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SECTION
8.
PROCESSING
AND PROGRAM CONTROL EXAMPLES
15:
P
End
Table
3
8.7
COVARIANCE CORRELATION
PROGRAMMING EXAMPLE
The'example is a 2 level meteorological tower
with 5 sensors at
each
level.
The three
components of the wind
are measured using
prop
anemometers. Two thermocouples
(TC)
are used to measure ambient and wet-bulb
temperatures and calculate water vapor
pressure
on-line. All
sensors are scanned once
per second (1 Hz) and
a
5 minute averaging
period with
a
30 minute Output Interval
is
specified. The example optimizes the input
measurement sequence for speed and shows
the instructions necessary to provide calibrated
inputs, properly ordered
to produce the desired
outputs from
the Covariance Correlation
(CV/CR)
Instruction. Table 8.7-1 groups the
sensors according
to measurement type and
gives the
21X multiplier and offset.
DESCRIPTION
Horiz.
Wind
Horiz.
Wind
Vert.
Wind
Air Temp.
SENSOR
prop
prop
prop
TC
TC
derived
Wet-bulb Temp.
Vap. Pressure
The props
can all be measured as single-ended
voltages, but the
verticalwind prop calibration
differs from
the
U
and V prop
calibration. The
fastest input sequence
is
to measure both
(6 props)
with
a
single instruction using
the
U
and
V
calibration and correct the W
measurements with
the Fixed Multiply,
Instruction
37.
The
type
E
thermocouples are measured
on
most sensitive input range, 5mV,
accommodating
a t80oO range between the
measurement and
21X reference
junction.
The
resolution is (.33pV/(60pVPC) or about 0.006oC
Measuring absolute temperature with TCs
requires
a reference junction temperature
measurement. This is measured with
17.
The specified outputs determine
the input order
required by the
CV/CR Instruction. Table 8.7-2
lists the desired outputs from the
two levels
along with
the Input Storage locations tor the
processed results.
14:
TABLE 8.7-1. Example Sensor Description and 21X Multiplier and Offset
SYMBOL
0.0
0.0
0.0
0.0
0.0
U
v
w
Ta
Tw
e
CALIB
18m/sA/
18m/slV
*v:*
MEAS TYPE
s.E.v.
s.E.v.
s.E.v.
TC DIFF.
TC DIFF.
MULT
.018m/s/mV
.018
.o22
1.OoC
1.0oC
8-8
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