Campbell Scientific LoggerNet Datalogger Support Software - Manual (Page 181)

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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