Campbell Measurement and Control Module CR10 Operator's Manual page 159

SECTION 10. PROCESSING INSTRUCTIONS
Although the algorithm requires an air pressure
entry, the daily fluctuations are small enough
that for most applications a fixed entry of the
standard pressure at the site elevation will
suffice. If a pressure sensor is employed, the
current pressure can be used.
PARAM. DATA
NUMBER TYPE
01: 4
02: 4
03: 4
04: 4
Input locations altered:
*** 58 LOW PASS FILTER ***
FUNCTION
Apply a numerical approximation to an analog
resistor capacitor (RC) low pass (LP) filter using
the following algorithm.
F(Xi) = W*Xi + F(Xi-1) * (1-W)
Where X = input sample, W = user entered
weighting function (O< W <1). If W=O,
F(Xi)=X ; if W=1, F(Xi)=X and F(Xi-1) = output
1
calculated for previous sample
The equivalent RC time constant is given by
T/W, where T is the sampling time in seconds.
For values of W less than 0.25, the analogous
"cut off" frequency (the frequency where the
ratio of output to input is .707) is accurately
represented by W/(2πT). For larger values of
W, this "analog" estimate of the cutoff
frequency becomes less representative.
On the first execution after compiling, F(X) is
set equal to X.
10-6
DESCRIPTION
Input location of
atmospheric pressure
in kilopascals
[PRESSURE]
Input location of dry-
bulb temp. [DB TEMP.]
Input location of wet-
bulb temp.
[WB TEMP.]
Destination input
location for vapor
pressure [VP or Z]
1
PARAM. DATA
NUMBER TYPE
01: 2
02: 4
03: 4
04: FP
Input locations altered:
*** 59 BRIDGE TRANSFORM ***
FUNCTION
This instruction is used to aid in the conversion
of a ratiometric Bridge measurement by
obtaining the value for R
R [X/(1-X)], where X is the value derived by the
f
standard CR10 Bridge Measurement
Instructions (with appropriate multiplier and
offset, Section 13.5) and R
MULTIPLIER value. The result of Instruction
59 is stored in the same location that X was.
PARAM. DATA
NUMBER TYPE
01: 2
02: 4
03: FP
Input locations altered:
*** 61 INDIRECT INDEXED MOVE ***
FUNCTION
Moves input data from location X to location Y,
where X and/or Y are indirectly addressed (X
and Y are stored in the locations specified by
Parameters 1 and 2). If a location parameter is
specified as "indexed" (xxxx--), then the actual
input location referenced is calculated by
adding the current index counter to the value in
the specified input location. When used outside
a loop, the addressing is simply indirect
because the index counter is zero.
DESCRIPTION
Repetitions [REPS]
First input location for
input data [X]
Dest. input location for
first filtered result[F(X)
or Z]
Weighting function, W
[W]
1 for each repetition
which is equivalent to
s
represents the
f
DESCRIPTION
Repetitions [REPS]
Starting input location
& result destination [X]
Multiplier (Rf) [MULT]
1 for each repetition