Free falling hammer

[johnsold]

Przemek,

You seem to use slightly different mumbers in each post. Please tell us exactly what you need to measure and when.

Do you need to know the position of the hammer from just before it hits the specimen until it stops moving? Does the hammer rebound after fully copmressing the sample? At how many points in that range do you need to make position measurements?  Every mm? 0.05 mm? 0.01 mm? Accuracy and resolution are not the same thing. You could have very good accuracy with poor resolution, the opposite, or have both be very good.  Cost varies accordingly. I presume you need to synchronize the force measurements with the position measurements, correct? How are you measuring the force?

To make useful suggestions we need this detailed information.

Lynn

[przemmo]

Lynn,

In the first post I specified, that I need accuracy of 0.01 mm. The position (s) measurement will be used to plot the relation force- position F(s).

It takes about 0.01s to stop the hammer after it hits the specimen. So average deceleration is 1000 m/s^2. The specimen is a energy absorbing element so it folds. This means that at the beginning the force is higher till the metal folds (attachement).

I need to measure its position from the moment just before it hits to the moment it stops. It rebounds, but no more than 5mm. The measurements must be taken every 0.01 mm with the same accuracy, what in practice means higher measurement resolution.

To measure the force I use 3 PCB impact sensors (piezo).

Przemek

[unclebump]

This device can measure 230,000 fps.

http://www.keyence.com/products/microscope/microscope/vw9000/vw9000.php

[przemmo]

Thank you, but camera based system is no longer a good solution.

I found an encoder resistant to 3 000 m/s^2 shock. Do not know whether this shock can occur during operation, how the shock affects its operation.

http://www.baumer.com/fileadmin/Downloads/Catalogs/Sensor%20Solutions/pdf/2046_en_802364_MAGRES_herm...

I need a sensor that can work under 3 000m/s^2 acceleration.

[EmcV]

From my point of view it is just another impact tester..

First hit on goolge:

http://www.wpi.edu/academics/Depts/CEE/Research/structure.html

I think high speed camera is far mor expensive than simple LVDT mm.  Rather simple to aquire and resolution can't be a problem.

It's more difficult to get that range vs resolution with a camera. However, a movie like that sells itself.

[przemmo]

no no, the parameters of your system are a few times below my system's. I know Google, its really powerfull machine, but I have'n found so far.

LVDT are not able to measure displacement with that speed and that resolution and accuracy- excitiation frequency. (?). 

Your example documents a 100 g impact system.

Przemek

[EmcV]

Ok. As alternative the High speed laser is well known but with an eddy current sensor (eg liionprecision or microepsilon) you can optain very high resolution and frequency response.