Campbell-scientific CR9000X Measurement and Control System Uživatelský manuál stáhnout pdf (Strana 173)

Section 5. Program Declarations

CONST

Declares symbolic constants for use in place of values.

Syntax

Const constantname = expression [, constantname = expression] . . .

Remarks

THE CONST STATEMENT HAS THESE PARTS:

Part Description

constantname Name of the constant.

expression Expression assigned to the constant. It can consist of literals

(such as 1.0), other constants, or any of the arithmetic or logical

operators.

Tip Constants can make your programs self-documenting and easier

to modify. Unlike variables, constants can't be inadvertently

changed while your program is running.

Caution Constants must be defined before referring to them.

Tip Use all uppercase letters for constant names to make them easy

to recognize in your program listings.

Const Declaration Example

The example uses Const to define the symbolic constant PI.

Const PI = 3.141592654 'Define constant.

CONSTTABLE/ENDCONSTTABLE

Used to declare one or more constants that can be changed using the

CR1000KD keyboard display. The program is then recompiled with the new

values.

Syntax

ConstTable

Const A = value

Const B = value

EndConstTable

Remarks

The ConstTable declaration should appear in the declarations section of the

program, prior to the start of the main program. The intent of this declaration is

to define one or more constants in the program that will be listed in a special

table in the datalogger, and which can be edited using the CR1000KD

Keyboard display, and the program recompiled to use the new values.

Recompiling the program in this manner will reset the data tables stored in the

datalogger’s CPU and may make the Data Tables stored on a card unusable (if

the Data Table Header is changed), so all data should be collected before

editing a value in the constant table.

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Campbell-scientific CR9000X Measurement and Control System Uživatelský manuál Strana 173