[RASMB] Time-stamp checks for SV data

[Walter Stafford]

If the acceleration is linear - which I think it is on the XL-A/I - you use 1/3 the acceleration time as the time offset using w^2 at full speed.

Walter

_________________________
Walter Stafford
wstafford3 at walterstafford.com



On Jan 25, 2013, at 13:40, Borries Demeler wrote:

> Hi Glen,
> 
> As Walt pointed out, we all need accurate w^2t integral values for
> accurate analyses. In an effort to guard against the problem Rodolfo
> reported we routinely check the time elapsed in UltraScan to see if we
> get *reasonable* values, you can make a plot of t vs. w^2t integral for
> each scan and see if you get a reasonable intercept. So, UltraScan users
> with ProteomeLab 6, please check the time correction value in the run
> details window. However, this approach only works of course if the w^2t
> value is correct, and that cannot be checked with a time server. If you
> are relying on time from filestamps you run the risk of messing things up
> if you copy files and they end up getting assigned new filestamps :-)
> 
> A related issue is perhaps how accurate the acceleration setting is.
> If you set the acceleration to 400 rpm/sec and accelerate to 60 krpm,
> you should reach 60 krpm after 2.5 minutes. Our instrument pretty
> much is right on, and that gives you the ability to calculate the w^2t
> independently to make sure you get the right w^2t at a given time (our
> machine gives the right values). Perhaps someone with Proteomelab 6
> could try that? A stopwatch is all you need for this.
> 
> Thanks, -Borries
> 
> 
> In-Reply-To: <883495.48409.bm at smtp101.vzn.mail.bf1.yahoo.com>
>> 
>> On Fri, Jan 25, 2013 at 01:14:00PM -0500, Glen Ramsay wrote:
>> Greetings All:
>> 
>> An underlying assumption is that the computer clock is accurate.  Usually
>> this is the case, and when it fails, it is because the mother board watch
>> battery has died while the computer was turned off (not an experiment
>> problem).  Computers connected to the network check their time via a time
>> server, but this function only sets the time, it doesn't log time errors.
>> Hopefully any small time changes aren't going to be a factor.
>> 
>> NIST has time servers that can be polled.  In principle the data
>> collection software could validate the elapsed time by this means.
>> 
>> Is the current situation adequate, or do we need to use the time servers?
>> My feeling is we don't need the time servers, but I'll throw out the
>> idea for discussion.
>> 
>> Glen
>> Aviv  Biomedical, Inc.
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> 
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