corey.gray@LIGO.ORG - posted 08:17, Thursday 05 August 2010 - last comment - 10:13, Tuesday 10 August 2010(121)
Unit#2 Testing Continued
(Corey, Hugh, Jim, Mitch) V3 Sensor Target, V1 Sensor Body swapped, and Gaps Re-set After what happened with V3, it was decided to inspect the target. After inspection, Hugh decided to swap the Target out (too many scratches on its surface for use). While doing the V3 work, a spare Target Body arrived for our V1, so V1 & V3 were both worked on and had their gaps re-set. Sensor Gaps: V3 Has Small Gap Last night I used our teflon shim stock to measure the gap of V1 & V3. Here's an updated list of our gaps (for other Sensors, using values from yesterday): V1: 0.081" H1: 0.083" V2: 0.082" H2: 0.083" V3: 0.072" H3: 0.083" So, V3 is obviously different from the bunch. We'll need to see what to do about this. I'd imagine possibilities are: live with it, electronically change the zero for V3 on the Mini-Rack, or swapping the Target out. Position Sensor Power Spectra With the table locked, took a few power spectra as we did with Unit#1. So, Unit#2 is different in that we have "linked" Mini-Racks for the Position Sensors (they are now tied together with a cable); this was needed to get rid of the 0.3Hz crosstalk we saw on Unit#1. With both Mini-Racks powered ON we had no 0.3Hz noise. To follow Testing instructions, I went ahead and ran two more power spectra (where only one rack was powered at a time). When the Rack#1 (which powers H1V1H2V2) was only powered ON, H1V1H2V2 looked real and H3V3 looked like noise. When Rack#2 was only powered ON, all the Sensors looked like noise; you could sot of see something from H3 & V3, but it was not very discernable. As for the H3 & V3 counts, their value went up from a few hundred counts to 4000 counts. So, it looks like with linked racks, you can't see Rack#2. (the first attachment shows spectra with BOTH Mini-Racks ON, and with Rack #1 ON....the Rack#2 ON measurement wasn't interesting) The second plot I'm posting is the spectra for the Position Sensors & GS13s with the table Locked & Unlocked. The third plot is a comparison in spectra of the GS13's between Unit#1 & Unit#2. These data files have been put on the svn at: /opt/svncommon/seisvn/seismic/HAM-ISI/X1/Data/unit_2/dtt
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Forgot to add a gap check Jim W. made on V3. Here's what he found: "It does look low. .075 was tight, .070 slid in easy." So, let's say the gap is now: 0.074". We'll be addressing this issue by adjusting the electronic zero on the mini-rack (via pot) and and then re-setting the gap.