Here are my notes from this week on the first servicing we've ever done on our Li7500s.
Note that S/N 0813 and 1166 came back from LiCor this summer after being repaired (from lightning damage), so no service was performed on them.
The following all was done using LiCor's software (installed on the Aspire). Before service:
S/N |
Last Cal |
CO2 zero |
CO2 span |
H2O zero |
H2O span |
AGC |
|---|---|---|---|---|---|---|
0813 |
Didn't read |
|
|
|
|
|
1163 |
24 Oct 06 |
0.8697 |
0.9968 |
0.8468 |
0.9946 |
49% |
1164 |
24 Oct 06 |
0.8883 |
1.017 |
0.8601 |
0.9980 |
50% |
1166 |
10 Jul 09 |
0.8896 |
1.0051 |
0.8583 |
0.9969 |
53% |
1167 |
24 Oct 06 |
0.8768 |
0.9978 |
0.8678 |
0.9961 |
48% |
On the afternoon of 10 Nov 09 (after Chris&Jen recovered them from MFO), I dumped the dessicant/scrubber (Magnesium Perchlorate; Ascarite2) from the bottles of 1163, 1164, 1167 and replaced with new Drierite and Ascarite2, following the manual instructions. I put a sticky label on one bottle in each sensor with this replacement date. Instructions say to have the sensors run for at least 4 hours before proceeding with calibrations, so they were all left overnight powered on.
On the afternoon of 11 Nov (~23 hours after changing chemicals), we went through the calibration procedure using a cal lab nitrogen tank for zero CO2 and H2O and a tank I borrowed from Teresa Campos/Cliff Heizer at 404.316ppmV for span CO2. Both of these were supplied to the 7500 using the LiCor calibration tube at a flow rate of about 1.3 lpm. Span H2O was achieved by placing the entire 7500 head in the Thunder chamber at T=25C, RH=80%, which should be a dewpoint of 21.31C. Since the electronics box was outside the chamber, the calibration tube was also placed in the chamber (though not in the optical path) to measure pressure. Since it seemed to take a long time (25 & 50 min, respectively to calibrate 1167 and 1163), we used the calibration tube's temperature reading when we calibrated 1164 the next day. This sped things up a bit. The calibration in the Thunder took long enough that 1164 was done the next morning. The new readings were:
SN |
Cal Date |
CO2 zero |
CO2 span |
H2O zero |
H2O span |
|---|---|---|---|---|---|
1163 |
11 Nov 09 |
0.8709 |
1.0082 |
0.8510 |
1.0229 |
1164 |
12 Nov 09 |
0.8902 |
1.0233 |
0.8635 |
1.0008 |
1167 |
11 Nov 09 |
0.8770 |
1.0207 |
0.8732 |
0.9986 |
AGC values were not logged, but noted to be within 1% of the earlier readings (even with the tube on).
With one exception, these values are higher than before service, indicating more absorption now. I note that I didn't clean the optics prior to this calibration, which probably should have been done, but spot checks of a few of the sensors looked pretty good.
Chris also ran 0813 and 1166 into the chamber (with a dewpoint still at 21.31C) and found that these sensors showed dewpoints of 22.07C and 21.45C, respectively. I'm a tiny bit concerned about this value from 0813.
Note that the LiCor software changed the instrument settings. They will be reset before (re)deployment at MFO.