Campbell Scientific CR6 CR6 Measurement and Control System - Page 166

Section 7. Installation 1. Evaluate an expression, take one path or action if the expression is true (= -1), and / or another path or action if the expression is false (= 0). 2. Evaluate multiple expressions linked with AND or OR. 3. Evaluate multiple AND or OR links. The following commands and logical operators are used to construct logical expressions. CRBasic example Logical Expression Examples (p. 166) demonstrate some logical expressions. • IF • AND • OR • NOT • XOR • IMP • IIF Table 29. Logical Expression Examples If X >= 5 then Y = 0 Sets the variable Y to 0 if the expression "X >= 5" is true, i.e. if X is greater than or equal to 5. The CR6 evaluates the expression (X >= 5) and registers in system memory a -1 if the expression is true, or a 0 if the expression is false. If X >= 5 OR Z = 2 then Y = 0 Sets Y = 0 if either X >= 5 or Z = 2 is true. If X >= 5 AND Z = 2 then Y = 0 Sets Y = 0 only if both X >= 5 and Z = 2 are true. If 6 then Y = 0. If 6 is true since 6 (a non-zero number) is returned, so Y is set to 0 every time the statement is executed. If 0 then Y = 0. If 0 is false since 0 is returned, so Y will never be set to 0 by this statement. Z = (X > Y). Z equals -1 if X > Y, or Z will equal 0 if X