Campbell-scientific LoggerNet Datalogger Support Software Instrukcja Użytkownika Pobierz pdf (Strona 181)

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Section 5. Real-Time Tools

StartRelativeToNewest(nsecPerDay,ordercollected);

MaxRunOverTime(“Server:CR1000.QtrHour.Temp”,Timestamp(“Server:

CR1000.QtrHour.Temp”),nsecPerDay)

would begin displaying a 24 hour maximum immediately, provided that the

data is available in the communications server’s data cache.

Aliases

If a data value is used multiple times in an expression, the expression can be

simplified by declaring an alias for the data value at the first of the expression,

in the form:

Alias(alias_name, data_value)

For example,

StartAtOffsetFromNewest(5,OrderCollected);IIF(ABS((“Server:CR1000.MyT

able.Value”-

ValueAtTime(“Server:CR1000.MyTable.Value”,TimeStamp(“Server:CR1000.

MyTable.Value”),30*nsecPerSec,0))>10 AND

ABS(ValueAtTime(“Server:CR1000.MyTable.Value”,TimeStamp(“Server:CR

1000.MyTable.Value”),30*nsecPerSec,0)-

ValueAtTime(“Server:CR1000.MyTable.Value”,TimeStamp(“Server:CR1000.

MyTable.Value”),60*nsecPerSec,0)))>10,1,0)

can be replaced by:

Alias(X,”Server:CR1000.MyTable.Value”);StartAtOffsetFromNewest(5,Order

Collected);IIF((ABS(X-ValueAtTime(X,TimeStamp(X),30*nsecPerSec,0))>10

AND ABS(ValueAtTime(X,TimeStamp(X),30*nsecPerSec,0)-

ValueAtTime(X,TimeStamp(X),60*nsecPerSec,0)))>10,1,0)

Synchronizing Variables

The ValueSynch function can be used to synchronize data values coming from

multiple data sources so that you can display the results of a calculation on

those data values in a single component. The Value Synch function takes the

form:

ValueSynch(synchronized_name, data_value)

Where synchronized_name is the name of a new variable that will be used in a

calculation at the end of the expression and data_value is the name used within

RTMC to access the data value, i.e., Source:datalogger.table.variable.

For example, if you wish to display the average air temperature of two stations

on a chart, the following expression can be used to synchronize the timestamps

of the stations and then calculate the average air temperature:

ValueSynch(air_temp_1,”Server:CR1000_1.SECOND.air_temp”);ValueSynch

(air_temp_2,”Server:CR1000_2.SECOND.air_temp”); (air_temp_1 +

air_temp_2) / 2

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