Vaisala PTB210 SERIES Manuel d'instructions télécharger pdf (Page 50)

4.5.2 Expressions

Expressions are used as operators or numbers that produce a value or a result. The

programming of the automatic weather station requires such expressions in terms

of converting strings into numeric values as well as to save a squared sum over the

scan interval.

String Expressions

CRBASIC allows the addidtion and concatenation of string variables to variables of

all types using + operators. The serial output of the digitlal pressure sensor PTB210

is picked up as string which inevitably leads to problems having calculations with

it.

AirPressString = AirPress(1) + "," + AirPress(2)

SplitStr(AirPressNum(1),AirPressString,",",2,0)

AirPressString is an array of two serial pressure readings which is splited into two

equal numeric values assigned to the variables AirPressNum(1) and AirPressNum(2).

From now on every kind of mathematical instruction can be executed.

Mathematical and Logical Expressions

Mahtematical operations are written out as if they are algebraically. For example

the calculation of the squared value of pressure readings looks like following:

AirPress_SQ_1 = AirPressNum(1) * AirPressNum(1)

AirPress_SQ_2 = AirPressNum(2) * AirPressNum(2)

The squared sum is deﬁned in the data tables with the following expression:

Totalize(1,AirPress_SQ_1,IEEE4,False)

Totalize(1,AirPress_SQ_2,IEEE4,False)

This progression is applied to every reading.

A simple logical expression in the form of a counter for measured data perinterval

was already given in section 4.5 on page 46.

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Vaisala PTB210 SERIES Manuel d'instructions Page 50