isolation
9. Mode Card, if Required

38. Check the power supply characteristics to
provide the desired data accuracy.
1. Load Regulation
2. Line Regulation
3. Temperature Stability
4. Time Stability
5. Ripple and Noise
6. Output Impedance
7. Line-Transient Response
8. Noise to Ground
9. DC Isolation

39. 4. Amplifier
The amplifier must provide gain, impedance matching, output drive current,
and other signal processing.
Check the amplifier to operate satisfactorily in the measurement
environment.
1. Temperature Range
2. Maximum Shock and Vibration
3. Humidity
4. Pressure
5. Acoustic Level
6. Corrosive Gases
7. Magnetic and RF Fields
8. Nuclear Radiation
9. Salt Spray

40. Is this the proper amplifier for the application?
Check the following
1. Long Input Lines?
2. Need for Charge Amplifier
3. Need for Remote Charge Amplifier
4. Long Output Lines
5. Need for Power Amplifier
6. Airborne
7. Size, Weight, Power Limitations

41. Check the following whether the amplifier characteristics provide
the desired data accuracy.
1. Gain and Gain Stability
2. Frequency Response
3. Linearity
4. Stability
5. Phase Shift
6. Output Current and Voltage
7. Residual Noise
8. Input Impedance
9. Transient Response
10. Overload Capability
11. Common Mode Rejection
12. Zero-Temperature Coefficient
13. Gain-Temperature Coefficient

42. Data Acquisition and Readout
ALL of previous check items, plus Adequate
Resolution

43. Installation
Even the most carefully and thoughtfully
selected and calibrated system can produce
bad data if carelessly or ignorantly installed.

44. Sensor
Is the unit in good condition and ready to use?
Check:
1. Up-to-Date Calibration
2. Physical Condition
3. Case
4. Mounting Surface
5. Connector
6. Mounting Hardware
7. Inspect for Clean Connector
8. Internal Resistance

45. Is the mounting hardware in good condition and ready to use?
Check:
1. Mounting Surface Condition
2. Thread Condition
3. Burred End Slots
4. Insulated Stud
5. Insulation Resistance
6. Stud Damage by Over Torquing
7. Mounting Surface Clean and Flat
8. Sensor Base Surface Clean and Flat
9. Hole Drilled and Tapped Deep Enough
10. Correct Tap Size
11. Hole Properly Aligned Perpendicular to Mounting Surface
12. Stud Threads Lubricated
13. Sensor Mounted with Recommended Torque

46. Cement Mounting
Check:
1. Mounting Surface Clean and Flat
2. Dental Cement for Uneven Surfaces
3. Cement Cured Properly
4. Sensor Mounted to Cementing Stud with
Recommended Torque

47. Cable
Is the cable in good condition and ready for use?
Check:
1. Physical Condition
2. Cable Kinked, Crushed
3. Connector Threads, Pins
4. Inspect for Clean Connectors
5. Continuity
6. Insulation Resistance
7. Capacitance
8. All Cable Connections Secure
9. Cable Properly restrained
10. Excess Cable Coiled and Tied Down
11. Drip Loop Provided
12. Connectors Sealed and Potted, if Required

48. Power Supply, Amplifier, and Readout
Are the units in good condition and ready to use?
Check:
1. Up-to-Date Calibration
2. Physical Condition
3. Connectors
4. Case
5. Output Cables
6. Inspect for Clean Connectors
7. Mounted Securely
8. All Cable Connections Secure
9. Gain Hole Cover Sealed, if Required
10. Recommended Grounding in Use
When the above questions have been answered to the user’s
satisfaction, the measurement system has a high probability of
providing accurate data.

49. Accelerometers are sensing transducers that provide
an output proportional to acceleration, vibration and
shock.
These sensors have found a wide variety of applications
in both research and development arenas along with
everyday use.
In addition to the very technical test and measurement
applications, such as modal analysis, NVH (noise
vibration and harshness) and package testing
Accelerometers are also used in everyday devices such
as airbag sensors and automotive security alarms.
Acceleration, Shock and Vibration Sensors

50. Whenever a structure moves, it experiences
acceleration. Measurement of this acceleration helps
us gain a better understanding of the dynamic
characteristics that govern the behavior of the
object.
Modeling the behavior of a structure provides a
valuable technical tool that can then be used to
modify response, to enhance ruggedness, improve
durability or reduce the associated noise and
vibration.
Acceleration, Shock and Vibration Sensors

51. The most popular class of accelerometers is the
piezoelectric accelerometer.
This type of sensor is capable of measuring a wide
range of dynamic events.
Many other classes of accelerometers exist that are
used to measure constant or very low frequency
acceleration such as automobile braking, elevator
ride quality and even the gravitational pull of the
earth.
Accelerometers rely on Piezoresistive, Capacitive and
Servo technologies.

52. Piezoelectric Accelerometer
• Piezoelectric Accelerometer works based on the
use of a piezoelectric material as the sensing
element for the sensor.
• Piezoelectric materials are characterized by their
ability to output a proportional electrical signal to
the stress applied to the material.

53. The basic construction of a piezoelectric
accelerometer is shown below

54. The active elements of the accelerometer are the piezoelectric
elements.
The elements act as a spring, which has a stiffness k, and
connect the base of the accelerometer to the seismic masses.
When an input is present at the base of the accelerometer, a
force (F) is created on piezoelectric material proportional to the
applied acceleration (a) and size of the seismic mass (m).

55. The sensor is governed by Newton’s law of motion
F = ma.
The force experienced by the piezoelectric crystal is
proportional to the seismic mass times the input
acceleration.
The more mass or acceleration, the higher the applied
force and the more electrical output from the crystal.

56. The frequency response of the sensor is
determined by the resonant frequency of the
sensor.
The resonant frequency (ω) of the sensor can be
estimated by:
𝜔 = 𝑘/𝑚

58. Piezoelectric accelerometers can be classified into two
main categories based on their mode of operation.
1. Internally amplified accelerometers or IEPE
(internal electronic piezoelectric)
Internally amplified accelerometers or IEPE (internal
electronic piezoelectric) contain built-in microelectronic signal
conditioning.
2. Charge mode accelerometers
Charge mode accelerometers contain only the self-generating
piezoelectric sensing element and have a high impedance
charge output signal.

59. IEPE sensors incorporate built-in, signal-conditioning
electronics that function to convert the high-impedance
charge signal generated by the piezoelectric sensing
element into a usable low-impedance voltage signal that
can be readily transmitted, over ordinary two-wire or
coaxial cables, to any voltage readout or recording
device.
1. Internally amplified accelerometers or IEPE
(internal electronic piezoelectric)

60. IEPE sensor circuitry can also include other signal
conditioning features, such as gain, filtering and self-test
features.
The simplicity of use, high accuracy, broad frequency range,
and low cost of IEPE accelerometer systems make them the
recommended type for use in most vibration or shock
applications.
Limitation in temperature range.
The routine upper temperature limit of IEPE accelerometers is
250°F (121°C); however, specialty units are available that
operate to 350°F (175°C).

61. The electronics within IEPE accelerometers require excitation power
from a constant current, DC voltage source. This power source is
sometimes built into vibration meters, FFT analyzers and vibration
data collectors. A separate signal conditioner is required when none
is built into the readout. In addition to providing the required
excitation, power supplies may also incorporate additional signal
conditioning, such as gain, filtering, buffering and overload
indication. The typical system set-ups for IEPE accelerometers are
shown in below figure.

62. 2. Charge Mode Accelerometers
Charge mode sensors output a high-impedance, electrical charge
signal that is generated directly by the piezoelectric sensing element.
This signal is sensitive to corruption from environmental influences
and cable-generated noise. Therefore it requires the use of a special
low noise cable. To conduct accurate measurements, it is necessary
to condition this signal to a low-impedance voltage before it can be
input to a readout or recording device. A charge amplifier or in-line
charge converter is generally used for this purpose.

63. These devices utilize high-input-impedance, low-output-
impedance charge amplifiers with capacitive feedback. Adjusting
the value of the feedback capacitor alters the transfer function or
gain of the charge amplifier.
Typically, charge mode accelerometers are used when high
temperature survivability is required.

64. PIEZOELECTRIC SENSING MATERIALS
Two categories of piezoelectric materials that are
used in the design of accelerometers, those are
1. Quartz and
2. Polycrystalline ceramics.
Quartz is a natural crystal, while ceramics are man-
made. Each material offers certain benefits. The
material choice depends on the particular
performance features desired of the accelerometer.

65. Quartz
Quartz is widely known for its ability to perform
accurate measurement tasks and contributes heavily
in everyday applications for time and frequency
measurements.
Examples: wristwatches and radios to computers
and home appliances.

66. Quartz is naturally piezoelectric, it has no tendency to
relax to an alternative state and is considered the most
stable of all piezoelectric materials. This important feature
provides quartz accelerometers with long-term stability
and repeatability.
Also, quartz does not exhibit the pyroelectric effect (output
due to temperature change), which provides stability in
thermally active environments.
Because quartz has a low capacitance value, the voltage
sensitivity is relatively high compared to most ceramic
materials, making it ideal for use in voltage-amplified
systems.
Conversely, the charge sensitivity of quartz is low, limiting
its usefulness in charge-amplified systems, where low
noise is an inherent feature

67. Polycrystalline Ceramics
A variety of ceramic materials are used for
accelerometers depending on the requirements
of the particular application.
All ceramic materials are man-made and are forced
to become piezoelectric by a polarization process.
This process, known as “poling,” exposes the
material to a high-intensity electric field. This
process aligns the electric dipoles, causing the
material to become piezoelectric.

68. If ceramic is exposed to temperatures exceeding its range,
or large electric fields, the piezoelectric properties may be
drastically altered.
High-voltage-sensitivity ceramics that are used for
accelerometers with built-in, voltage-amplified circuits.
There are high-charge-sensitivity ceramics that are used
for charge mode sensors with temperature ranges to 400°F
(205°C).
High-temperature piezoceramics that are used for charge
mode accelerometers with temperature ranges over
1000°F (537°C) for monitoring engine manifolds and
superheated turbines.

69. Structures for Piezoelectric Accelerometers:
Three primary configurations in the structures of
Piezoelectric Accelerometers
1. Shear
2. Flexural beam and
3. Compression

70. Shear mode accelerometer
designs bond, or “sandwich,”
the sensing material between
a center post and seismic
mass.
Under acceleration, the mass causes a shear stress to be applied
to the sensing material. This stress results in a proportional
electrical output by the piezoelectric material. The output is then
collected by the electrodes and transmitted by lightweight lead
wires to either the built-in signal conditioning circuitry of ICP
sensors, or directly to the electrical connector for a charge mode
type.
1. Shear Mode

71. 2. Flexural Beam Mode
Flexural mode designs utilize beam-shaped sensing crystals, which are
supported to create strain on the crystal when accelerated. The crystal
may be bonded to a carrier beam that increases the amount of strain
when accelerated.
The flexural mode enables low profile, lightweight designs to be
manufactured at an economical price.
Generally, flexural beam designs are well suited for low frequency, low
gravitational (g) acceleration applications such as structural testing.

72. 3. Compression Mode
Compression mode accelerometers are simple structures which
provide high rigidity.
A pre-load stud or screw secures the sensing element to the
mounting base. When the sensor is accelerated, the seismic mass
increases or decreases the amount of compression force acting
upon the crystal, and a proportional electrical output results. The
larger the seismic mass, the greater the stress and, hence, the
greater the output.

73. Comparison of Piezoelectric Accelerometers

74. Piezoresistive Accelerometers
A piezoresistive accelerometer produces resistance changes in strain
gauges that are part of the accelerometer's seismic system. Piezoresistive
accelerometers have a very wide bandwidth which allows these to be used
for measuring short duration (high frequency) shock events such as crash
testing.

75. A piezoresistive accelerometer has a stable structure
composed on a silicon chip created by the micromachining
and semiconductor production technology. A mass and a
beam on which a set of the piezoresisters are created on a
silicon chip. A set of electrical bridged is formed by such
piezoresistive resisters to generate signals proportional to the
applied acceleration.

76. Features
• Measurements are possible over the wide frequency range
covering down from the ultra low up to the high frequency
as of several kHz
• Compact and light weight
• High sensitivity
• Highly acceleration resistant

77. Capacitive Accelerometers
Capacitive accelerometers, also known as vibration
sensors, rely on a change in electrical capacitance in
response to acceleration.
Accelerometers utilize the properties of an opposed
plate capacitor for which the distance between the
plates varies proportionally to applied acceleration,
thus altering capacitance.

78. Capacitive Accelerometers

79. • Most capacitive accelerometers contain built-in
electronics that inject a signal into the element, complete
the bridge and condition the signal.
• For most capacitive sensors it is necessary to use only a
standard voltage supply or battery to supply appropriate
power to the accelerometer.
• One of the major benefits of capacitive accelerometers is
to measure low level (less than 2 g’s), low frequency
(down to dc) acceleration with the capability of
withstanding high shock levels, typically 5,000 g’s or
greater.
• Some of the disadvantages of the capacitive
accelerometer are a limited high frequency range, a
relatively large phase shift and higher noise floor than a
comparable piezoelectric device.

80. Comparison of Piezoelectric,
Piezoresistive and Capacitive
Accelerometers

82. Selecting and Specifying Accelerometers
Comparison of accelerometer types

84. Typical accelerometer characteristics

85. In order to select the most appropriate accelerometer for the application,
you should look at a variety of factors.
First you need to determine the type of sensor response required.
The three basic functional categories of accelerometers are
1. IEPE,
2. Charge Mode and
3. DC responding.
The first two categories of accelerometers, the IEPE and Charge Mode type
of accelerometers, work best for measuring frequencies starting at 0.5 Hz
and above. The IEPE is a popular choice, due to its low cost, ease of use
and low impedance characteristics, .
The Charge Mode is useful for high temperature applications. There are
advantages of each design.

86. When looking at uniform acceleration, as may be
required for tilt measurement, or extremely low
frequency measurements below 1 Hz, capacitive or
piezoresistive accelerometers are a better choice.

87. These sensors may contain built-in signal
conditioning electronics and a voltage regulator,
allowing them to be powered from a 5–30 VDC
source. Some manufacturers offer an offset
adjustment, which serves to null any DC voltage
offset inherent to the sensor. Capacitive
accelerometers are generally able to measure
smaller acceleration levels.

88. The most basic criteria used to narrow the search, once the
functionality category or response type of accelerometer
has been decided, includes:
• sensitivity,
• amplitude,
• frequency range and
• temperature range.

89. Sensitivity for shock and vibration accelerometers
is usually specified in millivolts per g (mV/g) or
picocoulombs per g (pC/g).
This sensitivity specification is inversely
proportional to the maximum amplitude that can be
measured (g peak range.) Thus, more sensitive
sensors will have lower maximum measurable peak
amplitude ranges.

90. The minimum and maximum frequency range
that is going to be measured will also provide
valuable information required for the
selection process.

91. Another important factor for accelerometer
selection is the temperature range.
Consideration should be given not only to the
temperatures that the sensor will be exposed
to, but also the temperature that the
accelerometer will be stored at.
High temperature special designs are
available for applications that require that
specification.

92. Physical characteristics can be very important in
certain applications. Consideration should be given to
the size and weight of the accelerometer. It is
undesirable to place a large or heavy accelerometer on
a small or lightweight structure. This is called “mass
loading.” Mass loading will affect the accuracy of the
results and skew the data. The area that is available for
the accelerometer installation may dictate the
accelerometer selection. There are triaxial
accelerometers, which can be utilized to
simultaneously measure acceleration in three
orthogonal directions. Older designs required three
separate accelerometers to accomplish the same
result, and thus add weight and require additional
space.

93. Consideration should be given to the environment that
the accelerometer will be exposed to.
Hermetically sealed designs are available for
applications that will be exposed to contaminants,
moisture, or excessive humidity levels.
Connector alternatives are available. Sensors can come
with side connections or top connections to ease cable
routing. Some models offer an integrated cable.
Sensors with field-repairable cabling can prove to be
very valuable in rough environments.
Interfacing and Designs

94. Accelerometer mounting may have an effect on the
selection process. Most manufacturers offer a
variety of mounting alternatives. Accelerometers
can be
1. stud mounted
2. adhesively mounted or magnetically mounted.
Stud mounting provides the best stiffness and
highest degree of accuracy, while adhesive mounts
and magnetic mounting methods offer flexibility
and quick removal options.

96. https://www.iso.org/obp/ui/#iso:std:iso-iec:30128:ed-1:v1:en