Operator`s manual

SECTION 8. PROCESSING AND PROGRAM CONTROL EXAMPLES
8-8
14: P95 End
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.
The props can all be measured as single-ended
voltages, but the vertical wind prop calibration
differs from the U and V prop calibration. The
fastest input sequence is to measure both levels
(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 the
most sensitive input range, 5mV,
accommodating a ±80
o
C range between the
measurement and 21X reference junction. The
resolution is (.33µV/(60µV/
o
C) or about 0.006
o
C.
Measuring absolute temperature with TCs
requires a reference junction temperature
measurement. This is measured with Instruction
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 for the
processed results.
TABLE 8.7-1. Example Sensor Description and 21X Multiplier and Offset
DESCRIPTION SYMBOL SENSOR CALIB MEAS TYPE MULT OFFSET
Horiz. Wind U prop 18m/s/V S.E.V. .018m/s/mV 0.0
Horiz. Wind V prop 18m/s/V S.E.V. .018 0.0
Vert. Wind W prop 22m/s/V S.E.V. .022 0.0
Air Temp. Ta TC - TC DIFF. 1.0oC 0.0
Wet-bulb Temp. Tw TC - TC DIFF. 1.0oC 0.0
Vap. Pressure e derived - - - -