Specifications

Main Properties
PlantScape Server and Client Configuration Guide 127
Engineering Units
In defining the PV of an analog point, you need to specify the engineering units
used in representing the PV value; for example, degrees Kelvin, ohms,
megalitres/minute, and so on.
Range High Value and Range Low Value
You also need to specify the highest and the lowest valid values of the range for
this point. For example, if the maximum temperature reading for an oven is 600
degrees celsius, and the minimum is zero, you need to enter the value 600 as the
Range High Value and 0 as the Range Low Value field so that the server can
correctly “scale” or convert the raw data captured from the controller.
Drift Deadband
In defining the parameters of an analog point you can specify “drift deadbands”
to eliminate unnecessary point processing and therefore reduce system load.
Whenever a value is scanned from a controller point, processing will only be
performed if the value has changed by more than the configured drift deadband
amount since processing last occurred. Only what you define as significant
change will be processed. The deadband value is expressed as a percentage of
the point range.
Point processing includes:
• Processing point alarms
• Processing point algorithms
Figure 8.5, “How Drift Deadbands Work” on page 128 shows how drift
deadbands work in relation to PV.
plscpcg.book Page 127 Monday, May 28, 2001 10:11 AM