Centrifuge Controls

[RB99]

Hi all,

I understand almost nothing of what you guys talk about here. I joined because I am currently designing centrifuge control systems and figured people using them day to day might offer some insight and opinion.

At the moment I am particularly interested in w2t (or w2td) control.

Firstly does w2t mean much to anyone here? You know, 400 million w2ts means something to someone?

My understanding is w2t is the integral over the run time of rotor speed (rads/s) squared. Because you can measure rotor speed more accurately than you can control it w2t control has the advantage of allowing automatic adjustment of the run time to compensate for rotor speed variation.

This is a real advantage providing more repeatable results and is something I would like to include in the control system.

w2t with units of (I think) rad^2/s and huge numbers (like say 4.4 billion w2t for 30 minutes at 15,000 rpm) doesn't seem to be very user friendly but if users understand it I should go with it.

I am also considering 'rcft' with units of gs, g * seconds seems to easier to understand and won't have such huge numbers.

Your thoughts and opinions would be welcome, as would pointers to anywhere else centrifuge users hang out.

[L106]

If the computer monitor was a TV screen, you would probably be seeing a lot of blank faces. (Sorry!)

[RR1]

Hi RB99, for most of us a centrifuge is merely a tool to get from a sample of whole blood to a separated sample. It has a time and a spin speed ...that's it. You need to tell us in plain English what you are trying to achieve, so we can help.

Other centrifuge users?......you could try NASA, I think they do gs there with their astronauts????

[Lcsmrz]

Using w2t would be great process control in component preparation, rather than setting time and RPM. But few of us understand how it would help us make better, more consistent products.

There would be a certain learning curve yu'd have to get over to make it a marketing enhancement.

[RB100]

RB99 here, lost the login I used originally. I didn't bother checking for responses after the 1st month, and about 2 years later the thread with some responses turned up in a google search for me.

Thanks for your comments. The centrifuge control has been done for a while now with w2t. Ended up calling it RCFt with units of km/s. Effectively the velocity the sample would have at the end of the run had it experienced the same g force in a straight line (ignoring the laws of physics because the speed of light is easily exceeded).

You still need to set rotor speed. You can stop the run after a set time or optionally after the sample has reached this notional velocity. It is a little more accurate and repeatable because it is based on accurately measured rotor speed. RCFt is displayed either way, if you set a time the time counts down to zero and RCFt up from zero, if you set an RCFt time counts up and RCFt down.

Edited January 7, 2011 by RB100