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DI
Disk Recording
DI causes data to be recorded in the directory as specified in the OP_ST.FIL found in the
Brewer program directory. Data recording may be turned off if the data disk is nearly full, if
the data disk specified is not installed, or if the NR command has been sent. If recording is
turned off, the screen will display "DISK TURNED OFF" on the screen in place of the
"BYTES" message, and must be turned on with DI. See also the NR command.
DS
Direct Sun Ozone Observation
DS results in an O
source. The Brewer Zenith Prism and Azimuth Tracker are oriented toward the sun, the Iris
is closed, FW#1 is rotated to the Ground Quartz Disk (position 1), and FW#2 is adjusted for
optimum intensity (starting from position 2). Data is recorded on disk and is printed as
previously determined by PN, PD, or PF commands.
A DS observation consists of five sets of 20 cycles of the slit mask (a measurement), each
cycle taking a reading for 2*0.14 seconds on each wavelength. Intensity data for six
wavelengths, and the dark count, is recorded for each of the five measurements.
The Azimuth and Zenith positions are updated after each measurement.
After each measurement O
processed, resulting in a single summary set for the total observation.
As a safety feature to prevent damage to the detector, the measurement may terminate if, as
a result of varying cloud conditions, FW#2 has initially been set to a low attenuation value
and clouds suddenly move out of the field of view.
A DS measurement takes slightly approximately 2.5 minutes to complete.
Details of the data as recorded in the raw data (B) file, and the summary data as recorded in
the summary (S) file can be found in Appendix A.
DSP Dispersion Test
DSP allows for the collection of data for a dispersion test analysis wherein absorption
coefficients, wavelength vs. step number and resolution vs. step number equations for each
slit is determined.
This is a command generally reserved for factory use or for use during an instrument
recalibration if it is suspected that constants are incorrect
DSSUM Direct Sun Data Summary
DSSUM reads the daily Data (B) file and printouts out the summary of the day's DS
measurements. An entry is also made to the OZOAVGYY.nnn and NOAVG.nnn file. The
DSSUM command is usually executed as part of the ED command.
See also Appendix.
DT
Dead Time Measurement
Dead Time is a measure of how long a photon counting circuit is "dead" (or cannot count a
second photon) after a first photon has been detected. Incorrect dead time values can result
in errors in intensity values, especially at high count rates. The dead time for each instrument
is manually record in the Instrument Constants File and can be seen on the PO command
printout.
Dead time differences of greater than 5% should be investigated.
For this test the iris is open, FW#1 is put to position 1. Measurements are made at high
intensities (FW#2=0), and at low intensities (FW#2=1).
Dead time test results are recorded in the DTOAVG or DTNAVG files, and DT is usually
invoked as part of the ED sequence.
See Appendix F and Appendix.
36
(or NO
) observation being taken using the direct sun as a radiation
3
2
(or NO
) is calculated. After the fifth measurement all data is
3
2
MKIV OPERATOR'S MANUAL
.
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