Of course, I now think that many pressure spikes are now real events (e.g. dust devils). However, I've seen other spikes (mostly upwards) that aren't real. Further tracking finds that most are (only?) spikes in the Paro's temperature measurement. These spikes are always positive. During 10 Aug, most of these were with t.8b, however I also see them on 5b, 9b, 10b, 7t, and 8t. These are not exclusively on pressure2, nor are they all the channels on pressure2. Also,…
To follow-up on the leak check yesterday (which showed a slow leak), I repeated this test today:
1033 P=1004.88 (pinched off)
1034 unpinched Pref (so I could read pressure easily) P=1007.29
1037 installed tee, P=1007.32
1038 blew in, P= 1029 dropping
1039 pinched entire array, P=1025 still dropping
1041 tighten tee, P=1021.5 still dropping
1043 pinched off 11b P=1018.9, still dropping
~1100-1113 reseated both reservoir endcaps with more Teflon tape and plumbers' grease.…
between 1440 - 1522, Khoung tried the pinch test again, removing all of the array of tubing. During this test, the overall noise in p[ref].11b was significantly less, indicating that part (but not all) of the p' problems still are tubing related.
At 1525, he sucked on the reservoir and reconnected the (entire) tubing. It appears that the tubing has a leak with a time constant of about 10min. This was actually desirable(!), but indicates that we still have some sleuthing to do.
Still trying to work several problems:
P.0m is only 1Hz, only about same resolution as Pref, so not much help monitoring Pref after all. Thus, change back to monitor Pref with 11b's 202BG
Data from P.0m yesterday showed Pref fluctuations. Try to damp these by removing potential leak (old capillary leak) and add more steel wool.…
At 1512, I pinched off the entire reference pressure tubing so that both Pref and P.0m measured just the reference volume. (It turned out that P.0m's RS232 connector fell off, so we didn't get data from it for any of these tests .)
At 1618, I opened the above, but pinched off lines to only connect 6b.
At ~1745, I opened the above connecting the entire tubing system, but pinched off Pref (after reconnecting the P.0m signal).…
pressure1
pressure2
w302859
w302821
w302828
w302829
w302832
w302826
w302871
w302874
w302835
w302842
This is the list with viper on the top and the power supply on the bottom.
Also see https://wiki.ucar.edu/display/ahatslogbook/2008/07/17/GPIO+boards+in+pressure+systems https://wiki.ucar.edu/display/ahatslogbook/2008/07/17/GPIO+boards+in+pressure+systems
I notice in the p' time series a drop of pressure at 1323 this afternoon. This looks like the signature of a dust devil to me (and I saw one earlier today near the trailer).
To further diagnose the p' system, I've been wanting to set up an independent system like CHATS. Now that John has brought out another pressure sensor, we made the following changes between 1030-1200:
- Installed the cal-lab field reference Paro 760 to measure Pref (in lieu of the 14th 202BG). Added it to profile:ttyS17 as P.0m.
- Changed the 14th 202BG (still known as p.11b.4.8m) to measure just like CHATS, between the Bedard port through the hose and the CHATS reference.…
All of the reference line tubing was insulated between 0800-0840 this morning.
Based on one spectrum, it doesn't look like this has made much of a difference. Does this mean <yet> something else is going on to cause these Pref fluctuations?
Tonight we should receive another Pref sensor. Tomorrow I intend to use it as the new Pref sensor and configure my current Pref sensor (the 11b 202BG) exactly as done in CHATS.</yet>…
After discussions with John Wyngaard over the last 2 days (and a wake-up call this morning), we decided to try to lower at least the high frequency fluctuations in Pref by trying to add a sleeve around the tubing. John had the great idea to use foam pipe insulation. We found some in Hanford and added it to the horizontal sections of the array when it was down for sonic leveling today. Unfortunately, I had only purchased enough for a test this morning,…
Here is an example from yesterday (1700-1730) of spectra (top panel) and cospsectra (bottom). The black line in the top panel is the spectrum of just the reference pressure (not connected to the atmosphere in any way). The red lines are all the sensors at 5m. Low frequencies in the reference pressure are due to drift in the CHATS reference volume due to changing soil temperature. Note that the signal-to-noise ratio from 0.01 to 1 Hz is on the order of one. (Actually,…
At my request, Steve just pinched closed the leak I added yesterday to the AHATS pressure reference system. I hadn't seen much reduction of the high frequency temperature fluctuations in the Pref signal since this leak was introduced. (Though it definitely had an affect on the low frequencies, where P and Pref were perfectly correlated.
This was done about 10:11am.
From about 1635-1735 I reconfigured pressure yet again. (See 11b signal for exact times.)
- 11b transducer removed and inserted into the CHATS system (which was buried yet again) to monitor Pref (in parallel with the Vaisala PTB220).
- a leak installed into the far end of the AHATS reservoir (black tube). About 4m of the 1/16" line is attached, mostly coiled up in the ground, but the open end is exposed.
We'll see what <this> looks like...
We built a 26-liter volume out of 2 5' lengths of 4" ABS pipe, stuffed it with steel wool and buried it in the ground (after checking that there were no leaks). We disinterred the N2 cylinder. After the usual 2 hours, Pref has settled down. I <do> think the signal is better behaved than for any of the other volumes, however there still are fluctuations that are larger than the static pressure signal (by about an order of magnitude in the power spectra between 0.01 and 1.0 Hz).</do>…
The results of this morning's tests indicate that the "medium frequency" signals we've been seeing in the pressure spectra are from the reference! This may be caused by convection in the cylinder that Jim Wilczak warned us about. Since we don't have a perfect alternative at the moment, we've just plumbed all the references to the CHATS reference. Unfortunately, we had to disinter and rebury this reference in order to connect to it.
6b and 6t are now returned to their original configurations.…
To diagnose our strange p' spectra problem, I've made 2 changes:
6b - the + side is now plumbed through the CHATS garden hose to the Bedard quad-disk-probe, which I've lashed to the top of the tripod in the middle pitchfork position. Good winds at this location are bit restricted due to the config#3 towers that Steve has erected, but should give us some idea. Changes done 0915-0930.…
Okay, I've been looking at pressure data and I can't figure out some things:
1. The reference pressure is slowly ramping away from P. My best guess is that the soil surrounding the reservoir is actually cooling now that it has the space blanket on top of it, thus making the pressure go down. I believe that this is consistent with the sequence of operations (from Khuong) when the cylinder was reburied (hole dug Fri AM, old hold dug up Fri AM, cylinder moved to new hole Fri AM,…
Tom said to note that, upon tear-down of configuration #1 (wide array), the pressure ports appeared to swivel a bit on the 1/4" bolt securing them to the booms. Thus, the separation vector between the ports and sonic arrays could be different. The bolts were tightened by inserting a washer in configuration #2.
(comment entered by Steve Oncley, but page was logged in as Gordon -- now I know better...)
These are the serial numbers of the Diamond GPIO-MM-12 cards used in each pressure system, along with the clock rates that were determined for each card. Following the tables is a discussion of the clock rate calibration procedure. Plots of the clock calibrations are viewable as attachments, under the Tools menu.
Pressure1
board
SN
corrected clock rate (Hz)
0
302859
20,000,292.73
1
302828
20,000,450.67
2
302832
20,000,284.66
3
302871
20,000,072.66
4
302835
20,000,242.…
The output message from the ambient pressure was changed to 3 decimal places like the pressure reference. This occurred at 15:20 local time.
The output format of the pressure sensor attached to the pressure reference tank was changed to 1/1000. Also the running average was changed to 30 seconds to provide better resolution. The output rate was left at 1 second.
UPDATE: The averaging was set back to 1 second since we can average the data in post processing.
Steve completed sealing the fast pressure lines July 11 at 10:30 am PDT. He used teeny cable ties on all the junctions. The system passed an over-pressure leakdown test by maintaining a constant pressure.
A separate test was done on the reference tank. It also had a leak at the junction to the tank. This was fixed at 12:00 noon.
A pressure check was done after modifying 4 sensors. There was improvement but the leak still existed. Decided to go back to square one by checking the Vaisala line. It was ok. Leakage started as soon as we added the first "T" junction. Further tests showed that the leak could be stopped by adding panduit ties at each junction (3 ties per T). This requires very small ties so an order to Digikey was placed. Should have the ties by tomorrow noon.
After getting the wireless link from downwind2 and profile going this morning we did not realize that pressure1 was also down. It was restarted late this afternoon.
Note by Gordon: this system was still configured to use dhcp - and it lost its lease when the etherants were down. Fixed.
A variety of pressure tests were conducted on the pressure lines. Th first was a check of the reference cell. There appeared to be a very slow leak. The main line was tested a major leak was found. It was at the end of the line where a tee was instead of a straight coupler. This was fixed around 2:30 pm.; We will see what happens over the next few hours.
The interface board being used for 11B had a bad RJ45 connector. This was fixed and the board was installed at Pressure2. PARO 11B was attached and data looks good. This occurred around 10:00am local.
A modified interface board for 11B, Pressure2, was added this morning. Based on Gordon's data_dump function the pressure and temperature data looked good with little noise.
In order to investigate whether the reference pressure system is working correctly, the Vaisala barometer was removed from the profile tower and installed next to the reference pressure tank. It is connected to the reference tube via a 1/16 inch T connector near where the line goes underground to the tank. The barometer data cable is connnected to ttyS17 on downwind2. The pressure variable is called Pref. The data appears at 18:22 PDT, Jul 8. So,…
Yesterday, July 6, in the afternoon we installed the pressure1 system, with the altered interface cards, and mounted the Paroscientific units on the masts. Data from pressure1 appears at 15:30 PDT. All frequency counts look good. The units serviced by pressure1 are 3b,4b,5b,5t,6b,6t and 7t.
No data was being sent from pressure2, and local storage was not being written to. System was up, could log in over the network, and the dsm process was running.
data quit at 12:26 UTC, Jul 1. Restarted it with adn/aup at 13:26 UTC.
Chenning and Khuong working on the pressure measurement system at these times:
June 27, 2008:
Morning. Hung the horizontal pressure reference line.
4:45-5:15 PM. Working on the 1/4 in tubing, connecting them to the pressure transducers.
June 28, 2008
9:00-11:00am. Put 1/16 in couplers to the transducers on the lower array. The tubing on the transducer is hard and the coupler cannot be inserted directly, a heat gun was used to melt the tubing in order to insert the coupler.…
Specific Sonic Locations; Wide Array:
Note: Sensors shown in table organized from Southwest end of array to the Northeast end of the array.
UpWind Array of PAM tripods (spacing nominally 4m, array line parallel to and 16m NW from 'downwind').
SW
NE
horiz index
11
10
9
8
7
6
5
4
3
3.2m sonic s/n
1122
1123
1121
673
1119
674
677
536
539
upwind serial port
11
10
9
8
7
6
5
2
1
DownWind Array of PAM tripods (spacing nominally 4m).…