How to define other sensor types

[c-dot]

Hi everybody,

I'm trying to measure some transfer functions. The exciting signal is a dynamic force (ICP sensor) and the responding sigbnal is a velocity (no ICP). Where do I find this sensor type in the DAQmx Assistant or rather in Sound and Vibration Assistant.

Do I have to define those sensor types?

Further on, I want to calculate the spectrum of each channel/sensor and the transfer function as well as the coherence of these signals.

Thanks in advance

[Jochen]

c-dot,

do you mean, you generate a dynamic force and measure it with an ICP sensor (how?) or do you measure the acceleration of a moving part, that applies the force, with an ICP sensor? What type of velocity sensor are you using and what are the specs of this signal? Is this a voltage that is proportional to velocity?

Anyway. If you can't find the exact sensor type that you are using in MAX, you always can do a voltage measurement and add an NI-DAQmx scaling (also available in MAX).

I hope that helps,

Jochen Klier

National Instruments

[c-dot]

Hello Jochen,

I use a shaker to excite my test object. The exciting force is measured by an ICP-force sensor:

http://www.pcb.com/spec_sheet.asp?model=288D01&item_id=11049

and the surface velocity of the test object is measured by a Laser-Vibrometer

http://www.polytec.com/ger/158_839.asp

I have already tried to do a voltage measurement, but there is no ICP-supply available. Thus, I think the measurement will not be correct and I cannot define physical units.

So, there is no other way to define another sensor as the ones already implemented?

Thanks

c-dot

[Jochen]

For the ICP sensor it should be possible to use the acceleration sensor template in MAX. Still as the output is not directly proportional to velocity, you will have to integrate the results. Which data acquisition hardware are you using for this type of sensor?

As much as I can read from the Polytec datasheet, the vibrometer outputs a voltage that is proportional to velocity, so scaling should be an easy solution for you.

Jochen

P. S.: Which type of development software are you using? According to your name this could be .NET :-).

[c-dot]

Hello Jochen,

I try to implement your advices.

Is there a possibility to change the physical units of the signal: g or mm/s² to N?

What do you mean with developement software? (Sorry, I'm a bloody newbie) I do not actively use .Net, although my name seems so ;-). I will tell you tomorrow about my results.

Thanks

c-dot (Christian)

[Jochen]

Hi c-dot,

again scaling is the answer to your question. You can use scaling also to convert the physical unit of your signal.

With development software I meant your programming environment (LabVIEW, C, C#, Delphi,...).

Regards,

Jochen

[c-dot]

Hello Jochen,

you are right. Scaling works for the laser-vibrometer. The force can be measured as acceleration. Next step is to change the unit of the measured signal.

I am not realy sure which environment I should use. Because I have an academic license, I can work with SignalExpress, Sound&Vibration Assistant and LabView. I kind of "like" working with LabView, because it can calculate transfer functions, coherence and so on.

Greetings

C-dot

[Jochen]

C-dot,

if the functionality that is provided by Sound&Vibration Assistant meets your requirements, it's worth trying it, because it doesn't require programming. On the other hand if you are looking for a more flexible solution, LabVIEW is the better choice.

Jochen