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

DESCRIPTION

01:

4

Input location of

 

 

atmospheric pressure

 

 

in kilopascals

 

 

 

[PRESSURE]

02:

4

Input location of dry-

 

 

bulb temp. [DB TEMP.]

03:

4

Input location of wet-

 

 

bulb temp.

 

 

 

[WB TEMP.]

04:

4

Destination input

 

 

location for vapor

 

 

pressure

[VP or Z]

Input locations altered:

1

 

*** 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)=X1; if W=1, F(Xi)=X and F(Xi-1) = output 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.

PARAM.

DATA

 

 

NUMBER

TYPE

DESCRIPTION

 

01:

2

Repetitions

[REPS]

02:

4

First input location for

 

 

input data

[X]

03:

4

Dest. input location for

 

 

first filtered result[F(X)

 

 

or Z]

 

04:

FP

Weighting function, W

 

 

 

[W]

Input locations altered:

1 for each repetition

*** 59 BRIDGE TRANSFORM ***

FUNCTION

This instruction is used to aid in the conversion of a ratiometric Bridge measurement by obtaining the value for Rs which is equivalent to Rf[X/(1-X)], where X is the value derived by the standard CR10 Bridge Measurement Instructions (with appropriate multiplier and offset, Section 13.5) and Rf represents the MULTIPLIER value. The result of Instruction 59 is stored in the same location that X was.

PARAM.

DATA

 

 

NUMBER

TYPE

DESCRIPTION

 

01:

2

Repetitions

[REPS]

02:

4

Starting input location

 

 

& result destination [X]

03:

FP

Multiplier (Rf)

[MULT]

Input locations altered:

1 for each repetition

*** 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.

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