Dear Amlaan,

the main advantage of the LV is to be contactless, meaning preventing any alteration of the structural vibration to be measured due to the weight of an accelerometer and attached cable, the cable tribo-electric noise etc. The only element you have to implement on your test object is a bit of reflexive tape.

It provides in particular a very effective way to measure rotor vibrations (not requiring to embark a sensor, re-balance the rotor and use a rotating contact or a transmitter to deliver the vibration sensor signal); or to measure the vibration of thin plates or very lightweight structures.

Another benefit is to allow scanning the vibration in a large number of positions if you add a motorized mirror - assuming of course the stationarity of the vibration field.

Conversely it requires a very stable fixture and a controlled environment - it is not an easy instrument for field tests in industrial environments...

You need also to have in mind that you will measure only the vibration component along the laser beam

Last but not least, as it measures the vibration velocity and not directly the acceleration, it is not suitable for high frequencies (the sensitivity decreases by 2*pi*frequency compared to an accelerometer)

You will probably find more on web encyclopedia or manufacturer's docs

Hope this helps!

Dear Almaan,

You can find a review of Laser Doppler Vibrometry and an example of application in Vibration Control for Optomechanical Systems, World Scientific, 2022, Chapter 4. https://doi.org/10.1142/12290; https://www.amazon.com/Vibration-Control-Optomechanical-Systems-Vyacheslav/dp/9811237336/

Hello Almaan

Ther is one additional but very important point to add to the answers you got already:

The Laser vibe measurement is a relative vibration between the Laser fixture and the structure you aim at, whrereas an accelerometer measures the absolute (in space) vibration. This must be considered to interpret the results correctly and leads by the way often to measuring difficulties because of low frequeny or static displacement between the Laser support and the target.

More about that you may find on my website:

https://www.f3lix-tutorial.com/frequency-related-properties

Felix Schmid In that respect do you mean to say that accelerometers are better due to the fact that one gets the absolute value

Accelerometer data readings can also be dampened depending on a machine or something else which might be moving in the background thats also a disadvantage . In this a laser vibrometer has a clear advantage as per my understanding

Amlaan

Absolute is not any better or worse than relative. Relative means here that Laser measurement is based on velocity or distance between the laser equipement and the target you shine the lasaer on. that measn it is a relative velocity or or displacement between the two points in space. This implies also that if the support of the laser is somehow moving (vibrating) yourmeasurment includes also this movement.

With an accelerometer on the target you measure absoute acceleration (or if integrated absolute velocity or double integrated absolute displacement) Absolute means that the measurement is "with respect to the space" i.e. absolute velocity and not relative to some other object.

I don't understand what you mean by "Accelerometer data readings can also be dampened depending on a machine or something else which might be moving in the background" The accelerometer will always measure the complete absolute acceleration at the place it is installed (of cours within the frequency limits of the accelerometer)

Hello Felix

I will reformulate my sentence.

I meant knowing the fact that an accelerometer is contact based it might take into account vibrations that are running in the background which might lead to a bad result in the end is this different in the case of laser vibrometer ?

Sorry Amiaan, Physics dictate that any sensor will measure the local level of vibration whatever the origin, so environment-induced vibration will equally be recorded by the LV. And you have to be further cautious to protect the LV device and mirrors from this environment-induced vibration...

As previously commented, if you use an accelerometer, its mass will also alter the vibration reading, which is not the case of LV - this is the main difference!