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ID Date Author Type Categoryup Subject
  1698   Wed Jun 24 12:09:24 2009 ClaraUpdatePEMWeek 1(ish)

I spent the week reading up on filter algorithm theory, particularly Wiener filtering. I have also learned how to get data from specific channels at specific times, and I've been getting myself acquainted with Matlab (which I have not previously used). Finally, I started messing around with the positioning of the accelerometers and seismometers in order to try to find the setup that yields the best filtration.

  1703   Thu Jun 25 21:00:30 2009 ClaraUpdatePEMMC1 Accelerator set moved again; new XLR cables

I moved the MC1 set of accelerators. Might have bumped things. If things aren't working, look around the MC1 chamber.

Also, I constructed two new XLR cables, but have not tested them yet.

  1704   Fri Jun 26 15:22:28 2009 ClaraUpdatePEMXLR cables tested and labeled

We now have two 80-foot, female-to-female XLR cables for our pretty new microphones, one yellow and one purple. They have been tested and appropriately labeled.

Also, here is a very helpful pdf for how to properly attach the XLR connectors to a raw quad cable, as well as one for how to put the actual connectors together (ignore the cable instructions on the connector page... the cable depicted is not a quad cable).



  1705   Fri Jun 26 18:00:36 2009 JenneUpdatePEMNew PEM channels for the fancy-pants new microphones

[ Jenne, Clara ]

We made new channels for the microphones which came in this week, by editing C1ADCU_PEM.ini (and making an appropriate backup before we modified it) then restarting the framebuilder and the frontend computer C0DCU1.  The new channels are:



These are connected to channels 13 and 14 on the PEM ADCU board, just next to the GURALP seismometer channels.


Clara is testing the mics so the max output voltage can be limited to +-2V for the DAQ, then we'll hook them up to our new channels and listen to the IFO (and all the audio frequency noises around it).

  1707   Sat Jun 27 02:48:09 2009 ClaraUpdatePEMI moved accelerometers and made some pretty pictures

I have been working on finding the best spots to put the accelerometer sets in order to best subtract out noise (seismometers next!). Here is a plot of what I've done so far:


All of these were 80-minute samples. The dashed line is unfiltered, solid line filtered. So, Setup #1 looks the best so far, but I didn't leave it there very long, so perhaps it was just a really awesome 80 minutes. I've put the accelerometers back in the Setup #1 position to make sure that it is really better.

And, in case you can't intuitively figure out what configuration the accelerometers are in by such descriptive names, here are some helpful pictures. I didn't know about the digital cameras at first, so these are actually sketches from my notebook, which I helpfully labeled with the setup numbers, color-coded to match the graph above! Also, there are some real-life photographs of the current arrangement (Setup #1' if you forgot).




Doesn't this one look kind of Quentin Blake-esque? (He illustrated for Roald Dahl.)


This is the MC1 set.


Guess which one this is!

  1708   Sat Jun 27 03:16:16 2009 ClaraUpdatePEMExciting microphone things!

So, I'm double-posting, but I figured the last post was long enough as it was, and this is about something different. After double and triple checking the XLR cables, I hooked up the microphone setup (mic---preamp---output) to the oscilloscope to figure out what kind of voltage would register with loud noises. So, I clapped and shouted and forgot to warn the other people in the lab what I was doing (sorry guys) and discovered that, even on the lowest gain setting, my loud noises were generation 2-3 times as much voltage as the ADC can handle (2V). And, since our XLR cables are so freaking long, we probably want to go for a higher gain, which puts us at something like 20 times too much voltage. I doubt this is really necessary, but it's late (early) and I got camera-happy, so I'm going to share anyway:


So, to deal with this issue, I made some nifty voltage dividers. Hopefully they are small enough to fit side-by-side in the ports without needing extra cableage. Anyway, they should prevent the voltage from getting larger than 2V at the output even if the mic setup is producing 50V. Seeing as my screaming as loud as I could about 2mm away from the mic at full gain could only produce 45V, I think this should be pretty safe. I put the ADC in parallel with a 25.5 kOhm resistor, which should have a noise like 10^-8 V/rHz. This is a lot smaller than 1 uV/rHz (the noise in the ADC, if I understood Rana's explanation correctly), so the voltage dividers should pose a noise issue. Now for pictures.


I opened one so you can see its innards.


In case the diagram on the box was too small to decipher...

And finally, I came up with a name scheme for the mics and pre-amps. We now have two Bluebird (bacteriophage) mics named Bonnie and Butch Cassidy. Their preamps are, naturally, Clyde and The Sundance Kid. Sadly, no photos. I know it's disappointing. Also, before anyone gives me crap for putting the labels on the mics upside-down, they are meant to be hung or mounted from high things, and the location (and stiffness) of the cable prevents us from simply standing them up. So they will more than likely be in some kind of upsidedownish position.

  1713   Thu Jul 2 05:27:12 2009 ClaraUpdatePEMVoltage Divider Oops

I tested the voltage dividers and was getting up to about 3V. I retested the mic w/o the voltage divider in place, and, lo and behold, I was able to generate about 70-75V (previously, I maxed out at 45V). I'm not 100% sure why this was, but it occurs to me that, before, the sounds I was generating were short in duration (loud claps, short yelps). This time, I tried yelling continuously into the microphone. So, probably, I simply wasn't seeing the real peak before on the scope because it was too short to pick up. I have corrected the voltage dividers (by replacing the 25.5 kOhm resistors, which were in parallel with the ADC, with 10 kOhm resistors, taking the voltage ratio to ~60:1) and tested them. I haven't been able to generate more than 1500 mV, so I think they are safe. (It's possible we would have been fine with the old setup, since I think it would be hard to get any noises as loud as I was making, but better safe than sorry, right?)

I'm attaching a diagram of the new-and-improved voltage dividers.


  1714   Thu Jul 2 06:31:35 2009 ClaraUpdatePEMFirst mic in place and connected

I clamped Bonnie (microphone) to the top of a chamber near the vertex of the arms and placed Clyde (pre-amp) on the table right below (see picture). The cable was laid and Bonnie and Clyde are plugged into port #13 on the ADC. The second cable was plugged into port #14, but it is not connected to anything. I placed the looped up cable on top of the cabinet holding the ADC.

Note: the angle in the photograph is such that we are looking along the y-arm.

  1715   Thu Jul 2 16:45:06 2009 ClaraUpdatePEMBonnie and Clyde are officially in operation! (Butch Cassidy and the Sundance Kid are in temp position)

I hooked up Bonnie and Clyde last night and tested it today. First I tried some loud noises to make sure I could identify them on the readout. Then, Steve suggested I try to look for some periodic stuff. I set up Butch Cassidy and the Sundance Kid on the cabinets by the MC2 optic. Now for graphs!



I tapped on the microphone a few times. I also yelled a bit, but this is sampling by seconds, so perhaps they got overwhelmed by the tapping.


This time I tried some more isolated yells. I started with a tap so I'd be sure to be able to recognize what happened. Apparently, not so necessary.


Here, it looks like a pretty strong periodic pattern on the second mic (Butch Cassidy). I replaced the lines with dashed ones where the pattern was a little less clear. Possibility interference from something. Mic1 (Bonnie) seems to show a pretty regular beat pattern, which seems reasonable, as it isn't particularly close to any one instrument fan.


So, anyway. I thought those were neat. And that I wanted to share.


  1723   Wed Jul 8 12:36:15 2009 ClaraUpdatePEMCoherences and things

After setting up the microphones last week, I modified the Wiener filtering programs so as to include the microphone signals. They didn't seem to do much of anything to reduce the MC_L signal, so I looked at coherences. The microphones don't seem to have much coherence with the MC_L signal at all. I tried moving Bonnie to near the optical table next to the PSL (which isn't in a vacuum, and thus would, presumably, be more affected by acoustic noise), but that didn't seem to make much of a difference. Eventually, I'd like to put a mic in the PSL itself, but I need to work out how to mount it first.


Bonnie's new location.

You can see in bonnie_butch.pdf that none of the mic signals are giving very good coherence, although they all seem to have a peak at 24 Hz. (In fact, everything seems to have a peak there. Must be a resonant frequency of something in the mode cleaner.)

I've also attached plots of the coherences for all six accelerometers and the three Guralp seismometer axes. I plotted the most coherent traces together in the last pdf: the y-axes of the MC2 accelerometer and the two seismometers (the Ranger measures ONLY y) and, interestingly, the z-axis of the MC2 accelerometer. Unsurprisingly, the seismometers are most coherent at the low frequencies, and the MC2-Y accelerometer seems to be coherent at very similar frequencies. The MC2-Z accelerometer, on the other hand, seems to be coherent at the higher frequencies, and is highly complementary to the others. I am not really sure why this would be...

Finally, I was curious about how the noise varies throughout the day, because I didn't want to mistakenly decide that some particular configuration of accelerometers/seismometers/whatever was better than another b/c I picked the wrong time of day to collect the data. So, here is a plot of Wiener filters (using only accelerometer data) taken over 2-hour intervals throughout the entirety of July 6, 2009 (midnight-midnight local).


It's a little bit confusing, and I should probably try to select some representative curves and eliminate the rest to simplify things, but I don't have time to do that before the meeting, so this will have to suffice for now.

  1726   Wed Jul 8 19:42:37 2009 ClaraUpdatePEMBonnie moved to PSL, getting some coherence with the PMC_ERR channel

In her position overlooking whichever table it is that is next to the PSL, Bonnie drummed up some decent coherence with the PSL-PMC_ERR channel, but not so much with the MC_L. I moved her into the PSL itself, and now there is rather good coherence with the PMC_ERR channel, but still not so great for MC_L.


Bonnie's new home in the PSL.

  1727   Thu Jul 9 02:18:09 2009 ranaUpdatePEMBonnie moved to PSL, getting some coherence with the PMC_ERR channel
My guess is that we need a different acoustic strategy. The microphones are mainly for high frequencies,
so you should not expect any coherence with MC_L (or even better, MC_F) below 100 Hz. I expect that the
main coherence for MC_F will come from the PSL in that band.

After subtracting that one out, we should look at the signal from the lock of the X or Y arm, and see
if we can nail that by putting a mic right above the AS table (leaving enough room to take the lid off).
If that works OK, we can find a spot under the lid and se if it gets better.
  1728   Thu Jul 9 19:05:32 2009 ClaraUpdatePEMmore mic position changes; mics not picking up high frequencies

Bonnie has been strung up on bungees in the PSL so that her position/orientation can be adjusted however we like. She is now hanging pretty low over the table, rather than being attached to the hanging equipment shelf thing. Butch Cassidy has been hung over the AS table.

Moving Bonnie increased the coherence for the PMC_ERR_F signal, but not the MC_L. Butch Cassidy doesn't have much coherence with either.

I noticed that the coherence would drop off very sharply just after 10 kHz - there would be no further spikes or anything of the sort. I used my computer to play a swept sine wave (sweeping from 20Hz to 10kHz) next to Butch Cassidy to see if the same drop-off occurred in the microphone signal itself. Sure enough, the power spectrum showed a sharp drop around 10kHz. Thinking that the issue was that the voltage dividers had too high impedance, I remade one of them with two 280 Ohm and one 10 Ohm resistor, but that didn't make any difference. So, I'm not sure what's happening exactly. I didn't redo the other voltage divider, so Bonnie is currently not operating.


  1729   Thu Jul 9 19:24:50 2009 ranaUpdatePEMmore mic position changes; mics not picking up high frequencies
Might be the insidious 850 Hz AA filters in the black AA box which precedes the ADC.

Dan Busby fixed up the PSL/IOO chassis. WE might need to do the same for the PEM stuff.
  1744   Tue Jul 14 16:31:46 2009 ClaraUpdatePEMFrequency Response of Microphone (Bonnie)

So, I actually took these measurements last week, but I didn't get around to making nice plots and things until now. I figured the time while I wait for the spectrum analyzer to do its thing was a good time.

Having been unable to locate the SR785 and also unsure how to connect it to a computer speaker (and also unable to find a free one), I downloaded a demo of a function generator onto my computer and just used that. (Same thing I used to do the swept sine that created the frequency power response plots I posted last week.) I set the program to a number of different frequencies and had the other end of the cable hooked into the oscilloscope to see a) if I could pick out the frequency and b) see how the magnitude of the microphone output varied with the frequency.

The first set of measurements I took, I didn't realize that I could increase the output power of the function generator. Because the generated sound at the default setting was relatively quiet, the oscilloscope traces were pretty chaotic, so I usually froze the trace so that I could look at it better. I ended up with a lot of weird jumps in the magnitude, but I later realized that there was a lot of beating going on at some frequencies, and the amplitude changes were probably much more drastic for the -20 dB sounds than the 6 dB sounds, since it was closer in amplitude to the surrounding noises. So, I've included that data set in my plots for the sake of completeness, but I'm pretty sure that it is useless.

Once I realized I could increase the power output for the signal generator, I took a set of data with and without the voltage divider at 6 dB. There was a cluster of frequencies that showed significant beating around 1700-3000 Hz in the data WITH the voltage divider, but I did not see any clear beating in the data WITHOUT. In the plots, I simply plotted up the highest and lowest amplitudes I measured for the frequencies with significant beating, since it was obviously hard to tell what the amplitude would have been without any background noise. In the w/o volt. div. set, although I didn't see any obvious beat patterns, the measured amplitudes did jump slightly at the frequencies that showed beats with the voltage divider. So, perhaps I was just not seeing them, but they influenced my amplitude measurements? I'm not sure if it would be possible for the voltage divider itself to cause beat frequencies.

 (Note: the amplitudes measured were from zero to peak, as the oscilloscope I was using wouldn't show a big enough vertical range to easily measure the peak-to-peak voltage difference.)

I've attached two plots of my measurements. One has a regular x-scale and includes all the measurements. The second has a logarithmic x-scale and omits the 20 Hz points. I had some troubles being able to pick out the 20 Hz signal on the oscilloscope... I don't know if my computer speakers just don't work well at that frequency or what, but either way, those points seemed highly suspect, and omitting them from the log plot allowed me to spread things out more.

One thing I'm not sure about is the 3000 Hz point. It was one of the ones with a beat frequency (~130 Hz), and the amplitudes were pretty low. The corresponding point from the non-voltage-divider data set is also low. So, I'm not sure what's happening there.

The one thing that I do think is quite clear is that the 1000 Hz drop-off in power when the microphone is connected to the ADC has nothing to do with the voltage divider. Beat issues aside, the shapes are very similar (pay no attention to the absolute scale... obviously, the voltage responses with and without the voltage divider were very different, and I just scaled them to fit in the same plot).

Update: Jenne pointed out that I was not absolutely clear about the voltage scale in my plots. The GREEN and BLUE points are on a mV scale, and the RED points are on a 10mV scale. I should probably redo the plots in Matlab in eventuality, since Excel is hard to use if you want to do anything that is not extremely basic with your plots, but this was my solution for the time being. So, the fact that the RED points, which are the data taken WITHOUT the voltage divider, are lower than the GREEN ones does not in any way indicate that I measured lower voltages when the voltage divider was not used.

Also, a to do list:

- Many of the beat frequencies I picked out were veeeeery slow, indicating that something is going at a frequency that is very close to the arbitrary frequencies I chose to sample, which is a little strange. That, combined with the fact that I saw clear beats with the voltage divider but not without leads me to believe that it may be worth investigating the frequency response of the voltage divider itself.

- Redo the measurements near the anomalous 3000 Hz point with a higher density of sampled frequencies to try to see what the heck is going on there.

  1757   Thu Jul 16 10:52:58 2009 ClaraUpdatePEMSingle Channel TRS-RNC Cable

I made and tested a female-to-female TRS(audio)-RNC cable. It only has a single channel, so it won't work for stereo speakers or anything, but I should only need one speaker for testing the microphones. The tip of the plug is the signal, the sleeve is ground, and the ring is null.

  1760   Fri Jul 17 18:04:54 2009 ClaraUpdatePEMGuralp Box Fail

I've been trying for most of the week to get noise measurements on the output of the Guralp box as well as scross the AD640 chip. The measurements haven't really been making sense, and, being at a loss as to what else I should try, I decided to redo the resistors on the N/S 2 and E/W 2 channels. (I had been comparing the VERT1 and VERT2 channels, as VERT1 has been restuffed and VERT2 has not.) I don't need all three of the second set of channels to do more measurements, so it seemed like a good use of time.

The first thing I noticed was that the VERT2 channel was missing two resistors (R24 and R25). I probably should have noticed this sooner, as they are right by the output points I had been measuring across, but it didn't occur to me that anyone did anything to the VERT2 channel at all. So, probably the measurements on VERT2 are no good.


Note the existence of 100 kOhm resistors on the top channel, and none on the bottom channel (VERT2).


Then, while I was soldering in some 100 Ohm resistors, I happened to notice that the resistors I was using had a different number (1001) on them than the corresponding ones on the already redone channels (1003). I checked the resistance, and the ones on the already redone channels turned out to be 100 kOhm resistors, rather than 100 Ohms. So, I double checked the circuit diagram to make sure that I had read it correctly, and there were a number of resistors that had been relabeled as 100 Ohms and several relabeled as 100 kOhms. On the board, however, they were ALL 100 kOhms. Clearly, one of them is wrong, and I suspect that it is the circuitboard, but I don't know for sure.



The diagram clearly shows that R6 should be a 100k resistor, while R5 and R8 should be 100 Ohm resistors, but they are all the same (100k) on the board. I suspect this may have something to do with larger-than-expected noise measurements. But, it's possible the diagram is wrong, not the board. In any case, I didn't really know what to do, since I wasn't sure which was right, so I just replaced all the resistors I was sure about and removed the 100k and 100 Ohm resistors without replacing them with anything. Incidentally, the box of 100kOhm resistors seems to be missing, so I wouldn't have been able to finish those anyway.

  1761   Sat Jul 18 19:49:48 2009 ranaUpdatePEMGuralp Box Fail
That's terrible: R5 & R8 should definitely be 100 Ohm and not 100kOhm. 100k would make it a noise disaster. They should also be metal film (from the expensive box, not from the standard box). This is the same for all channels so might as well stuff them.

The circuit diagram between TP3 and TP4 appears to be designed to make the whitening not work. That's why R6 & R7 should be 100k. And R2 should be metal film too.

Basically, every time we want good low frequency performance we have to use the metal film or metal foil or wirewound resistors. Everything else produces a lot of crackling noise under the influence of DC current.

I'm also attaching the voltage and current noise spectra for the AD620 from the datasheet. These should allow us to compare our measurements to a reasonable baseline.
  1765   Mon Jul 20 17:06:29 2009 JenneUpdatePEMGuralp Box Fail

That's terrible: R5 & R8 should definitely be 100 Ohm and not 100kOhm. 100k would make it a noise disaster. They should also be metal film (from the expensive box, not from the standard box). This is the same for all channels so might as well stuff them.

The circuit diagram between TP3 and TP4 appears to be designed to make the whitening not work. That's why R6 & R7 should be 100k. And R2 should be metal film too.

Basically, every time we want good low frequency performance we have to use the metal film or metal foil or wirewound resistors. Everything else produces a lot of crackling noise under the influence of DC current.

I'm also attaching the voltage and current noise spectra for the AD620 from the datasheet. These should allow us to compare our measurements to a reasonable baseline.

While we're comparing things to other things, Ben Abbott just emailed me his measurement of the AD620 from back in the day. Clara's going to use this along with the specs to make sure that (a) we're not taking crazy measurements and (b) our AD620s aren't broken and in need of replacement. In this plot, we're looking at the GOLD trace, which has the AD620 set up with a gain of 10, which is how our AD620's are set up in the Guralp breakout box.

Just picking a single point to compare, it looks like at 1Hz, Ben saw ~130dBVrms/rtHz. Converting this to regular units [ 10^(#dB/20)*1Vrms = Vrms ], this is about 3*10^-7 Vrms. That means that Clara's measurements of our AD620 noise is within a factor of 2 of Ben's. Maybe the way we're connecting them up just isn't allowing us to achieve the ~50nV/rtHz that is claimed.
  1767   Tue Jul 21 13:55:08 2009 ClaraUpdatePEMGuralp Box Success!

There managed to be just enough 100 kOhm resistors to stuff all the "2" channels (VERT2, N/S2, E/W2) with the fancy low-noise resistors. The first six channels (VERT 1/2, NS 1/2, EW 1/2) are now completely done with the thin-film resistors, taking into account the changes that were made on the circuit diagram. I also replaced the C8 capacitor with the fancy Garrett ones and added capacitors on top of R4 and R13 (after painstakingly making sure that the capacitances are exactly the same for each pair) for the "2" channels. It looks like the capacitors on the "1" channels are the cheaper ones. I will compare the noise measurements later to see if there is any difference - if so, I can replace those as well (although, we're out of the 1 uF capacitors needed for C8).

Speaking of, we are now out of or very low on several types of the Garrett resistors/capacitors: 1 uF, 1kOhm, 100 Ohm, 14.0 Ohm, and 100 kOhm. I left the specifics on Steve's desk so that more can be ordered for the eventual time when the third set of channels needs to be restuffed.

  1800   Tue Jul 28 16:03:14 2009 ClaraUpdatePEMGuralp Seismometer cable pin diagram

I mapped out the corresponding pins on both ends of the Guralp seismometer cable. Here is the diagram:


The circular 26-pin end of the cable (that plugs into the seismometer) is labeled as above. The other end (the 39-pin end) is not physically numbered, so I just came up with a numbering system. They are both pictured on the non-cable end of the connector. The colored circles indicate the pin pairs.


FROM JENNE, 30JULY2009:  the Dsub end is 37 pin, not 39.

  1806   Wed Jul 29 13:15:35 2009 ClaraUpdatePEMDents = Bad??

I was in the lab last night accelerometerizing and noticed some dents on the tubes that stick out horizontally from the MC2 optical chamber (sorry, I don't know what they're called or what they do). One of them is pretty big... I don't know if this is a problem, but it probably isn't a good thing. Photos below:




This last one is a little hard to see... I was having trouble getting a good angle on it, but it's there. Not quite as significant as the first one though. (The first two pictures are of the same dent.)

  1808   Wed Jul 29 14:56:44 2009 JenneUpdatePEMMiniEarthquakes due to construction

The construction people next door seem to be getting pretty excited about pounding things lately.  At my desk the floor was shaking like a mini-earthquake, and all of the accelerometers were pretty much railed. Clara has the Guralp box out right now, so the Guralp is unplugged, but the Ranger didn't seem to be railed.

This either (a) is part of the reason the MC is being wonky lately, or (b) has nothing whatsoever to do with it.  The MC watchdogs haven't been tripping all the time, so maybe this isn't a primary cause of the wonky-ness.

In looking at a many-days/months trend to see how far back this has been going, it looks like the accelerometers are hitting their rails pretty much all day every day.  This may be significantly hindering Clara's Wiener filtering work.  I think the gain on the accelerometer's controler panel is already set to 1, but if it's set to 10, we may want to reduce that.  Alternatively, we may want to put in attenuators just as the signal is entering the PEM ADCU, to help reduce the amount of rail-hitting that's going on. I don't remember this from a couple of months ago, so this may be a problem that will go away once the construction / landscaping is done next door.

  1811   Wed Jul 29 19:46:04 2009 rana, albertoUpdatePEMDents = Bad??
It looks like the MC2 chamber and/or stack has been jarred and shifted. Please be careful and use much less force and speed around the MC2 chamber.

My guess is that the work with the accelerometers around there had made the MC2 angle and
position change last night. The reason that we don't see it in the OSEMs so much is that its
a change in the actual stack position and tilt.

To recover, we changed the MC2 alignment bias to get the beam through the Faraday. This did NOT get
the beam back onto the right place on the MC TRANS QPD. For tonight we decided to not recenter that
since Rob might not like this position. We did, however, zero out the MC WFS and the PSL POS/ANG.

If the interferometer locking is OK tonight, then we (Steve and whoever else is here at 7 AM)
should recenter IP POS and IP ANG and also fix up the PSL POS and PSL ANG QPDs. You can see
in the attached picture that there are two problems to fix:
1) The knobs (circled in red and blue) are wrapped in foil. Why???
2) The handedness of the mirror mount with the orange arrow is wrong. This should be unmounted and clocked
by 90 deg. Right now the beam is nearly clipping on the mount. Also, we need to change the channel names
on the PSL POS (or maybe its ANG). It has the horizontal/vertical channels misnamed.
  1859   Fri Aug 7 16:53:35 2009 ClaraUpdatePEMGuralp breakout box noise, finally

After many issues, I finally have some Guralp box noise. I did not measure every single channel with high resolution at the low frequencies because that would have taken about 3 years, but I could perhaps take some faster measurements for all of them if necessary.



  1866   Fri Aug 7 20:43:35 2009 Clara, Jenne, Rana, JanUpdatePEMTwo Guralps plugged in, prepped for huddle test

Both Guralps and the Ranger have been placed in our nice new insulated foam box, complete with packing peanuts, in the corner between the x and y arms. The Guralp breakout box has been reinstalled and everything is plugged in in prepartion for the huddle test. However, we're having some issues with ADC channels, which will be worked out tomorrow (hopefully) so that data can be collected over the weekend.

Currently, one Guralp is plugged into the three SEIS-MC1 channels. We made new channels for the second Guralp (GUR-EW, GUR-NS, and GUR-VERT), but had issues with those. So, EW and NS have been plugged into PEM_AUDIO-MIC1 and MIC2 for the time being.

  1868   Sat Aug 8 17:19:07 2009 ranaUpdatePEMTwo Guralps plugged in, prepped for huddle test

 I found that several of the cables are unlabeled so I'm not sure what's plugged in. In the end, I found that the TEMP_2, _3, & _44 channels were working and so I plugged in anything that looked seismic into there.

TEMP_2 is now apparently the X channel of the 2nd Guralp. If someone can figure out which cable belongs to the Y channel, please plug it into TEMP_3 and then we can fix the channel names.

I also removed (gently) all of the accelerometers from MC2's chamber. This didn't break the lock, but I intentionally broke it to make sure it reacquired fine. It did and the MC TRANS QPD showed no significant shift afterwards.

  1869   Sat Aug 8 17:23:29 2009 ranaUpdatePEMoffensive 2 Hz sine wave removed

Friday, we were seeing a 2 Hz harmonic series in all of the PEM channels. Today I found that some bad person had put in a 4V (!) signal into one of the channels with a signal generator. The generator was also sneakily stuck way back inside the DCU rack. NO SECRET SIGNAL INJECTIONS!

Since the ADC has a 2Vpk range, this was saturating and putting in harmonics in all the adjacent channels. I disconnected it and turned off the function generator.

  1872   Mon Aug 10 14:58:01 2009 JenneUpdatePEM2nd set of Guralp channels plugged into ADCU

The second set of Guralp channels is now plugged into the PEM ADCU, into channels which are confirmed to be working.  (Method: 1Vpp sine wave into channel, check with DataViewer).


Direction, Channel Name, .ini chnum, BNC plug # on ADCU

Vertical: C1:PEM-SEIS_GUR_VERT, 15023, #24

N/S (should be Y when the seismometer is put in place): C1:PEM-TEMP_2, 15001, #2

E/W (should be X when the seismometer is put in place): C1:PEM-TEMP_3, 15002, #3


There is IFO work going on, so I don't want to rename the channels / restart fb40m until a little later, so I'll just use the old TEMP channel names for now. 


There is something totally wrong with the E/W channel.  I can look at all 3 channels on a 'scope (while it's on battery, so the op-amps in the breakout box aren't grounded), and VERT and NS look fine, and when I jump around ("seismic testing"), they show spikes.  But the EW channel's signal on the 'scope is way smaller, and it doesn't show anything when I jump. 


I might use the handheld Guralp tester breakout box to check the seismometer.  Also, a suspicion I have is that whoever put the box back in on Friday night after our final noise measurements left the inputs shorted for this one channel.  It's the 3rd channel in the set, so it would be most likely to be stuck shorted...  Investigations will ensue.

  1882   Mon Aug 10 18:12:25 2009 JenneUpdatePEM2nd set of Guralp channels plugged into ADCU


The second set of Guralp channels is now plugged into the PEM ADCU, into channels which are confirmed to be working.  (Method: 1Vpp sine wave into channel, check with DataViewer).


Direction, Channel Name, .ini chnum, BNC plug # on ADCU

Vertical: C1:PEM-SEIS_GUR_VERT, 15023, #24

N/S (should be Y when the seismometer is put in place): C1:PEM-TEMP_2, 15001, #2

E/W (should be X when the seismometer is put in place): C1:PEM-TEMP_3, 15002, #3


There is IFO work going on, so I don't want to rename the channels / restart fb40m until a little later, so I'll just use the old TEMP channel names for now. 


There is something totally wrong with the E/W channel.  I can look at all 3 channels on a 'scope (while it's on battery, so the op-amps in the breakout box aren't grounded), and VERT and NS look fine, and when I jump around ("seismic testing"), they show spikes.  But the EW channel's signal on the 'scope is way smaller, and it doesn't show anything when I jump. 


I might use the handheld Guralp tester breakout box to check the seismometer.  Also, a suspicion I have is that whoever put the box back in on Friday night after our final noise measurements left the inputs shorted for this one channel.  It's the 3rd channel in the set, so it would be most likely to be stuck shorted...  Investigations will ensue.

 All the channels are now good, and all the names are back to making sense. 

The problem with EW2 was in fact that the alligator clip used to short the inputs during the noise test Friday night was left in the box.  Not great, but now it's taken care of, and we have recorded data of the noise of the breakout box, so we can include that in our plots to see if we're at the limit of how good we can do at subtracting noise.


The channels are now named thusly:

C1:PEM-SEIS_GUR_VERT  (BNC input #24, .ini channel #15023)

C1:PEM-SEIS_GUR_EW     (BNC input #3, .ini channel #15002)

C1:PEM-SEIS_GUR_NS      (BNC input #2, .ini channel #15001)

C1:PEM-SEIS_MC1_X         (BNC input #11, .ini channel #15010)

C1:PEM-SEIS_MC1_Y        (BNC input #12, .ini channel #15011)

C1:PEM-SEIS_MC1_Z       (BNC input #10, .ini channel #15009)

C1:PEM-SEIS_MC2_Y (Ranger, which for the Huddle Test is oriented VERTICALLY)   (BNC input #4, .ini channel #15003)


Now we wait.....and tomorrow extract the noise of each of the seismometers from this!



  1885   Tue Aug 11 02:15:20 2009 ClaraUpdatePEMGuralp breakout box circuit diagram

While writing my progress report, I redrew the Guralp breakout box circuit diagram with all the changes marked. Since only one hard copy exists, I thought it might be useful to post my drawing up in case it is needed for any reason. The two drawings are the same - the second has just been broken into two parts to make it easier to fit on a normal 8.5 x 11 or A4 sheet of paper. The gains for each opamp have not been marked, but they could very easily be added in if necessary. The black resistances and capacitances are the originals. All changes have been indicated in blue.



  1897   Thu Aug 13 09:22:06 2009 ranaUpdatePEMranger

Rana, Jan, Jenne

We noticed that the Ranger data was all bogus at low frequencies. So we checked it and found that the proper procedure had not been used when changing it from horizontal to vertical last week. So the huddle test data from the weekend is not valid for the ranger; we will have to repeat it sometime.

So we used the manual, and extended the hanger rod on top of the Ranger to free the mass. It now has good response and coherence with the Guralps down to 0.1 Hz. See attached plot soon.


  1898   Thu Aug 13 11:20:43 2009 janoschHowToPEMthree-channel self-noise estimation

There are two new Matlab files on the svn in /mDV/extra/C1. 'mycsd.m' is to calculate the cross-spectral density between two channels, 'csd_40T_40T_SS1.m' calls this function with the available seismic channels and derives a self-noise spectrum for the vertical axis using all three seismometers. The method requires that there are no correlations between two instruments only which is a bad idealization for certain frequencies if you have seismometers of totally different types.

'mycsd.m' uses the high-gain, low-resolution Nuttall window (built-in Matlab function 'nuttallwin.m'). High-gain windows are used for broad-band spectra like seismic spectra, but it should be exchanged by another window if you plan to look at small-bandwidth features like peaks.

Since the three-channel analysis does not require knowledge of response functions, it could be used to evaluate the performance of the adaptive filter. For example, if three channels responding to the same signal are available, then the ratio of any two csds corresponds to one of the relative transfer functions. You can then compare this function with the result produced by the adaptive filter.

  1900   Fri Aug 14 02:57:46 2009 ClaraUpdatePEMRedo of the Huddle Test

I put all three seismometers and all six accelerometers together in the foam box with peanuts. Three of the accelerometers are facing in the x-direction and three are in the y-direction. Both Guralps are aligned on the NS axis and the Ranger is pointing vertically.

**EDIT: The accelerometers are in the x and z directions, not x and y. Sorry, I was sleepy when I wrote this.**

One of the accelerometers was refusing to show anything, and after a few hours of checking connections and swapping cables, I discovered that someone had unplugged the cable from the ADC. A quick glance in the dataviewer shows that the channel has been unplugged since about 3 in the afternoon on August 8th (Saturday). So... obviously all the accelerometer measurements made with that channel since then did not actually get recorded. Yay.

Anyway, as of 2:45, everything is working and taking data. Clearly we're not getting a full night's worth... hopefully that's okay.

  1918   Mon Aug 17 07:01:09 2009 ClaraUpdatePEMADC noiseness

I shorted the inputs on three channels and the outputs on three channels of the Guralp box, and I did similar things with the accelerometers. I was going to move the instruments themselves back, but I didn't have time, so they are still in the box in the corner. If the setup could stay as-is for at least a few hours, that would be awesome.

  1933   Fri Aug 21 17:28:50 2009 Kevin, ranaSummaryPEMMagnetic Field Measurements Around the Lab

This goal of this test was to measure and map the AC (at 60 Hz) and DC magnetic fields around the interferometer. I've attached the final products which were drawn up with Google SketchUp.

The notes on the maps make them more or less self explanatory: for each numbered point there's an X, Y, and Z measurement produced by the magnetometer. For the AC numbers I measured the Peak-to-Peak value, while for the DC I simply measured the Mean. The magnetometer's axes were always oriented about the same way, with the X arrow on the magnetometer pointing north. I tried to keep variables such as the lights constant as much as possible (they were all on for most measurements, with the exception of a few noted DC ones) and all measurements had the top of the magnetometer at about 32 inches.  The map is pretty close to scale and all the walls and numbered locations were measured out (though the location of objects and the laser tubes is somewhat estimated). I added "landmarks" in the room, which were pretty much the laser tubes, computer racks, and ISC tables.

For each laser room measurement I also took a screenshot using the oscilloscope as a means of recording the shape of the wave for each measurement. Ch1 corresponds to the X value, Ch2 to the Y, and Ch3 to the Z. The screenshots are numbered 1-29 corresponding to the numbers on the map. The zip folders containing the screenshots can be found on the wiki:  PEM:Magnetometers

I should also mention that there is no point #24 and accordingly no 24 screenshot. I realized after I was done that I had messed up the location of that one and instead of risking bad data decided to just remove it.

I decided on the location of the points mainly based on the location of outlets in the room (since I had to plug in the oscilloscope for the AC numbers to set it to 60 Hz). After an initial pass of the room, I went back and filled in some of the larger gaps by moving the magnetometer as far as I could while the oscilloscope remained plugged in to the wall. I used the same points for DC numbers.

Prior to measuring the laser room, I measured the field in other rooms as well. I have

  • AC numbers and screenshots for the control room and the adjoining office room.

  • DC numbers for the entry room and the office room, not including the control room. The X-axis arrow is pointed south (instead of north) for these numbers.

These numbers were sort of a warm up for me to figure out the process and how I would go about recording my data. Since they're not in really important locations and aren't guaranteed to be accurate, I decided not to map them, though the screenshots are still on this Dell Inspiron 1300 Laptop and the measurements in my notebook.

Here are the settings I used on the oscilloscope for all measurements (I merely changed the Vertical Coupling between DC and AC depending on what I was measuring):

  • Impedance: 1M ohms

  • Bandwidth: Full

  • Probe Setup: Voltage 1X

  • Trigger Type: Edge

  • Trigger Coupling: DC

  • Fast Trig: Normal

  • Trigger Mode: Auto

  • Trigger Source: AC Line

  • Acquire Mode: 512 Average

 The notebook that I used contains some additional info that I didn't include in the map, most importantly more precise descriptions of where each of the points is located and the measured distance between each of them (as well as slight changes I made to my measured distances in order to make the room a rectangle; the changes are slight enough that they shouldn't have any real effect on the data).

Since Kevin used our 3-axis Bartington Fluxgate magnetometer, we can guess that we can convert his voltage measurements (below) into magnetic field
by using the manual's guess of 10 uT /V or 10 V/Gauss. This is probably ok at the factor of 2 level, but one day we should calibrate it with a coil.

The punchline is that the DC fields in the lab are roughly what we expect from the Earth's field plus the rebar in our floors: ~1 Gauss. The 60 Hz fields are ~50-500 nT peak-peak.

  1964   Thu Sep 3 10:19:35 2009 steve, albertoUpdatePEMparticle counts and burning hillsides

The San Gabriel mountain has been on fire for  6 days. 144,000 acres of beautiful hillsides burned down and it's still burning.  Where the fires are.

The 40m lab particle counts are more effected by next door building-gardening activity than the fire itself.

This 100 days plot shows that.

  1975   Tue Sep 8 17:57:30 2009 JenneUpdatePEMAll the Acc/Seis working again

All of the accelerometers and seismometers are plugged in and functional again.  The cables to the back of the accelerometer preamp board (sitting under the BS oplev table) had been unplugged, which was unexpected.  I finally figured out that that's what the problem was with half of the accelerometers, plugged them back in, and now all of the sensors are up and running.

TheSEIS_GUR seismometer is under MC1, and all the others (the other Guralp, the Ranger which is oriented vertically, and all 6 accelerometers) are under MC2.

  1987   Tue Sep 15 15:46:05 2009 steveUpdatePEMPEM and VAC

FSS_RMTEMP is moving up and  daily fluctuations  are  less . 120 and 16 days plots are below.

  2078   Fri Oct 9 17:41:04 2009 JenneUpdatePEMAccelerometers relocated

[Sanjit, Jenne]

The set of 6 accelerometers which were semi-randomly placed underneath the MC2 tank are now back into 2 separate sets of 3 - one set at MC2 and one set at MC1.  The channel names once again reflect reality, i.e. MC1_Y is actually under the MC1 tank, and aligned with the y direction.  Also, the Guralp under MC1 was moved a little bit to the left, because Sanjit wanted to put the accelerometers where the seismometer had been. 

  2079   Sun Oct 11 04:12:44 2009 ranaUpdatePEMAccelerometers relocated

Some of these channels are not like the others.

  2119   Mon Oct 19 17:12:54 2009 jenneUpdatePEMaccelerometers and seismomters are all good.


Some of these channels are not like the others.

 All of the PEM channels seem to be okay right now.  The accelerometers didn't turn out to have any differences in the traces when we put both XYZ triplets right next to each other, so we put them back where they belong.  Gur2 seismometer was showing a few problems, especially with Gur2_X, as Rana posted in elog 2079.  This was solved by tightening the cable screws which hold the Dsub end of the Guralp cable to the front panel of the Guralp box.  All is now well.

  2150   Tue Oct 27 17:58:25 2009 JenneConfigurationPEMUnknown PEM channels in the PEM-ADCU?

Does anyone know what the channels plugged in to the PEM ADCU, channels 5,6,7,8 are?  They aren't listed in the C1ADCU_PEM.ini file which tells the channel list/dataviewer/everything about all the rest of the signals which are plugged into that ADCU, so I'm not sure if they are used at all, or if they're holdovers from some previous time.  The cables are not labeled in a way that makes clear what they are.  Thanks!

  2156   Wed Oct 28 14:39:10 2009 steveUpdatePEMafter the tour of the 40m
Illuminators and PSL lights turned off.
HEPA filter speed increased from 20 to 100%
  2170   Mon Nov 2 15:27:08 2009 JenneUpdatePEMGur2 cables have been moved

The cables labeled "Gur2" which were connected to channels 2,3,4 of the PEM-ADCU have been moved to the PCIX ADC which is connected directly to the ASS machine.  This means that until I (a) put the cables back or (b) figure out how to route channels from the ASS ADC to the RFM, we won't be able to use these channels for environmental monitoring, nor will they be saved. 

The Gur2_X, Gur2_Y, Gur2_Z channels are now connected to the 2nd, 3rd and 4th ADC channels respectively, on the ASS ADC (the first channel / TP1 is ADC0_0, which is the 1pps signal.).  The sketchy thing about the setup is the connection between the cables and the new ADC board.  The PCIX card is connected to the ASS via a white ribbon cable, and the board is just sitting on top of the computer box.  The 1pps (which has been hooked up for a long time) goes into the board via clip-doodles.  The regular channels have a SCSI cable connector, so I used a SCSI cable to connect up the ADC tester board, and connected my seismometer inputs to this tester board via more clip doodles.  Clearly this is a sketchy solution, and not okay for more than a day or so.  But we'll see how it goes. 

I'm going to, on the SimuLink Diagram, change the input source of these channels, from the RFMN to the ADC.  Then we'll see if that fixes our timing problem, and magically makes everything relating to the OAF work, and subtract huge amounts of noise. 

  2191   Fri Nov 6 09:17:53 2009 steveOmnistructurePEMPSL HEPAs turned on

The PSL enclosure HEPAs turned on at 30%

  2194   Fri Nov 6 16:27:15 2009 JenneUpdatePEMRanger moved

The Ranger seismometer has been moved to ~the middle of the Mode Cleaner tube, and it's orientation has been changed to horizontal (using all of the locking/mass centering procedures).  This is similar in orientation to the way things were back in the day when Rana and Matt had the OAF running nicely.

  2206   Mon Nov 9 01:52:56 2009 ranaUpdatePEMcoherence v. time for 2 accelerometers

I used the coh_carpet.m function from the mDV to calculate this plot:

coh_carpet('C1:PEM-ACC_MC1_X','C1:PEM-ACC_MC2_X',gps('now - 3 days'),3600*12,4,10,64)

It shows the coherence v. time of two of our X-direction accelerometers starting around 1AM on Friday and going for 12 hours.

I'm not sure what it means exactly, but it looks like the coherence is relatively steady as a function of time. I will need more RAM than Rosalba or a smarter code to calculate longer time stretches.

  2223   Mon Nov 9 19:09:09 2009 JenneUpdatePEMNoise floor of the Ranger Seismometer

To estimate the noise floor of the Ranger, Rana and I locked the mass on the seismometer, so there will be no (aka minimal) signal from the motion of the ground in the pickup coil.  We should be seeing primarily the noise of the readout electronics.  We also put the Ranger on top of one of the foam lids from the Seismometer Isolation Boxes to further isolate from ground motion (this didn't change the signal noticeably).  

In this plot, Green is the locked-mass-on-foam noise floor, blue is the regular spectra, with the SR560 AC coupled, and the red is the regular seismic spectra with the SR560 DC coupled.  There doesn't seem to be a noticeable difference between blue and red (the spectra were taken at different times of day, with the red taken at night, when we generally expect things to be quieter).  I'm leaving the SR560 DC coupled.  (Rana had found it earlier this afternoon GND coupled....not sure yet why).

Also, we're not sure that the green curve is true readout noise, vs. how much of it is specifically due to the fact that the mass is locked down.  Especially around a few hundred Hz, the green curve is much higher than the other 2, and at a few tens of Hz there is some weird peak action.  However, this will be okay as a first-run noise estimate for the Ranger's noise floor.

The question at hand is: Do we need to redo any of the Ranger's readout electronics (i.e. replace the SR560 with a Pomona Box circuit) to lower the noise floor, or is it okay as-is?

  2237   Wed Nov 11 12:50:10 2009 JenneUpdatePEMSeismometer Noise Characteristics

The attached plot shows the spectra of the 3 Z axes of the 3 seismometers we have (this data is from ~20Aug2009, when the Ranger was in the Z orientation) in Magenta, Cyan and Green, and the noise of each of the sensors in Red, Blue and Black.  The noise curves were extracted from the spectra using the Huddle Test / 3 Corner Hat method.  The Blue and Black traces which are just a few points are estimates of the noise from other spectra.  The Blue points come from the Guralp Spec Sheet, and the Black comes from the noise test that Rana and I did the other day with the Ranger (elog 2223).  

I'm not really happy with the black spectra - it looks way too high.  I'm still investigating to see if this is a problem with my calibration/method....

ELOG V3.1.3-