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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

Pressure2

GPIO-MM Clock Calibrations

Prior to AHATS, a calibration of the 20 MHz clocks on each of the diamond GPIO-MM-12 cards was performed using the rubidium referenced signal generator in the NCAR EOL sounding lab.

The reference frequency was stepped in 10 KHz increments from 110 to 300 KHz approximately every 10 seconds. The GPIO cards were configured to count the number of  tics from the onboard 20 MHz clock while counting 10,000 cycles of the reference input, which is the same manner that the frequencies of the ParoScientific temperature transducers are sampled. These counts are repeated every 0.1 seconds.  The resulting frequency measurements were then compared against the reference frequencies.

See the attachments to this blog for plots of the calibrations.

The upper left plot shows the linear relation between the mean error in the frequency measurement and the reference frequency.

The slope of the least squares linear fit to the data is a correction for the 20 MHz clock on the GPIO-MM:

corrected clock frequency = 20 MHz / (1 + slope)

The upper right plot is the measurement error after applying the corrected 20MHz clock rate to the data.

Lower left is a plot of various measurement errors. The top black points are the frequency discretizaion due to a difference of one 20 MHz clock tic. As you can see, below  a 200 KHz input frequency the resolution is better than 1 part in 10⁶, which is the target accuracy for sampling the ParoScientific 202BGs.  The temperature signal from a 202BG is around 170 KHz and the pressure signal is around 40 KHz, so a 20 MHz clock is able to provide this accuracy.

*max(abs(fcor-fref))*is the maximum absolute difference of the measured, clock corrected frequency from the reference frequency for the 100-300 samples at each reference frequency. This maximum error seen in the test stayed below the 1:10⁶line except for some points at frequencies over 200 KHz. Board 3 in pressure2 was the exception and did have some points over the line.  We should repeat the calibration after the project.

The maximum error also generally stayed below the frequency discretization level, suggesting that after the clock is corrected, almost all of the remaining error is due to the discretization.  Boards 1,2 and 3 however do show some errors above the discretization level.

mean(fcor-fref) are the mean measurement error  points at each frequency.

The lower right plot shows the number of samples at each frequency. The tests were sometimes performed more than once, or with more than one input pulse counter, hence we usually have more than the 100 samples expected over 10 seconds.

The effect of temperature on the on-board 20 MHz clock is not known.

AHATS daily status 7/16/08

Staff: Semmer, Horst, McIntyre, Khoung

For more details, see the ahats logbook at https://wiki.ucar.edu/display/ahatslogbook

Good wind direction: From July 11, 12:00, through July 16, 12:00, we have
had 61.08 hours or 51% good wind directions with continuous periods
of at least 25 minutes.  This includes 43.33 hours stable data and
16.92 hours unstable.  Note that more than half of the stable data
is weakly stable, 0 < z/L < 0.1.  With the exception of this near-neutral
data, the balance between stable and unstable is more closely balanced
than the numbers suggest.

Local data storage:
------------------
root@upwind root# df | grep usb
/dev/sda1             57685532   2377044  55308488   4% /var/tmp/usbdisk
root@downwind1 root# df | grep usb
/dev/sda1             57685532   2878296  54807236   5% /var/tmp/usbdisk
root@downwind2 root# df | grep usb
/dev/sda1             57685532   3114884  54570648   5% /var/tmp/usbdisk
root@profile root# df | grep usb
/dev/sda1             57685532   1951096  55734436   3% /var/tmp/usbdisk
root@pressure1 root# df | grep usb
/dev/sda1              3897204    630656   3266548  16% /var/tmp/usbdisk
root@pressure2 root# df | grep usb
/dev/sda1              3940812    630240   3310572  16% /var/tmp/usbdisk

Pressure:
--------
(+/- = ~1 std deviation among variables at the same height)

p: ok, +/- 0.02 mb
p'p': ok, +/- 0.002 mb^2
w'p': ok, +/- 0.002 m/s mb
t: ok, +/- 0.3 degC
Pref: ok, range = +/- 2 mb, with a period of ~24 hours

Profile:
--------

h2o: ok, 13 gm/kg
w'h2o': ok, 0.02 m/s g/m^3 at midday
co2: ok, 15 mmol/m^3
w'co2': ok, -0.01 m/s mmo/m^3 at midday

ASTER and ISFF were stopped and rebooted around 12:30 PDT, July 16, to move power to two new UPS's.

AHATS daily status 7/15/08

Staff: Semmer, Horst, McIntyre, Khoung

For more details, see the ahats logbook at
https://wiki.ucar.edu/display/ahatslogbook

Good wind direction: From July 11, 12:00, until July 15, 12:00, we have had 43.7 hours or 46% good wind directions with continuous periods of at least 25 minutes.  This includes 32.67 hours stable data and 10.08 hours unstable.
Local data storage:
------------------
Swapped all local data storage media yesterday.

Pressure:
--------
(+/- = ~1 std deviation among variables at the same height)

p: ok, +/- 0.02 mb
p'p': ok, +/- 0.002 mb^2
w'p': ok, +/- 0.004 m/s mb
t: ok, +/- 0.3 degC
Pref: ok, range = +/- 2 mb

Profile:
--------

diag: ok
samples.sonic: ok
spd: ok
dir: ok
w: ok
tc: ok
w'w': ok
u*: ok
sigma_w/u*: ok (1.3 at night)
w'tc': ok
T: ok
RH: 4m may be low by on the order of 1% RH
P: okay

Upwind (hts=3.3):
----------------

diag: ok
samples.sonic: ok
spd: ok, +/- 14 cm/s (6u has +15 cm/s offset in u)
dir: ok, +/- 3 deg
w: ok, +/- 7 cm/s
tc:  ok, +/- 0.17 deg
w'w': ok, +/- 0.01 m^2/s^2  (30 min avg for second moments)
u*: ok,  +/- 2 cm/s
sigma_w/u*: ok (1.3 at night)
w'tc': ok, +/- 0.02 m/s degC
tc'tc': ok, +/- 0.05 degC^2

Downwind Lower (hts=3.3):
------------------------

diag: ok
samples.sonic: ok
spd: ok, +/- 20 cm/s
dir: ok, +/- 6 deg
w: ok, +/- 6 cm/s
tc:  ok, +/- 0.25 deg
w'w': ok, +/- 0.01 m^2/s^2  (30 min avg for second moments)
u*: ok,  +/- 3 cm/s
sigma_w/u*: ok (1.3 at night)
w'tc': ok, +/- 0.02 m/s degC
tc'tc': ok, +/- 0.08 degC^2

Downwind Upper (hts=4.3):
------------------------

diag: ok
samples.sonic: ok
spd: ok, +/- 20 cm/s
dir: ok, +/- 5 deg; 6t is about 6.5 degrees off from profile sonic
w: ok, +/- 6 cm/s
tc:  ok, +/- 0.2 deg
w'w': ok, +/- 0.01 m^2/s^2  (30 min avg for second moments)
u*: ok,  +/- 3 cm/s
sigma_w/u*: ok (1.3 at night)
w'tc': ok, +/- 0.02 m/s degC
tc'tc': ok, +/- 0.07 degC^2

AHATS daily status 7/14/08

Staff: Semmer, Horst, McIntyre, Khoung

Summary: Max temperature yesterday at z=1.5m, 97 degF.

For more details, see the ahats logbook at https://wiki.ucar.edu/display/ahatslogbook

Good wind direction: From July 11, 12:00, until July 14, 12:00, we have
had 33.5 hours or 47% good wind directions with continuous periods
of at least 25 minutes.  This includes 24.75 hours stable data and
8.17 hours unstable.

Local data storage:
------------------
Swapped all local data storage media today.

Pressure:
--------
(+/- = ~1 std deviation among variables at the same height)

p: ok, +/- 0.02 mb
p'p': ok, +/- 0.002 mb^2
w'p': ok, +/- 0.004 m/s mb
t: ok, +/- 0.3 degC
Pref: ok, range = +/- 2 mb

The usbdisks at profile, downwind1, pressure1, and pressure2 were swapped at ~12:00 local. Will do downwind2 and upwind after lunch.

Downwidn1 and upwind swap at ~ 16:15.

Steve bumped the switch on the power strip used for the computers  and  hard disks around 7:26 am, July 14, causing the isff2 and isff3 to stop archiving data. We rebooted aster around 9:57 am.

The output message from the ambient pressure was changed to 3 decimal places like the pressure reference. This occurred at 15:20 local time.

AHATS daily status 7/13/08

Staff: Semmer, Horst, McIntyre

Summary: Max temperature yesterday at z=1.5m, 98 degF; seems even cooler today.

<w'p'> is max around 14:00 PDT at about -0.015 m/s mb; much smaller at night.
<u'p'> and <v'p'> (in sonic coordinates) have comparable magnitudes.
d<w'p'>/dz max is about -0.005 mb/s

For more details, see the ahats logbook at https://wiki.ucar.edu/display/ahatslogbook

Good wind direction: From July 11, 12:00, until July 13, 12:00, we have
had 25.17 hours or 52% good wind directions with continuous periods
of at least 25 minutes.  This includes 18.75 hours stable data and
6.08 hours unstable.  The past 24 hours has had a good run of proper
wind directions.

Local data storage:
------------------
Swapped all local data storage media yesterday.

Pressure:
--------
Note that dat("p") + dat("Pref") - dat("P") ~ 0.1 mb.

This is on the order of the absolute accuracy of the Vaisala barometers.
I would have expected this difference to be negative and correlated with
wind speed^2 to reflect the residual dynamic pressure errors of the
PAM pressure port.  However the difference is the wrong sign and is not
correlated with wind speed.  Apparently this is the combined offset
errors in the two Vaisala barometers.

(+/- = ~1 std deviation relative to others)
p: ok, +/- 0.02 mb
p'p': ok, +/- 0.002 mb^2
w'p': ok, +/- 0.003 m/s mb
t: ok, +/- 0.3 degC
Pref: ok, range = +/- 2 mb

I repositioned the downwind1 gps antenna around 11:30 am, July 13.  I moved it from the top of the adam, where it was under one of the horizontal braces of the PAM tripod, to the top of the brace near the gps antenna for pressure1.

Wireless communication has not been good since the switch to the AP24. So we have changed back to the 180 antenna and will see if things improve. There has been an improvement in the SNR since the antenna cable length was reduced.

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.

Tom noticed we had noisy data throughout the night, so I reduced the tx-power of the AP24 from 25 to 20. Based on data_stats the noise has gone away. This dropped the SNR from high 40s to 40. Will monitor.

Due to the on/off wireless today we decide to download the local storage after the AP24 system was back up. All ADAMS had their disks swapped.

Due to the wireless outages we decided to move the .14 network to the AP24 internal antenna. This took place over the course of today. Since the mast had to lowered , wires run, changes to the Ap24 firmware, etc. As a result the SNR from downdwind2 and profile has almost doubled. The tx-power ion the internal was set to 25, gain to 0.

A backup configuration for the previous configuration and the new one were created. They can be found in the AP24 directory file.

Alico-11072008-2300.backup (old)

Alico-12072008-2252.backup (new)

network address for AP24:

internal: 192.168.14..251

external 192.168.12.251