From: Don K Mc Rorie <dkmcrorie@ccgate.dp.beckman.com>
  To  : rasmb@bbri.eri.harvard.edu
  Date: Wed, 28 Jun 1995 15:26:53 -0800 (pst)

w^2*t

In response to all the questions about how the time and w2t on the XLA 
are calculated, I spoke with Barney Hedges in engineering and here are 
the eaasiest explanations:

1. Time on any run begins when the rotor starts spinning. It is only 
reset when the rotor stops spinning so any changes in rotor speed do 
not affect the time being recorded.

2. w^2*t is calculated according to the following formula within the 
software of the centrifuge:

w^2*t = w^2*t + (constant * speed * speed * deltatime)

where:
a) constant is the conversion factor from rpm squared to angular 
velocity
b) speed is the current rotor speed in rpm
c) deltatime is the elapsed time sime this function was last 
calculated

This function is calculated approximately every 100ms. In this way, 
w^2*t is the value expected for the time integral of angular velocity 
squared and as with time would include all events of multiple speeds 
used in a single run. w2t is cumulative from the start of the rotor 
spinning and does not reset until the rotor stops.

3. The time format (HOLD, time, w2t) stipulated by the user has no 
effect on the values recorded on the scans.


I hope this clears some of the misunderstandings

Don