40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  PSL  Not logged in ELOG logo
Entry  Tue Jun 22 18:02:32 2010, Frank, Misc, RefCav, heater-to-can time constant StepResponse_Heater-Can.png
    Reply  Wed Jun 23 03:24:30 2010, rana, Misc, RefCav, heater-to-can time constant 
Message ID: 173     Entry time: Wed Jun 23 03:24:30 2010     In reply to: 172
Author: rana 
Type: Misc 
Category: RefCav 
Subject: heater-to-can time constant 

In the entry below, Frank meant to add some commentary explaining that he thinks this long time constant is anomalously long.

At the 40m, it is much shorter. The insulation there is much thinner, and the can is somewhat shorter, but I think the main effect is that the steady state temperature of this can is too low. The temperature setpoint should be set to 35-40 C.

Then the time constant can be remeasured by doing a small step (~1 deg). We can't assume linearity over 10 deg - what we care about is the small signal time constant at the quiesscent temperature. Although the heating time and the cooling time will be slightly different, they will be comparable for small steps.

If the quiesscent temperature is set to be equal to the room temperature, it is insanity. We need to count on the room acting as a conductive and convective cold load since we only have a heater for an actuator and not a cooler.

ELOG V3.1.3-