SHEBA: TRH Messages: 8 Entries..

I note your recent comments that T.plat is higher than T.therm at Atl
and Fla.   I looked back over the data from November and January and
see that for all stations T.plat - T.therm ranges from 0 to 0.2 C.
Steve Semmer reminded me that we had noticed and discussed this
difference previously.

The platinum element is the standard Vaisala 50Y temperature sensor and
is enclosed, along with the humidity sensor, in a porous shield
designed to protect the humidity sensor from contamination.  The
operating range of the platinum sensor does not extend below -40C and
therefore we added the thermistor sensor to measure temperatures below
-40C.  The thermistor is mounted external to the porous shield.

The laboratory calibration of both the platinum and thermistor sensors 
is better than 0.1 C.  We suspect that the platinum temperature sensor
is not dissipating its self-heating as effectively as the thermistor
sensor because the porous shield restricts the heat exchange with the
ambient air.  One useful test of this hypothesis would be to remove the
porous shield from the hygrothermometer at Florida for a day or two.
However, this is not a top priority and could easily wait until Tony
is on site if you do not have time before he arrives.

Please add this explanation to the logbook as a separate entry.

Tom

Between 1130 and 1200 AKST I visited Florida and made changes.
I removed the coaxial intake, knocked out the frost, removed the Goretex
membrane cap, and then reinstalled the coaxial intake.

Yesterday, 25 Feb when the TRH was replaced with the spare TRH the Goretex
cap was left in place. Today, 26 Feb at ~ 1400 AKST when the ATI was sucessfully
deployed, the Goretex cap was removed from the newly installed TRH.

At ~ 1330 AKST the Goretex membrane cap was reinstalled on the TRH
at Florida.
Later iplot showed that: 
   prior to reinstallation T.therm > T.plat
      after reinstallation T.therm < T.plat
This effect has been well demonstrated now by three separate cap switches.

4/11 7:35 AKDT
	Reset TRH heating cycle to on=1, off=1800
	Reason is to determine if that will clean up plot of iload_max
	which is showing the quick heater cycle as a pulse.
	Mostly that is a nusaince on the plot.

As Ed wrote earlier the TRH is acting up.  The new TRH is in the lab and I will replace on the next visit to Baltimore.

Dave

I've found the jack to the fan on the board had come off.  I put it back on
and have been running the unit in the PAM room with the compass attached.
The compass was still erroneous data, values from 240 to 300 (when still).
Can I hook it up to a comm port and talk to it using Procomm?  I checked
out the manual, should I open it and have a looks see?  I will have
to hook it up at Fla to confirm it's deadness. 

The TRH unit that was at Maui:
TRH 006
P1110023  50Y
the compass was KVH P/N 01-0177-0015,  S/N  97060186

I found the coefficients for the TRH that's at Maui now.

dmc

On Sat 9/19 we brought the TRH sensor aboard to troubleshoot the problem
of erroneous temp, RH and compass readings. After plugging the
sensor into the spare box the readings were the same as at Florida. I
allowed the sensor to run during dinner in the hope that if it was
saturated it would dry itself. After dinner the values were identical
to what they had been. I also noticed that the same values were given
after I had unplugged the sensor. Prior to plugging in the sensor the
values were NaN, so why not NaN after. I found that by powering down 
and restarting, the sensor values were correct so I assumed there is a
buffer somewhere that retains the "bad" data until powered down. Is
this the case??

At approx 16:00 AKDT we reinstalled the TRH unit at Florida and all
is well. Tomorrow we will change propane, flash card and TEG nozzle.

Note : The TRH problem also occured at Maui as previously noted. By
this morning Maui was reading proper T, Rh and compass values. I guess
my thought about the buffer isnt correct since Maui fixed itself. Any
ideas??