Measuring position of spring mass

[Nester]

I have a spring-mass system set up, and I'm trying to plot its position over time. I bought a Ping))) ultrasound sensor, and I have it wired to my Arduino so that it detects the position of the bottom of the mass. My idea was to pull the mass down, then release it and have the sensor capture the oscillations over time. However, the problem I'm finding is that the mass doesn't just oscillate neatly up and down: it bounces around in all directions, so it's hard to get a consistent reading without a lot of "noise".

 

Does anyone have any ideas for an apparatus I can use to make sure the mass oscillates vertically, without affecting its natural frequency (i.e. not slowing it down)? I'm thinking along the lines of a hollow cylinder that I can snap around my stand, with a bar to attach to the mass, so that the mass moves up and down in time with the cylinder. I'm not sure if that's available, or if I'd have to build it (and if I do, then how to keep the friction between the cylinder and the stand as low as possible).

 

Thanks,

 

Nester

[timo]

Depending on what you want to measure these ideas may or may not help/work:

1) Improve how the upper end of the spring is fixed. If if is just hanging from some rod glueing it to the rod may help

2) Reduce the forces involved by using smaller deviations from the equilibrium

3) Use a softer spring to achieve smaller forces with larger deviations

4) Maybe a small string between spring and mass can eliminate the spring's torsion to transfer to the mass. This may create new problems, tough

 

I remember having done a double-spring system as an undergrad. It was a lot of trial and error to get the system stable but we eventually a working combination of springs and masses that allowed data analysis. So a single-spring system should be feasible without too many headaches.

[foxy john]

A soft spring and a heavy weight.

I think it would be best to try and scale up as far as practical. Maybe use a lot of elastic bands to get something a couple of meters long, then put a 100g weight on the end. That should move a reasonable distance at speeds you can measure. Either measure it optically or with a coil.

[Robittybob1]

I have a spring-mass system set up, and I'm trying to plot its position over time. I bought a Ping))) ultrasound sensor, and I have it wired to my Arduino so that it detects the position of the bottom of the mass. My idea was to pull the mass down, then release it and have the sensor capture the oscillations over time. However, the problem I'm finding is that the mass doesn't just oscillate neatly up and down: it bounces around in all directions, so it's hard to get a consistent reading without a lot of "noise".

 

Does anyone have any ideas for an apparatus I can use to make sure the mass oscillates vertically, without affecting its natural frequency (i.e. not slowing it down)? I'm thinking along the lines of a hollow cylinder that I can snap around my stand, with a bar to attach to the mass, so that the mass moves up and down in time with the cylinder. I'm not sure if that's available, or if I'd have to build it (and if I do, then how to keep the friction between the cylinder and the stand as low as possible).

 

Thanks,

 

Nester

Have you tried hanging it upside down? Is the current set up with the mass below the spring?

Edited April 2, 2016 by Robittybob1

[Sensei]

I would use fast recording camera for this type of experiment.

Plentiful even relatively low cost cameras can record 120 FPS, with limited quantity of frames.

But 1000+ FPS would be great. Depending on your funds.

Behind it place something with precisely draw vertical and horizontal lines, or checkerboard, allowing easier estimate distance.

 

Alternative method is sending photons by laser and measuring time needed them to return to receiver.

The longer distance the larger delay between emitting them and receiving back.