<div>Thanks Walter. The difussion pump was on. I did try longer equilibration time (>3.5hours). It helped stabilize the vacuum. But I still suspect that the pump is having the problem. The temperature shift may be OK.</div>
<div> </div>
<div>Chin<br><br> </div>
<div><span class="gmail_quote">On 10/20/08, <b class="gmail_sendername">Walter Stafford</b> <<a href="mailto:stafford@bbri.org">stafford@bbri.org</a>> wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Hi Chin,<br><br> This could be caused by the switch from the thermistor to IR temp. sensing mechanism. The switch occurs at 100 microns of pressure in the chamber. You can avoid this usually by turning on the diffusion pump while you are equlibrating the machine before the run. And to accomplish that you must enter a speed of 0 (zero) and press "Start". If your rough pump is not pulling the vacuum below 100 microns, the switch to the IR sensor will not occur before you start and the diff pump heats up. I have seen this on both my machines. It also sounds like your vacuum gauge calibration may be off. I am surprised that this lead to so much extra noise, tho.<br>
<br>Walter<br><br>QCZ wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<div><span class="e" id="q_11d1bb5c305bece7_1">Hi all,<br>I have recently seen a vacuum jump from 9 microns to 45 microns during the acceleration to 50K rpm. At the same time, the temperature goes up to 20.4C from the set temp of 20.0C. It came back stepwise to 20C after 2 minutes based on the temperature plot in sedfit. My experience is that this cooling took too long. The data fit was really noisy with the rmsd of 0.015 (total OD280=0.9) or above and the residual was bad for the first 45 scans. Is this a vacuum issue or the temperature control problem? Any input will be appreciated. Thanks.<br>
Chin<br></span></div>------------------------------------------------------------------------<br><br>_______________________________________________<br>RASMB mailing list<br><a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:RASMB@rasmb.bbri.org" target="_blank">RASMB@rasmb.bbri.org</a><br>
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