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  Thu Aug 4 15:15:32 2016, Aidan, Summary, TempCtrl, RTDs used in aLIGO TCS RHs 
    Reply  Thu Aug 4 18:01:03 2016, rana, Summary, TempCtrl, RTDs used in aLIGO TCS RHs 
       Reply  Fri Aug 5 00:08:16 2016, awade, Summary, TempCtrl, RTDs used in aLIGO TCS RHs 
       Reply  Tue Aug 30 10:56:51 2016, Aidan, Summary, TempCtrl, RTDs used in aLIGO TCS RHs 
          Reply  Mon Oct 10 21:01:52 2016, awade, Summary, TempCtrl, RTDs used in aLIGO TCS RHs 
Message ID: 1702     Entry time: Fri Aug 5 00:08:16 2016     In reply to: 1701
Author: awade 
Type: Summary 
Category: TempCtrl 
Subject: RTDs used in aLIGO TCS RHs 

I assume the key parameters are the noise characteristics here.  They seem to commonly quote the input noise voltage which I'm guessing gives a measure of the equivalent noise injected by the buffer itself. 

Data sheets list the input noise voltage of the BUF634 as 4  nV/√Hz @ 10 kHz . There is another buffer (300 mA), the LMH6321, its datasheet claims  input voltage noise 2.8 for >=10 kHz. I don't know what this means for noise at mHz.

Is there a reason we can't just buffer with more general purpose high current OP Amp? Is the the noise just a killer for that whole catalog of devices? Looking at a random selection, all the ones I've looked at have higher input noise voltage values but the digi-key product selector doesn't let me filter for noise characteristics so maybe there are low noise ones. 

 

 

 

Quote:

The heater driver in the old design (iLIGO PSL) is this horrible programmable power supply with high output noise (see measurement of 40m PSL heater).

What we want instead is something that takes in +/- 10 V and drives a DC current (not PWM) into our heaters (which are ~50-100 Ohms). A BUF634 is almost good enough; it can do 200 mA at 10 V. Is there a BUF634 equivalent which can do more like 500 mA? Otherwise we can just use a opamp + transistor.

What is being used for the ring heaters at the LIGO sites?

 

ELOG V3.1.3-