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TX5600 Handbook - Vibration
 TX5600-HV-EN-01 3
TX5600 Vibration
Contents
Introduction 4
1. The Nature of Vibration 5
1.1 Vibration Frequency 6
1.2 Vibration Amplitude 7
1.3 Vibration Phase 9
1.4 Vibration Spectrum 10
1.5 Vibration Parameter 
 Conversion 10
2. Using Vibration to Evaluate
 Machine Condition 12
2.1 When to use Displacement,
 Velocity or Acceleration 12
2.2 Classification of Vibration
 Severity 14
2.3 Monitoring Acceleration 15
2.4 Monitoring Velocity 15
3. Methods of Vibration
 Monitoring 16
3.1 Piezo-electric
 Accelerometers 16
3.2 Piezo-resistive
 Accelerometers 17
3.3 Eddy Current Probes 17
3.4 Contact Displacement
 Sensor 18
3.5 Industrial Applications 18
4. Determining the Right
 Method 23
4.1 Sensitivity Range of ac Output
 Accelerometers 23
4.2 Sensitivity Range of dc
 Vibration Sensors 23
4.3 Frequency Range 24
4.4 Temperature Range 24
4.5 Mounting the Sensor 25
4.6 Where to Mount the Sensor 29
4.7 Connecting the Sensor 31
4.8 Monitoring Equipment 33
5. Typical Vibration
 Monitoring Applications 40
5.1 Underground Booster Fan
 Monitoring Utilising a
 Programmable Sensor
 Controller and the TX5633
 Vibration Sensor 40
5.2 Pump Monitoring 42
5.3 Vibration Monitoring in
 Hazardous Areas 45
5.4 Screening and Bunker
 Outfeed Monitoring 46
5.5 Conveyor Drive Monitoring 47
6. Interpreting Vibration
 Data 49
6.1 Imbalance 51
6.2 Gearmesh Problems 51
6.3 Bearing Breakdown 52
Disclaimers 53
Trademarks 53
Contact Details 53
Document History 53
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Introduction
All machines and moving mechanical devices generate a wide spectrum of 
vibration in normal use. The frequency and magnitude of vibration generated by 
each component part of a machine varies greatly, and the characteristics of each 
vibration signature changes further as a machine ages and deteriorates, resulting in 
additional mechanical stresses.
The changes in vibration characteristics can be measured and monitored to provide 
a very powerful machine condition monitoring tool. What at first appears to be a 
rather mundane subject, turns out to be a valuable technique for detailed diagnostic 
machine health monitoring that can independently evaluate the current state of 
the different parts of a machine and even predict the probability of an approaching 
system failure, so enabling corrective action to be taken before its too late.
Because of the wide and variable nature of vibration there is no standard solution 
to the best method of condition monitoring. The aim of this handbook is to set 
out a basic understanding about the cause and effects of vibration, and how to 
use this information to determine the best methods of monitoring for a particular 
application. Advise and guidance is also given about the various analytical methods 
that can be exploited for optimal performance of a monitoring system.
Several typical application examples also serve to illustrate the possibilities.
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1. The Nature of Vibration
Vibration in a structure is a result of its response to an internal or externally 
generated stimulus, causing a repeated mechanical movement.
It is generally assumed that it is vibration itself that causes damage to machines 
and structures, but this is not the whole story. Vibration induces stress into the 
materials of the structure and this ultimately leads to mechanical fatigue and 
breakdown. The degree of vibration amplitude present is dependant upon both the 
level of dynamic forces applied and the dynamic resistance of a system. A rigidly 
mounted machine will experience lower amplitude levels and much of the vibration 
will be transmitted through the floor into surrounding structures.
If a machine is installed on resilient mountings the magnitude or amplitude 
of vibration will probably increase due to the reduction in dynamic resistance 
permitted by the flexible mounting, but this will not result in any additional fatigue 
damage as the same forces are being dissipated within the machine.
Several important components of vibration are:
1. Frequency – How many times does the machine or structure vibrate per minute 
or per second?
2. Amplitude – The degree or magnitude of vibration in microns, mm/sec or g
3. Phase – How is the member moving in relation to a reference point?
4. Spectrum – Vibration presented as a frequency spectrum
5. RMS and Peak – Vibration parameters conversion
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1.1 Vibration Frequency
Frequency can be calculated from a displacement waveform, by measuring the 
time period (T) of one cycle and converting this to determine the frequency Hz. This 
is an example of a time waveform which plots vibration amplitude against time.
Checkpoint
As the waveform is a truly sinusoidal direct comparisons can be made between 
its peak-to-peak and RMS amplitudes, see Section 1.5.
 
Time waveforms are an excellent analytical tool to use when analysing gearboxes. 
The sensor can be attached close to the input or the output shaft bearing and is 
capable of revealing broken or chipped gear teeth on each revolution of the shaft or 
gearwheel. 
The illustration above shows a time waveform, showing the repeated impact of a 
broken tooth.
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The same data can be presented on a frequency baseline to analyse the fault at the 
rotational speed of the shaft or gearwheel.
The illustration above is of a frequency waveform, showing the impact at the 
rotational speed.
Imbalance, misalignment, bent shaft, eccentric rotor, and other problems will often 
produce a similar response in the frequency domain.
Time waveforms are particularly useful for low-speed shafts and gears, or 
mechanical components that oscillate backwards and forwards. They are often the 
only analytical tool which can be effectively used at lower rotational speeds or cycle 
times.
1.2 Vibration Amplitude
Vibration amplitude is a measure of magnitude of vibration and can be expressed in 
terms of displacement, velocity or acceleration.
1.2.1 Displacement
Displacement is a measure of the total travel of a measurement point, between 
the two extremities of vibration and is usually expressed as a distance in microns. 
When a machine is being subjected to excessive dynamic stress at very low 
frequencies, displacement may be a good indicator of vibration severity since the 
machine or structure, may be flexing too much, being subjected to impacts, or 
simply being flexed too far.
1.2.2 Velocity
The velocity of vibration is a measure of the speed at which a mass is moving or 
vibrating during its oscillations, the faster a machine flexes, the sooner it will fail in 
fatigue. Vibration velocity is directly related to stress fatigue.
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When an oscillating mass is suspended from a spring the velocity of the mass 
reaches its maximum value, or peak, at the mid point, the point at which the mass 
is fully accelerated (acceleration is zero). It now begins to decelerate in the second 
half of the cycle. Velocity is expressed as millimetres per second (mm/sec).
Checkpoint
In reality, vibration response is not usually a pure sine wave and an analyser is 
invariably used to capture peak velocity.
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1.2.3 Vibration Acceleration
When a component on a machine vibrates, it experiences acceleration since it 
continually changes speed as it oscillates from one peak to the other. Acceleration 
is greatest at the instant when velocity is at its minimum, at the point where the 
mass has decelerated to a stop and is about to begin accelerating again in the 
opposite direction.
Acceleration is the rate of change in velocity and is normally expressed in units of 
g, where 1 g = 9.81ms–2.
The greater the rate of change of velocity, the greater will be the forcesand 
stresses on the machine due to the higher acceleration. At high frequencies, the 
excessive force can reach a point where the bearing lubrication can break down 
allowing the metal surfaces of bearings to come into contact, potentially causing 
catastrophic failures. These forces are directly proportional to acceleration (force = 
mass x acceleration) and acceleration mode is the parameter most often employed 
for machine protection.
1.3 Vibration Phase
Phase is a relative expression of how one part of the machine is moving or vibrating 
with respect to another part, or to a fixed reference point on the same machine.
Phase is mostly used as an in depth analytical tool, when initially setting up a 
machine, to ensure it has been mounted and aligned correctly. It is rarely used for 
continuous monitoring of machine condition.
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1.4 Vibration Spectrum
This frequency domain presentation of a time waveform is called a spectrum 
analysis and is sometimes referred to as a vibration signature.
1.5 Vibration Parameter Conversion
It is possible to convert from one amplitude parameter to another, using either 
electronic conversion or a mathematical formula.
Electronics or processing software, can also convert between RMS (root mean 
square), peak and peak-to-peak. The illustration below shows the relationship 
between RMS, peak and peak-to-peak, for a purely sinusoidal waveform.
Peak-to-peak
x
Peak
x
RMS
x
Average
x
Peak-to-peak = 1 2 2.828 3.142
Peak = 0.5 1 1.414 1.571
RMS = 0.354 0.707 1 1.5
Average = 0.318 0.636 0.9 1
eg. peak-to-peak x 0.5 = peak
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Most vibration waveforms are not sinusoidal in practice and peak and peak-to-peak 
readings become less useful and RMS assessment is most often used.
RMS amplitude gives a more accurate representation of the energy within the 
vibration, and hence the force that will be exerted.
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2. Using Vibration to Evaluate Machine Condition
The causes of vibration in rotating machinery are numerous. Some may simply 
originate from machine set-up problems:
• Imbalance of system
• Misalignment of shafts
• Bent or distorted shafts
• Loose mechanical components
• Ineffective or inadequate mounting structures
Operational dynamic problems can also be identified:
• Bearing deterioration
• Mechanical components becoming loose or detached
• Build up of debris on fan blades and other rotating parts
• Chipped fan blades and rotors
• Geartooth wear and breakage
• Loss of lubrication
If these problems are left unattended, catastrophic consequences can result. 
These can vary from machine downtime, lost whilst a seized bearing is replaced, or 
the complete disintegration of a fan when the out of balance causes the impeller 
blades to impact on the casing.
By utilising vibration monitoring, an early warning of impending mechanical 
failure can be obtained. Further analysis of the vibration by a skilled engineer 
using frequency analysis enables the problem to be pinpointed and preventative 
maintenance can be implemented at a convenient time.
2.1 When to use Displacement, Velocity or Acceleration
Movement displacement is an obvious indicator of how much a machine is 
vibrating, but the actual severity of vibration is also a feature of the frequency 
of vibration. The higher the frequency, the greater will be the energy expended 
for a given level of displacement. The vibration velocity of a measurement point 
increases as the displacement and or velocity increases.
Conversely, if a machine is turning or oscillating slowly with the same amount of 
displacement, then the vibration severity will be proportionally lower.
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This can be demonstrated by a series of vibration severity characteristics generally 
applicable for a horizontal rotating machine.
Vibration severity categories expressed in terms of velocity, are defined for various 
combinations of displacement and frequency.
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2.2 Classification of Vibration Severity
The standard general vibration severity chart is used to assess machine condition. 
However this is intended to be used as a guide and not an absolute reference. The 
standard of installation of the equipment and the general maintenance of it will 
have a significant effect on the vibration levels seen.
Although the chart can be used as a general indication, trending of the vibration 
levels against time will give a more accurate indication of the change in condition of 
the machine. On fixed monitoring equipment, warning and alarm levels can be set 
to be within the Good condition zone.
• Class I: Individual parts of engines and machines, integrally connected with the 
complete machine
• Class II: Medium or large machines, typically electrical motors with 
15 to 75 KW output
• Class III: Large prime movers and other large machines with rotating masses 
mounted on rigid and heavy foundations up to about 300KW output
• Class IV: Large prime movers and other large machines or turbines with 
rotating masses mounted on foundations which are relatively soft
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2.3 Monitoring Acceleration
 Measurement of acceleration is most widely employed when the 
 vibration frequency of a machine is in excess of 1 kHz. Acceleration 
 must be assessed in conjunction with vibration frequency to analyse the 
 severity of vibration. High levels of acceleration combined with higher 
frequency is indicative of high vibration energy being dissipated and the various 
combinations can be classified.
2.4 Monitoring Velocity
 Vibration velocity monitoring is relatively independent of vibration 
 frequency at lower levels of vibration. Consequently this method is 
 generally adopted for monitoring the condition of slowly rotating or 
 oscillating machines in the 10 Hz to 1 kHz range.
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3. Methods of Vibration Monitoring
A sensing element, mounted directly on to the machine, generates an output signal 
that is proportional to the amplitude and frequency present in the machine. The 
output signal format will be dependent upon the type of sensor being used.
3.1 Piezo-electric Accelerometers
The piezo-electric accelerometer is widely used for industrial vibration 
measurement. Its construction consists of a crystal of piezo-electric material 
to which is attached a seismic mass. When the crystal is stressed in tension or 
compression during vibration, it generates an electrical charge which is proportional 
to the acceleration level it is experiencing. Internal circuitry converts this signal into 
a voltage or current for transmission to data collectors or process control loops.
This robust device has no moving parts and offers long term stability and reliability. 
It has very wide frequency and dynamic ranges and the output signals can be 
electronically integrated to give velocity and displacement values. Accelerometers 
tend to be a more economical solution than the alternative devices and are available 
for a wider range of arduous applications eg. high temperature environments, 
submersible operation and high tolerance of corrosive media.
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3.2 Piezo-resistive Accelerometers
Strain gauge technology is employed to monitor the force exerted by a vibrating 
mass on to a beam. The frequency range of this device is lower than piezo-electric 
versions, but has the advantage of being able to monitor low frequency vibration 
down to static or dc acceleration levels.
Because of its ability to monitor low levels of acceleration, the piezo-resistive 
accelerometer is not as robust as piezo-electric devices which limit its application 
and the costis usually higher. 
3.3 Eddy Current Probes
Eddy current probes monitor displacement using a non-contacting or proximity 
method. The eddy current probe is widely used for measuring distances on static 
and rotating machines. Both the ac vibration and dc gap can be measured by this 
non-contact method. The simplicity of the probe lends itself to being used in harsh 
conditions and performs best in very large machines having relatively high levels of 
displacement.
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3.4 Contact Displacement Sensor
There are a number of different types of contact displacement sensors. The most 
commonly used version being the LVDT type.
The use of this type of sensor, is usually limited to specialist applications, and 
relatively low vibration frequencies where direct contact with the surface being 
monitored can be accommodated.
3.5 Industrial Applications
The overall operating characteristic of piezo-electric sensors are ideally suited to the 
demanding requirements of heavy industry. They are capable of working reliably 
for long periods in extreme environments with minimum maintenance, and two 
basic versions are available for use with a range of monitoring devices to suit any 
application.
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3.5.1 ac Output Signal - TX5633
The output signal is a direct millivolt representation of the actual vibration across 
the complete frequency spectrum range of the sensor. Individual frequency bands 
relating to discrete components on the machine can be separated and used by a 
suitable monitoring device to analyse specific faults and changing conditions. A low 
frequency band selected at the rotational speed of the machine shaft will highlight 
out of balance problems, debris build up or loose mechanical components.
If a second higher frequency band is also defined, then accurate data relating 
to bearing condition can be monitored or trended to give advanced warning of 
impending failure as a result of a worn or cracked bearing.
This method of vibration monitoring provides very accurate condition data about 
specific parts of the machine, particularly when it is used in conjunction with 
monitoring devices that can effectively analyse the data.
This range of vibration sensors is available with an ac output voltage compliant with 
industry standard ICP interface. This provides for precision vibration measurement 
for machine condition monitoring.
These sensors feature:
• ac output signal for discreet vibration 
frequency monitoring 
RMS indication of acceleration, velocity 
or displacement
• Programmable function and setpoint 
alarms when used with: 
TX9137 Programmable Trip Amplifier or 
TX9042/4 Programmable Sensor Controller
• High integrity vibration monitoring for 
generators, pumps, compressors, turbines 
and engines
• Intrinsically Safe versions available for 
hazardous areas
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Technical Details
Sensing principle Piezo-electric accelerometer
Frequency range 1 Hz to 10 kHz
Sensitivity range 100 mV/g
Linearity +/- 1%
Temperature limits -55°C to +110°C
Supply voltage 12 V dc
Material Stainless steel
Protection classification IP67
Mounting M8 x 8 mm mounting stud or
Quickfit bush
Ex certification EEx ia I
Options Cable length to specification
MS plug and socket connection
Order Reference
Vibration Sensor - ac
Intrinsically Safe 
Group I
TX5633
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3.5.2 dc Output Signal - TX5634 to TX5639
This very similar to the ac output vibration sensor but with an additional built in 
signal conditioning stage. The raw ac signal of the complete frequency spectrum is 
averaged into an industrial standard 4 to 20 mA signal, so that low overall vibration 
levels will generate a 4 mA signal and this will increase linearly as the overall level 
of vibration increases up to the full scale value of 20 mA.
Sensors for use on low speed machines, up to about 1 kHz, are calibrated in terms 
of acceleration in a choice of measuring ranges from 2 g up to 100 g. Higher speed 
machines in the 1 kHz to 10 kHz band are best assessed using sensors calibrated in 
terms of velocity and there is a choice of ranges to suit various applications from 
0 up to 100 mm/sec.
This type of sensor will accurately monitor the mean level of vibration across the 
complete frequency spectrum and is very easy to interface with standard industrial 
control loops. Any general deterioration of the machine condition will show up as a 
general and overall increase in the level of vibration and this can be used for display 
purposes or to operate alarm warnings and control devices. This particular sensor 
is equally useful for indicating that a machine is actually running as it should be. For 
example, vibration will be absent on a vibrating screen that has failed, so an alarm 
warning can be initiated.
This range of vibration sensors provides a 4 to 20 mA output proportional to a fixed 
range of either velocity or acceleration. This allows the sensor to be connected to a 
PLC or other standard monitoring equipment.
These sensors feature:
• Programmable function and setpoint 
alarms when used with: 
TX9131 Programmable Trip Amplifier or 
TX9042/4 Programmable Sensor Controller
• High integrity vibration monitoring for 
generators, pumps, compressors, turbines 
and engines
• Intrinsically Safe versions available for 
hazardous areas
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Technical Details
Sensing principle Piezo-electric accelerometer
Frequency range 1 Hz to 10 kHz
Linearity +/- 1%
Operating temperature -40°C to +60°C
Analogue output 4 to 20 mA
Supply voltage 10 to 32 V dc
Material Stainless steel
Protection classification IP67
Mounting M8 x 12 mm mounting stud or
Quickfit bush
Ex certification EEx ia I
Options Cable length to specification
M12 plug and socket connection
Order Reference
Vibration Sensor - Acceleration
Intrinsically Safe 
Group II
General Purpose
Intrinsically Safe 
Group I
TX5634 TX5635 TX5636
Vibration Sensor - Velocity
Intrinsically Safe 
Group II
General Purpose
Intrinsically Safe 
Group I
TX5637 TX5638 TX5639
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4. Determining the Right Method
Several factors need to be considered when specifying the characteristics of the 
most suitable vibration sensor to achieve the best performance for a particular 
application. This is largely dependent upon the type of machine being monitored 
and the way it functions. The method of mounting the sensor on to the machine 
is also important and a determination must be made about the type of data that is 
required from the sensor to drive the chosen monitoring equipment.
4.1 Sensitivity Range of ac Output Accelerometers
The sensing element of an ac accelerometer generates an ac voltage output signal, 
the amplitude of which, is directly proportional to the actual acceleration being 
experienced by the device as it vibrates.
To take the example of a sensor that has a sensitivity of 100 mV/g, this means that 
if 0.1 g is being measured by the sensor at a particular frequency, it would give an 
ac output signal of: 0.1 x 100 = 10 mV. The appropriate full scale output range can 
therefore be selected to match the input range of the monitoring equipment being 
used. However, the severity of vibration is also a function of the frequency and 
this factor should be carefully analysed in conjunction with the standard vibration 
severity tables.
4.2 Sensitivity Range of dc Vibration Sensors
In the case of vibration sensors having a standard 4 to 20 mA dc output signal, 
the collective vibration generated by the machine is averaged across the complete 
frequency range into an analogue dc signal that is linearly proportional to the 
general overall level of vibration.
The output signal can be calibrated in termsof acceleration or velocity. Acceleration 
is most widely used with higher range vibration frequency in excess of 1 kHz. 
Velocity measurement is generally more efficient when monitoring slow moving 
machinery or shafts operating from 10 Hz up to a maximum of 1 kHz.
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4.3 Frequency Range
The frequency range specified for a vibration sensor is the frequency band over 
which the sensor can effectively operate, and still provide a consistent output 
signal. It is important to ensure that the operating frequency range of the machine 
being monitored falls within the capability of the sensor.
4.4 Temperature Range
This is the minimum and maximum temperature limits that the sensor can 
withstand without significantly affecting its response capabilities. This is an 
important consideration when using the sensor on high temperature equipment or 
in hot climatic conditions.
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4.5 Mounting the Sensor
Piezo-electric sensors measure vibration mainly in line with the axis of monitoring 
so it is important that the sensor is installed at the optimum position on the 
machine. A firm anchor is also essential as incorrect mounting will produce 
inconsistent data.
There are five commonly used sensor mounting methods and each one has a 
maximum operating frequency that can be monitored.
Maximum Operating 
Frequency
Resonant Frequency
Stud mount 16 kHz 30 kHz
Quickfit stud mount 6 kHz 10 kHz
Magnetic mount 7.5 kHz 12 kHz
Handheld 800 Hz 1.5 kHz
Adhesive mount 9 kHz None
Each mounting method also has its own resonant frequency and working in this 
envelope of vibration should be avoided for best accuracy of response.
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4.5.1 Stud Mount
Stud mounting is used for permanently mounted sensor applications. Sometimes, 
an adhesive will be used in combination with mounting thread to prevent the 
sensor from losing its torsion under vibration conditions. Stud mounting is not 
always practical for all applications, but it is the preferred method.
In order for the vibration sensor to reproduce precisely the vibration generated by 
the machine under surveillance, it is imperative that its mounting face, in effect, 
becomes a solid part of the structure. The sensor mounting face should see a flat 
surface at the machine interface, any surface irregularities will compromise the 
correct transmission of vibration.
Avoid the common pitfalls below:
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4.5.2 Quickfit Stud Mount
Quickfit stud mounts are also extensively used for collecting data with portable 
instruments. Repeatability of readings within its acceptable range is good, making it 
suitable for use with most data collectors.
4.5.3 Magnetic Mount
Magnetic mounts are generally used with portable diagnostic instruments when 
data collecting and will produce repeatable data over its operating frequency range.
An alternative to magnetic or portable mounts is to bond a Quickfit bush mount 
onto the machine.
4.5.4 Handheld
This is the least acceptable method of mounting and is only really usable on 
vibration frequencies below 1 kHz. 
A handheld probe is of use when other mounting options cannot be used.
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4.5.5 Adhesive Mount
Adhesive mounts should be utilised as an alternative to stud mounting where a 
stud cannot be fitted. Great care should be taken in preparing the surface when 
using an adhesive, to ensure a permanent bond, because a bad joint will work loose 
over a period of time.
An alternative to magnetic or portable mounts is to bond a Quickfit bush mount 
onto the machine.
The type of adhesive must be appropriate for the materials and the environment 
in which it is to be used. The adhesive must also provide a rigid base. Soft set 
adhesive will cause the higher frequencies to be absorbed.
4.5.6 Wiring
It is also recommended that the sensor cable is looped and then tied with a cable 
tie to the main body in order to avoid excessive wear.
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4.6 Where to Mount the Sensor
In order to ensure that vibration problems are diagnosed correctly, it is essential 
that information received from sensors is representative of the actual vibration 
on the machine component being monitored. Correct selection of the type of 
sensor for the vibration being monitored is imperative, but equally important is the 
mounting location of the sensor on the machine.
When monitoring bearings, the sensor should be located as close to the source 
of vibration as possible. This should be within the load zone of the bearing and is 
particularly important where high frequency components of vibration are being 
monitored.
Ideally, horizontal and vertical measurements should be taken. However, where 
cost is critical, a compromise solution of fitting the sensor at 45° to the horizontal 
can be effective.
The sensor should be mounted such that the sensing axis of the sensor passes 
through the centre of the shaft and as close as possible to the shaft centre line.
Readings taken on foundations adjacent to the machine are not representative of 
shaft and bearing vibration and should only be used when structural vibrations are 
being monitored.
Care should be taken to ensure that the sensor is mounted on a substantial 
structural part of the machine, such as the motor casing. Avoid mounting on thin 
sheet metal structures such as outer casings as this can lead to distortion of the 
data acquired.
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Fitting the sensor to one of the mounting feet of the machine will generally give 
best results for axial vibration measurement if locations near to the rotating shaft 
are inaccessible.
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4.7 Connecting the Sensor
Because of the low level of signal produced by most vibration sensors, it is 
important that good electrical practice is followed in cabling the sensor, on fixed 
installations.
Accelerometers are usually fitted with screened PVC cable encased in an 
overbraided stainless steel sheath. This offers excellent protection for the arduous 
environment in which vibration sensors are often used. Long lengths can be difficult 
to control and movement of the cable itself can contribute to vibration signals.
It is recommended that the cable is looped where possible, and secured to the 
sensor. This also avoids excessive wear and stress at the cable/sensor junction.
The cable can be terminated at a local junction box or sensor versions are available 
with an integral plug and socket connector.
In order to avoid electrical pickup through the case of the sensor from the machine 
being monitored, the machine should be properly earthed in compliance with local 
regulations. If a good earth is not possible, the sensor and the cable overbraid 
should be electrically isolated from the machine.
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The screen of the cable should be connected to earth at the monitoring equipment. 
It should not be earthed at the motor. The cable overbraid should be left 
unconnected.
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4.8 Monitoring Equipment
The output signal derived from vibration sensors can be interfaced with a variety of 
monitoring devices to provide simple alarm functions or on line condition analysis 
of machinery systems. ATEX certified options are also available for use in hazardous 
areas.
The data presented by the vibration sensors falls into two basic categories:
1. An industrial standard 4 to 20 mA signal that is an overall dc average of the 
complete spectrum of vibration being generated by the machine, this is useful 
for overall trend analysis and general alarm level monitoring.2. Accelerometers that give an ac voltage representation of the actual vibration 
across the frequency spectrum being monitored in accordance with the 
industry standard ICP interface. This can be a powerful diagnostic tool enabling 
specific frequency bands to be monitored and assessed in exclusive terms.
Each type of sensor will require an appropriate monitoring system for optimum 
performance, and power to drive the sensor will be provided by the selected 
control and monitoring unit.
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4.8.1 Programmable Trip Amplifier
These instruments can be used to provide a readout of vibration level and provide a 
relay output contact, to alarm when levels exceed a pre-determined value.
There are versions to accept the ac signal from vibration sensors as well as the 
conditioned output from 4 to 20mA sensors.
Total programming versatility in a single unit with direct fingertip selection of all 
input and output control and display functions.
• Easy to operate menu 
programme
• Large digital LCD screen with 
function display and input 
signal display
• Analogue or frequency inputs
• Dual set point, relay output
• 4 to 20 mA repeater signal
• Intrinsically Safe versions 
available for hazardous areas
• Specific frequency boards can 
be specified when using ac 
accelerometer sensors for 
specific monitoring of low or 
high frequency vibration factors 
such as shaft rotational speed 
or high frequency bearing noise
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Technical Details
Temperature limits -5°C to +50°C
Display LCD dot matrix, 16 characters
Supply voltage 12 V dc (nominal)
Input signal capability Current (4 to 20 mA) 
ac Vibration (1 to 20 kHz)
Output relays 2 with programmable set points, time delay 
hysteresis, rising/falling, latching/pulsing, power 
on delay, configurable time delay
Signal update period 0 to 120 seconds
Set point adjustment 0 to 99%
Hysteresis adjustment 0 to 99%
Information display Menu of standard units (g, mm/s, ft/s, etc.)
programmable scale/zero, signal bar graph, 
set point value display, signal tendency, alarm 
indicators, signal line monitor, peak/low indicator.
Certification EEx ia I
Options Repeater output signal (choice of 0.4 to 2 V, 
4 to 20 mA or 5 to 15 Hz)
DIN rail mount (IP20), Panel mount (IP65) or 
Rack mount (IP20)
Order Reference
Programmable Trip Amplifier
4 to 20 mA ac
TX9131 TX9137
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36 TX5600-HV-EN-01
4.8.2 Programmable Trip Amplifier
Monitoring up to eight channels of vibration or a combination of condition 
monitoring sensors. Datalogging and communication facilities allow for trending of 
vibration. This simplifies monitoring of machine deterioration.
Monitors any combination of eight analogue sensors or up to sixteen On/Off digital 
inputs or frequency inputs.
These instruments feature:
• Menu operated function selection - scale, 
units and offset
• Four programmable output relays
• Simultaneous display of input signal levels
• Signal tendency display
• Signal bar graph
• Peak/low data display
• Datacomms for RS232/RS485. TTL digital 
(MODBUS)
• 26,000 point data logging
• Intrinsically Safe versions 
available for hazardous areas
• Specific frequency boards can 
be specified when using ac 
accelerometer sensors for 
specific monitoring of low or 
high frequency vibration factors 
such as shaft rotational speed 
or high frequency bearing noise
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TX5600 Handbook - Vibration
 TX5600-HV-EN-01 37
Technical Details
Mounting DIN rail, front of panel or 19” rack
Display LCD dot matrix, 20 characters x 4 lines. Eight 
way simultaneous display with individual channel 
close-up facility
Supply voltage 12/24 V dc at 120 mA
Input signal capability Current (4 to 20 mA), voltage (0 to 10 V), 
thermocouple (type J or K), platinum resistance 
(PT100), bridge (0.1 mV/V to 100 mV/V), digital 
(on/off), frequency (0.1 Hz to 5 kHz), ac vibration 
(1 to 20 kHz)
Set points 2 per channel, programmable set point 
level, time delay, hysteresis, rising/falling, 
latching/pulsing, power on delay
Output relays 4, with configurable function grouping
Set point adjustment 0 to 99%
Hysteresis adjustment 0 to 99%
Information display Menu of 30 standard engineering units, (bar, 
m/s, rpm, etc), programmable scale/zero, signal 
bar graph, signal tendency, signal fault alarm, 
peak/low data retention, channel reference text 
entry
Data log 26,000 point data log event recording on each 
channel
Certification EEx ia I
Datacomms RS232, RS485. TTL digital
Order Reference
Programmable Trip Amplifier
Group I - Mining General Purpose
TX9042 TX9044
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38 TX5600-HV-EN-01
4.8.3 Distributed Monitoring
Multi channel distributed condition monitoring across a wide area network with 
SCADA base station.
• Bus expandable to 256 channels of I/O
• Configurable input signals and output drivers
• Programmable sensor response functions
• Programmable logic control functions
• Data logging
• Datacomms for distributed systems
• Intrinsically Safe for hazardous area 
operation
• Sensor input signal values 
Individual or multisensor display with 
signal bargraph trending and text entry 
for sensor duty
• Control output signal status - individual 
or simultaneous display of output 
function and text entry for control duty
• Data history - data storage of peak/low 
values and graphical trending. Data 
logging of sensor data and output events 
with time, date and identification
• Sensor signal function programming 
Characterisation of sensor response 
including: rising/falling signal, hysteresis, 
scaling, units, offset, damping, sample 
rate and fault monitoring
• Datacomms - proprietary Datacomms 
for distributed monitoring and control 
systems with conventional or optic fibre 
transmission - MODBUS • SAP • Ethernet
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TX5600 Handbook - Vibration
 TX5600-HV-EN-01 39
4.8.4 System Analysis
It is not always possible to determine the most appropriate type of vibration 
monitoring that is required on a machine, or it can be difficult to asses the actual 
vibration levels that are present. It is sometimes necessary to seek specialist 
advice for a specific system analysis using high accuracy vibration measuring 
instruments.
This service can often form an important part of an on going structured preventative 
maintenance programme.
FFT Programmable Data Collectors
FFT analysers enable vibration to be monitored in the frequency spectrum, 
simplifying diagnosis of machine problems.
However, due to cost, these instruments are rarely used for fixed installations. They 
are usually used as portable instruments to diagnose problems found by overall 
vibration level analysis instruments.
Real-Time Spectrum Analysers
Because of the processing power required, most FFT analysers work on stored 
vibration readings.
If real-time monitoring is required, a real-time spectrum analyser should be used. 
However, their cost and physical size usually prohibits use in all but exceptional 
circumstances.
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40 TX5600-HV-EN-01
5. Typical Vibration Monitoring Applications
5.1 Underground Booster Fan Monitoring Utilising a 
 Programmable Sensor Controller and the TX5633 
 Vibration Sensor
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TX5600 Handbook - Vibration
 TX5600-HV-EN-01 41
In the illustration above each sensor signal feeds two independent input channels 
on the controller. One channel monitors velocity (in mm/s) in the frequency range 
10 to 500 Hz. The second channel is configured to monitor acceleration in the 
frequency range 1 kHz to 20 kHz.
The fan is running at 1500 rpm giving a fundamental of 25 Hz.
After the fan has been given time to run in, the vibration levels on each channel 
should be monitored using an FFT analyser to ensure that there are no vibration 
levels of concern.
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42 TX5600-HV-EN-01Velocity is used to monitor out-of-balance on the fan. This can be due to a number 
of causes:
• Misalignment of the shaft
• Imbalance of the blades
• Dust build-up on the blades
• Chipped or broken blades
Acceleration is used to monitor bearing breakdown. This can be a result of a 
number of conditions, such as lack of lubrication or long term wear and tear.
By looking at the trend of velocity and acceleration, the deterioration of the fan, 
especially with respect to its bearings, can be monitored.
As well as monitoring excess vibration levels, the sensors will confirm that the 
fan is running. A moderate level of vibration, indicates a healthy fan, running at its 
normal speed. Lack of vibration would indicate a signal fail, or stationary fan.
5.2 Pump Monitoring
In this application, two TX5633 sensors are mounted on the outlet end of the 
pump, one vertical and one horizontal, to monitor: out-of-alignment, mounting 
movement or loose fixings.
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TX5600 Handbook - Vibration
 TX5600-HV-EN-01 43
The TX5633 sensors are connected to two channels of the Programmable Sensor 
Controller which is set-up to monitor velocity in the range 10 to 500 Hz. The pump 
is rotating at 3000 rpm giving a fundamental frequency of 50 Hz.
Alarm levels on the Programmable Sensor Controller are set up according to 
BS7854 Part 1, (ISO10816-1) to monitor vibration severity.
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44 TX5600-HV-EN-01
As the Programmable Sensor Controller has spare channels available, temperature 
and pressure monitoring on the pump can easily be accommodated using simple 
PT100 probes and pressure sensors.
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TX5600 Handbook - Vibration
 TX5600-HV-EN-01 45
5.3 Vibration Monitoring in Hazardous Areas
When the machinery to be monitored is in a hazardous area, certified safe 
equipment needs to be used. TX5630 Vibration sensors are certified, Intrinsically 
Safe, for use in Group II hazardous areas. However, Trolex monitoring equipment is 
intended for mounting in the safe area.
In order to connect to the sensors in the hazardous area, zener safety barriers or 
isolators need to be used between the sensors and the monitoring equipment. The 
diagrams below give typical barrier and isolator options.
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46 TX5600-HV-EN-01
5.4 Screening and Bunker Outfeed Monitoring
Vibratory screens are used for the grading of product in many mining and quarrying 
applications. Product is introduced onto a vibrating sieve and small product passes 
through whilst large product is screened to the next stage.
Vibrating pans are used on the outfeed to ensure that product does not block the 
outfeed chutes. 
A Trolex TX5630 Vibration Sensor mounted on the vibratory screen, can monitor the 
operation and condition of the screen, when connected to a Programmable Sensor 
Controller. Upper and Lower alarms can monitor that the screen is running correctly 
and that vibration levels are not excessive. By trending vibration levels, deterioration 
in the condition of the screen and its mounts can be monitored.
Similarly, the vibrating pans on the outfeed can be monitored for both operation and 
excessive wear.
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TX5600 Handbook - Vibration
 TX5600-HV-EN-01 47
5.5 Conveyor Drive Monitoring
A conveyor is the backbone of any product clearance system and a breakdown 
of this is likely to be costly. Utilising vibration monitoring equipment, the plant 
engineer can obtain an early indication of impending motor and gearbox failure. 
Temperature monitoring can also be utilised to save catastrophic failure by 
interlocking an excessive temperature alarm setpoint with the motor drive control.
The following diagram shows how the vibration sensors and temperature sensors 
connected to a Programmable Sensor Controller and how this could be used to 
disable the conveyor under high temperature conditions or excessive vibration.
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48 TX5600-HV-EN-01
NAMUR sensors can be used to indicate conveyor speed and belt slip, by 
monitoring the speed of both the motor and an idler wheel. If the temperature 
inputs are programmed to latch one of the output relays when over temperature 
occurs, the output relay could be interlocked with the conveyor stop circuitry to 
lockout the conveyor. The latched relay would then have to be manually reset before 
attempting to restart the machine.
An input from the conveyor drive contactor can give confirmation that the conveyor 
is running.
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TX5600 Handbook - Vibration
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6. Interpreting Vibration Data
An example is given below to demonstrate how vibration how vibration can be 
used to monitor bearing and gearmesh deterioration and imbalance on a ventilation 
fan. 
Ventilation fans are used in critical areas such as underground mining and 
tunnelling, where natural ventilation is not sufficient to either dilute noxious/
explosive gases or to ensure a sufficient supply of oxygen.
There are 3 areas of interest in monitoring vibration on the above installation.
Although these areas are not always as discreetly defined as shown here, they 
have been separated for the purposes of this example.
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TX5600 Handbook - Vibration
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6.1 Imbalance
 Imbalance occurs because the machine is not perfectly balanced about 
 the shaft centre line. This can be caused during manufacture, installation 
 or during operation (eg. debris build-up on a fan blade).
Imbalance will occur at the rotational frequency of the fan. So on a fan rotating at 
1500 rpm, imbalance will occur at 25 Hz. As the imbalance increases, it will be seen 
as increase in the vibration signal at 25 Hz. This will require a monitoring instrument 
capable of displaying the signal in the frequency domain 
(eg. FFT analyser).
If a broadband alarm monitor, such as the Programmable Sensor Controller is used, 
with a fixed, low pass filter then the general overall level of vibration will be seen to 
increase. This can be compared to an alarm set-point, as suggested by BS7854 
Part 1. This alarm indication would suggest that a spectrum analyser should be 
employed to define the fault more specifically.
6.2 Gearmesh Problems
 Vibration due to the gear teeth will be seen at the rotational frequency 
 multiplied by the number of teeth. So, on a machine with rotational 
 frequency 1500 rpm and 30 teeth on the wheel, the fundamental 
 vibration frequency is about 750 Hz. As the teeth start to deteriorate, 
the amplitude of the vibration, at the 750 Hz fundamental, will increase. This would 
easily be picked up with an instrument such as an FFT analyser.
An alarm instrument such as a Programmable Sensor Controller, could also be 
used to indicate that the level of vibration, around the frequency of interest, has 
increased.
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52 TX5600-HV-EN-01
6.3 Bearing Breakdown
 Bearing noise, due to imperfections in the bearing, will start at high 
 frequency (>1 kHz). Bearing deterioration can be caused by:
• Poor quality of the bearing
• Inadequate lubrication
• Contaminated lubrication
• Poor installation
As the bearing starts to deteriorate, larger imperfections occur, increasing the 
amplitude of the vibration and at the same time reducing the frequency of the 
vibration. Over time, the signal will change as shown in the illustration below.
A Programmable Sensor Controller can be used to monitor the increase in 
broadband vibration, whilst disregarding the change in frequency.
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Disclaimers
The information provided in this document contains general descriptions and 
technical characteristics of the performance of the product. It is not intended as 
a substitute for and is not to be used for determining suitability or reliability of 
this productfor specific user applications. It is the duty of any user or installer to 
perform the appropriate and complete risk analysis, evaluation and testing of the 
products with respect to the relevant specific application or use. Trolex shall not be 
responsible or liable for misuse of the information contained herein. If you have any 
suggestions for improvements or amendments, or find errors in this publication, 
please notify us at marketing@trolex.com.
No part of this document may be reproduced in any form or by any means, 
electronic or mechanical, including photocopying, without express written 
permission of Trolex. 
All pertinent state, regional, and local safety regulations must be observed 
when installing and using this product. For reasons of safety and to help ensure 
compliance with documented system data, only Trolex or its affiliates should 
perform repairs to components. 
When devices are used for applications with technical safety requirements, the 
relevant instructions must be followed. 
Trademarks
© 2014 Trolex® Limited. 
Trolex is a registered trademark of Trolex Limited. The use of all trademarks in this 
document is acknowledged.
Document History
Issue 01 19 June 2014 Original publication of this document
Contact Details
Trolex Ltd, Newby Road, Hazel Grove, Stockport, Cheshire, SK7 5DY, UK
+44 (0) 161 483 1435 sales@trolex.com 
www.trolex.com