Any tutorials for analysis, acquisition, PROTOR etc

What engineering decisions are made by measuring a power spectrum?

By power spectrum we are talking about an ASD (Auto Spectral Density) or PSD (Power Spectral Density). In fact PSD is often used when really ASD would be more correct.

Taking any signal and performing a frequency analysis using an ASD or a PSD will give the energy over a range of frequencies. (more…)

There is no simple answer, simple terms like load and spectrum can be used in different situations and therefore to mean different things. However the most common definition of load spectrum is as follows… (more…)

How Do I Convert To Decibels?

Much confusion revolves around linear and non-linear numbers. The following outlines the mathematical process to convert from a number expressed in dB to a linear quantity. How do we convert to decibels and back again? (more…)

What is Auto Spectral Density?

The Auto Spectral Density or Auto RMS spectrum analyses uses Fourier Transforms to process optionally overlapped sections of the input data. The result of each Fourier analysed section is called a periodogram. We then process all the resulting periodograms to produce a spectral result. (more…)

[Video] Exporting DATS datasets in non-linear format

To complement our recent post on Exporting DATS datasets in non-linear format here is James Wren demonstrating the method. https://www.youtube.com/watch?v=sh6Q3FwjtR4

Exporting DATS datasets in non-linear format

The following tutorial shows in detail how to use Prosig DATS to export data in a non-linear format.

DATS stores all data in linear format. When you export data you are exporting the raw stored data. Therefore, to export data in a non-linear fashion we must convert the data to non-linear scale (dB for our example) and then export to the desired format, in this case CSV. (more…)

What Sample Rate Do I Use To Measure Whole Body Vibration?

What sample rate should I use if I am measuring whole body vibration? Strict ISO8041 compliance imposes a minimum sample rate of 900 samples per second. This ensures the amplitude…

What Type of Accelerometer Should I Use? IEPE, Charge or Bridge-based?

What type of accelerometer should I use? What are the advantages/disadvantages of a charge mode accelerometer, an IEPE accelerometer and a bridge based accelerometer?

There are so many types of accelerometer that is often difficult to know what type of accelerometer to use. An IEPE accelerometer will have a high pass filter at about 5Hz. The charge type will, by it’s nature have what is effectively a high pass filter at about 0.1Hz. Therefore neither type will show DC levels. The charge type will usually have a lower frequency bandwidth than the IEPE type. Charge accelerometers can be used at higher temperatures however. (more…)

How to set up scheduled data captures

A video that explains how to set up the DATS Data Acquisition software to perform captures at specific, scheduled times. https://www.youtube.com/watch?v=jeJ6a0U9vjk

[Video] Create AVI files from your structural animations

The DATS Modal Analysis software consists of Hammer Impact Testing, Modal Analysis & Structural Animation (often referred to as Operational Deflection Shapes or ODS and Running Modes). Having measured and…

Relative signal levels of a sinusoid with and without background noise

In the process of looking at some order data, a question about the accuracy of the measurement of the signal level of discrete frequency signals which were close to the general noise level.  To answer this question, a small DATS worksheet was created which generated 2 signals.  The first signal was a 35 Hz sinusoid which, by itself the spectrum level was measured to be approximately -9 dB (ref 1 V) as seen in Figure 1.

Creating calculated signals with DATS Acquisition

Case Study: What can I do if the transducer I am using has a non-linear sensitivity over its measuring range?

Abstract

Recently a PROSIG user wanted to measure a specific temperature parameter on a running engine. The transducer being used was one of the engine sensors built into the engine operating system to minimize engine emissions and maximize fuel economy. Unfortunately, the sensitivity of this transducer was not constant over the desired temperature range. The question then became, how can the output from this non-linear transducer be used to accurately measure the desired temperature parameter? (more…)

[Video] Creating speed signals for data with no tacho

So you've got some noise and/or vibration data from a rotating machine, but no speed information. Surely that means you can't analyse against speed or do any order analysis, right?…

[Video] Using reference cursors to measure data

A tutorial by James Wren (Prosig UK) on how to use the reference cursors in the DATS software to precisely measure features in your data. http://www.youtube.com/watch?v=PSnldTfaQIE

How do I find the natural frequency of an inlet manifold?

There are a number of ways to find the natural frequency (resonance) of a part like an automotive inlet manifold. Here are three different types of popular test techniques. But which one should you use and why?

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How do I perform vibration analysis on a cylinder head and inlet manifold?

We were asked the following question…

I want to perform some cylinder head and inlet manifold vibration analysis, what should I do?

First we need to consider sensor selection (more…)

[Video] Storing FRFs, coherence & time series

James Wren (Prosig UK) explains how to store FRFs, coherence and/or time series data in modal hammer testing using Prosig's P8000 & DATS software. http://www.youtube.com/watch?v=JLumlmoRCvM

[Video] What are nodes, components & structures in modal testing

James Wren (Prosig UK) explains how nodes, components & structures are used in modal hammer testing using Prosig's P8000 & DATS software. http://www.youtube.com/watch?v=FmNCqv7p3pc

Calibrating an Accelerometer with a Prosig P5000 system

Here we look at how to calibrate an accelerometer using a Prosig P5000 system. Put the wax on the shaker top. Place the accelerometer in the axis you wish to…

[Video] Disabling P8000 cooling fans during data capture

Justin Foster (Prosig UK) explains how to set up the DATS software to switch off the P8000's cooling fans during data capture. This can be important to reduce noise during…

[Video] Performing a Hammer Impact Test

James Wren (Prosig UK) provides a step-by-step guide to performing a Hammer Impact Test on a structure using Prosig's DATS software and P8000 data acquisition hardware. http://www.youtube.com/watch?v=YrCM3H0_NpE

[Video] Calibrating a strain gauge for use with a Prosig P8000 system

James Wren (Prosig UK) steps through how to calibrate a strain gauge for use with a Prosig P8000 system. http://www.youtube.com/watch?v=BAh9PS632Tk

Reference frequency for third octave filters

We are using the third octave band filter at very low frequencies (~1Hz)  and I noticed that the response of the filter could introduce very significant errors for short or transient signals. Looking a bit more in details at the function, the help says:

“For audio work ISO standards use a reference frequency of 1kHz not 1Hz”

Does that implies that for non-audio work, a reference frequency of 1Hz should be applied? If yes, is it possible to change this reference frequency in the dats function?

Dr Mercer replied…

Essentially there is no problem and no need to change the reference frequency provided you use Base 10 mode and not Base 2. Base 10 is the ANSI S1.11-2004 preferred scheme. (more…)

[Video] A simple CAN-bus measurement setup

A simple tutorial that explains how to use the DATS Acquisition software to set up a Prosig P8000 to capture data from a CAN-bus. http://www.youtube.com/watch?v=XeAuntGW-O4

How do I balance a shaft?

“How do I balance a shaft?” seems like a fairly straightforward question, but there are a number of things that we need to understand first. Here we look at a number of key concepts that need to be understood in order perform balancing.

What does balance mean?

Well broadly speaking to balance a shaft, mass must be added or removed at certain angles. The concept being that the centre of gravity and rotational centre of the shaft will be equal when the shaft is balanced. (more…)