10 Tips to Choose the Best Vibration Analyzer

digivibe-vibration-analyzer

10 Tips to Choose the Best Vibration Analyzer

 

< 10 Tips for Vibration Analysis Vibration Analyzers >

 

Finding the best Vibration Analyzer for your application can be quite tricky. Moreover, if you don’t know how to identify the functionality that you need.

So, what is a vibration analyzer? And more importantly, what do I need to know before I chose one. Take some time to read this post and find out your best option.

 

What is a Vibration Analyzer?

A Vibration analyzer is an instrument used to measure, store and diagnose the vibration produced by machinery. It uses FFT based tools to display the magnitude of the vibration as it varies over the frequency. The primary use is to identify and predict faults in industrial machines as well as the causes that originate them.

 

The Best vibration analyzers are capable of saving measurements and organizing them for future analysis, thus, generating trends for each machine. These instruments are also known as data collectors.

 

How does a Vibration Analyzer work?

A Vibration Analyzers is basically a computer that records vibration through one or more accelerometers. Vibration motion, inside the accelerometer, is converted to an electrical current proportional to the acceleration. This signal is stored and processed in the computer to display its magnitude versus frequency with algorithm called FFT (Fast Fourier Transform).

 

1. Features of a Vibration Analyzer

When choosing a vibration analyzer, the following are the main features to focus in:

  1. Number of input channels
  2. Lines of resolution
  3. Resolution
  4. Frequency range
  5. Additional functions like Balancing, ODS (3D simulations)
  6. Types of sensors that it can handle
  7. Portability
  8. Technical support and spare parts
  9. Price and Annual costs (if applied)

 

Vibration Analysis Equipment

Portable Vibration Analyzer – Digivibe®

Digivibe M30 Vibration Analyzer is an advanced and portable system designed to analyze machinery vibrations individually. It is capable of plotting spectra in the field with up to 1,638,400 lines of resolution. Additionally, Digivibe M30 is able to perform dynamic balancing on site for 1 and 2 planes.

  • Frequency range: 1 Hz – 14 kHz
  • Resolution lines: 1,638,400
  • Simultaneous input channels: 4
  • Balancing capability: Yes
  • 3D simulations (ODS)
  • Database of bearings and Gears
  • Compatibility with the cloud
  • Compatibility with mobile devices: Yes

Learn More ->

Wireless Vibration Analysis Equipment

Wireless Vibration Analyzer – Wiser 3X®

Vibration Analyzer – Wiser 3X is a triaxial accelerometer that has the Wiser Vibe and Digivibe application compatibility for Vibration Analysis. It is the latest generation of wireless accelerometers, capable of sending 4 vibration channels in real time for X, Y and Z axes as well as an additional reference channel for phase comparison. In addition to being ultra-portable, Wiser 3X incorporates start and stop functionality in the same power button, to save valuable time during data collection.

  • Frequency range: 1 Hz – 14 kHz
  • Resolution lines: 1,638,400
  • Simultaneous input channels: 4
  • Balancing capability: Yes
  • Compatibility with mobile devices: Yes
  • Noise: Ultra Low

Learn More ->

Permanent Vibration Analysis Equipment

Permanent Vibration Analyzer – Phantom®

Phantom is a Permanent Vibration Analyzer with Wireless connectivity and Ultra Long Battery Life. This is a set of sensor designed for permanent mounting. Phantom records vibration FFT from 3 axes simultaneously X, Y and Z. In addition, it includes a battery with duration of 2 to 5 years that can be changed at the end of its useful life.

  • Frequency range: 1 Hz – 10 kHz
  • Amplitude range: 32g
  • Resolution lines: 6,400
  • Simultaneous channels of entry: 3
  • Compatibility with mobile devices: Yes
  • Noise: Low

Learn More ->

 

2. Verify the number of input channels

You can find vibration analyzers in the market with different number of input channels, the most common being 2 to 4 channels.

Recording 2 channels simultaneously is usually enough for functions like balancing, phase analysis, Bode graph and ODS (these functions will be explained in another article). On the contrary, the use of a triaxial accelerometers as well as o 2 simultaneous planes balancing require 4 channels.

Single channel analyzers are not common anymore since they are unable to perform necessary techniques necessary for some of the most important faults, like misalignment, Bode and balancing.

 

3. Understand Lines of resolution and Resolution

The number of lines of resolution defines how many points will integrate the spectrum. Although the correct term should be “Points”, the word “Lines” is still used probably because it was created  for in audio FFT  which were plotted with bars (or lines).

 

The lines of resolution are sometimes wrongly associated with the resolution of a spectrum; however, this is not entirely correct. The LR do not distinguish between a large or short frequency range, thus, having a lower frequency range will show a better resolution a higher range with the same amount of lines. Observe the following example:

Example 1

Suppose we select 6400 LR, let’s see these 2 examples:

Max Frequency of 10,000 Hz: 10,000 / 6,400 = 1.56 Hz (93 CPM) smile

Max Frequency of 1,000 Hz: 1,000 / 6,400 = 0.156 Hz (9.3 CPM) sad

The second example will show 10 times the resolution of the first one.

 

In other words, you will look for precision in a spectrum when you need to differentiate between two frequencies that are close to each other.

Example 2

Imagine a fan with pulley transmission in which the pulleys have very similar diameters and thus work at few RPMs between each other.

machinery database

machinery database

To distinguish the imbalance of the motor from the fan, you will need enough resolution to get the two frequencies to show in independent peaks in the FFT and therefore measure the amplitude of each one. In case your maximum resolution lines were of 6,400 you would have to sacrifice your maximum frequency having to set a range of 200 to 400 Hz and thus not seeing the full range of the accelerometer.

In conclusion, the lines of resolution are a very important factor in the choice of the best Vibration Analyzer since your resolution and frequency range are extremely related to it. Hence, the analyzers capable of calculating millions of lines of resolution will rarely have to sacrifice frequency range to achieve excellent resolution.

 

4. Frequency Range in the best Vibration Analyzer

The frequency range of a vibration analyzer is determined by two factors: the highest sample rate of the analyzer and the maximum frequency that the accelerometer can measure. The Sample Rate is the amount of measurements that a system can perform within 1 second. Thus, the maximum frequency that this device can see will be half of its sampling rate.

As an example, a system that samples at 20 kHz will have a maximum frequency of 10 kHz[i]. Think of it this way, if we had a signal of 1 Hz (1 cycle per second), to be able to see its wave form, that is to say in its negative part and in the positive part we would have to make a measurement at least 2 times per cycle.

Accelerometers, on the other hand, have a maximum and minimum frequency (usually 1 Hz to 10 kHz) that they can measure accurately. Outside of these limits, the sensitivity can be progressively different, so it is not recommended to make measurements outside their range.

Generally speaking, the frequency range of an analyzer is usually higher than the frequency range of conventional accelerometers, but having a wide range will give us the freedom to connect sensors with higher ranges.

[i]In fact for this calculation we should be using Nyquist frequency which we will see in another article. But this means that the real divisor is 2.56 instead of 2.

 

5. Check for Additional functions

Are you still here? Excellent now pamper yourself a little and go grab some cookies or gummy bears, because it gets better.

Finally! we got to the part that I like the most. The functions of the analyzers are probably the part that changes the most between one analyzer and another. I will start by listing the most important functions that every analyzer has, or at least should have and these are:

FFT

Spectrum, is the heart of an analyzer, almost all analysis functions need it inside their calculation. Not to mention FFT measurement tools and Window functions: Rectangular, Hann, Hamming, FlatTop.

FFT

FFT

Check out a FFT definition here:

Time Wave Form

Vibration analyzers draw this chart with the signal as it arrives from the sensor. It is not used very often, however some secondary functions like Circular Time Wave Form are useful to detect patterns in gearboxes or bearings.

Time Waveform

Time Waveform

 

Measurement parameters

Acceleration, Velocity, Displacement and Acceleration Envelope (Demodulation or equivalent, useful for early bearing fault detection)

Vibration Data Collector

A good vibration analyzer should also be a vibration data collector. At least it should have a mechanism to store and organize the recordings of the machines to store a history and trend of the machinery. This is one of the main factors to consider because consider that you will be dealing with this part of the system EVERY day. Having an intuitive and easy-to-use database interface is vital to avoid wasting time later.

Machinery database

will store all the information related to your machines and all your recordings over time.

Envelope alarms

The theory tells us the ideal vibration levels for some of the machinery in the industry, but what will you do if you do not know what the ideal value is? This tool will let you know the moment the vibration increases in any of its frequencies. It wraps the full spectrum and rings an alarm whenever any frequency grows more than the percentage you configured.

Envelope alarms for vibration analysis

Envelope alarms

Reporting tools

Reports can be very tedious if you create signal by signal, value by value. Automatic reporting saves considerable time.

Dynamic Balancing 

Dynamic balancing is a functionality which is present in the vast majority of equipment usually as optional, however, consider that imbalance is one of the most common causes of vibration in the machinery, wouldn´t it be nice to correct the problem instantly?

Polar graph for balancing

Application for balancing

Phase analysis

Phase analysis requires you to record at least 2 channels simultaneously in order identify the direction of motion compared to each other. This function is mandatory to fully diagnose misalignment among some other faults.

Bearing database

This function is is important because bearing vibration analysis identifies fault frequencies related to bearing geometry. Thus, you a complete bearings database to obtain the manufacturer information to perform faults calculations.

 

6. Advanced functions in Vibration Analyzers

The advanced functions may or may not be present on many systems, or could have different names than those I will mention.

ODS

(Operating deflection shapes) Simulates the movement of the whole machine in a 3D drawing. This is a tool that is not so common but is excellent for diagnosis and above all, it is very easy to understand for anyone, even people with little or no knowledge of vibration analysis. ODS is also undoubtedly a very attractive tool that sells for being so descriptive.

The best vibration analyzer - ODS 3D Simulation

The best vibration analyzer – ODS in Vibration Analysis

Bode Chart

More than just a chart, it is a function to diagnose resonance and critical speeds during machine coast down.

The best vibration analyzer - Bode Diagram

Bode Diagram

Orbits

It is a two-channel analysis in which 2 sensors are placed at 90º, orbits help to understand the behavior of the shaft within the bearing, as well as the modes of vibration and resonances if it is done within a run down test.

Circular TWF

(Circular Time Wave Form) or circular waveform. This function is useful for vibration patterns interpretation in very low speed systems, like gearboxes. It is essentially the time domain graph plotted in a circular chart in which you can select the time to complete 360º thus, superimposing several cycles. Patterns can be easily seen when peaks overlap in the same position.

The best vibration analyzer - Circular Time Waveform

Circular Time Waveform

Cascade

It is a 3D representation of the spectrum over time, very useful to detect resonance and natural frequencies.

The best vibration analyzer - Cascade plot

Cascade plot

FRF

(Frequency Response Function) or transfer function. This function helps measuring transferred vibration from a source in all its frequencies. For example, we know that a spring absorbs lower frequencies better, and rubber absorbs higher frequencies better thanks to this function.

Coherence Function

Is meant to verify the origin of a vibration. Imagine a room with several machines, and a vibration outside of this room but generated inside of it. In order to determine which of the machines is responsible for this vibration you will need this function to gain certainty.

 

6. Cloud connectivity when choosing the best vibration analyzer

Some new vibration analyzers offer already a cloud based database to be shared with your customers. Sharing you vibration database with your customers, not only will it make your life easier reducing the amount of reports, but also it will give your customers the satisfaction of having the best technology available.

Look at an example here: EI Analytic Vibration Cloud

7. Verify which Sensor types can be plugged into your vibration analyzer

Accelerometer

The output voltage is proportional to the acceleration of the vibration. Most of these sensors require power supply because they contain small amplifiers and filters to eliminate noise.

Accelerometers for Vibration Analyzer

Accelerometers for Vibration Analyzer

Vibration Analyzers most commonly use Accelerometers due to their excellent frequency and amplitude range as well as the low noise they generate. In return, they convert acceleration into other parameters like velocity and displacements which are more frequently used in vibration analysis.

Velocimeter

Its signal is proportional to the velocity of the vibration. They are electromagnetic sensors, so they do not require power.

Displacement probes

The output signal is proportional to the displacement of the vibration. They usually are non-contact sensors, so they are ideal for measuring vibrations and eccentricity of shafts.

 

It is convenient that the vibration analyzer you choose has the possibility to connect other types of sensors. There are machines for which simply the accelerometer is not the appropriate tool. Oil bearings is an example of the above because oil dampens the vibrations thus making its measurement with accelerometers less reliable.

 

8. Take Portability in account, but do not sacrifice power.

Take in account the portability of an analyzer since you will be dealing with this every day. On the other hand, you must also consider that a small device with little functionality will be a big limitation.

In terms of portability, the general types of analyzers are the following:

Pen type

People use these usually only to measure vibration RMS, the functionality is usually very pour, although they have the great advantage that they fit everywhere, even in your pocket.

Hand-held

They are devices the size of a cell phone, have a larger screen, show the spectra and are well prepared for taking routes. They are very portable and comfortable for use. These vibration analyzers usually have slow processors, so the number of lines of resolution, memory and functions are reduced, thus requiring PC based software to complement functionality.

Propriety Tough Devices

They range from the size of a cell phone to beyond the size of a tablet but with a greater thickness. They are the most common and are a fair choice for industrial use. There are many brands and with very variable functionality.

The disadvantage is that they are not universally used devices and, thus, the cost of manufacturing them is high. This makes them have slow processors and low memory. This condition can make these systems less functional.

It is complicated to know what kind of processors these devices have because it rarely appears in the technical file. Our best approach will be to evaluate trough the amount of memory and functions of which they presume. The good news is that most of these computers have PC software to make analysis of the data collected easier. We just need to be aware of the cost of this software.

Tablets and PC

They are becoming more popular due to the huge power and memory of new computers. Updating the computer generates no cost while installing the software and also portability in comercial tablets increases on every new model.

A small disadvantage is that most of them are not sweated for industrial environments, however, Windows and Android rugged tablets are available at very affordable prices without the need to by tied to a brand.

digivibe-vibration-analyzer

vibration analyzer

9.  Never underestimate Technical Support

In the best vibration analyzer, support is a very important aspect because, let’s face it. Nothing is ever perfect and we always need a assistance for complex devices. Thus, you will need to be in contact with the distributor or the manufacturer of the product with certain frequency. The most important points to take into account for technical support are:

  • Cost: Is there an additional cost for support?
  • Speed to answer our questions.
  • Shipping time for spare parts. If you do not have backup system, you will have the equipment broken for more than a month which will surely cause delay in your production or services.
  • Possibility of speaking by telephone with the technical team.

 

10. Verify the Price for your Vibration Analyzer

Last but not least, price is one of the main factors to take in account. Understand how you will be charged, this  is vital to calculate our financial capacity for acquisition. Points to take in account:

  • Price: Identify the price of the system as well as needed accessories, software and other possible features.
  • Annuity: In some cases, you need to consider an annual license fee for support. Check before you buy.
  • Cost of spare parts: Do not forget that at some point you will have to change a cable, a sensor, or the complete module, so I recommend you to be sure it is within your possibilities.
  • Update cost: Most brands update their equipment regularly, check the costs of these updates.

 

Bonus – Now please Read about our Digivibe Vibration Analyzer here.

 

Related Articles:

 

Análisis de Vibraciones

A B O U T  T H E  A U T O R

Thierry Erbessd, Mexican entrepreneur who has revolutionized the field of Vibration Analysis and Dynamic Balancing worldwide.

Thierry is a graduate of the National Polytechnic Institute of Mexico and is also a passionate programmer, he is the creator of DigivibeMX software that competes among the best systems for vibration analysis. He is currently the President of the Erbessd Instruments group, a leading company in solutions for industrial maintenance.

ERBESSD INSTRUMENTS manufacturer of Vibration Analysis Equipment and Dynamic Balancing Machines with offices in Mexico and the United States with representatives around the world.

Wireless Accelerometer Vibration Analyzer

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Condition Monitoring - Wireless Accelerometer Condition Monitoring - Vibration Analyzer Condition Monitoring system

 

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