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McQuay Micro Tech Open Protocol Driver Manual Page 17 of 35
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Appendix A. Advanced Topics
Appendix A.1. Scaling
User Scaling:
The user can specify scaling in the configuration file which allows a value to be scaled before being
stored in a Data Array or after being extracted from a data for writing to McQuay device. This scaling
is specified by using the following keywords in Map Descriptor definition.
Data_Array_Low_Scale,
Data_Array_High_Scale,
Device_Low_Scale,
Device_High_Scale…..
Device Scaling:
The raw values read from a McQuay device may be treated as raw values or they may be scaled.
Device scaling is the term used to describe the hard-coded scaling specified by McQuay for each
data field. By applying device scaling the user can avoid details or knowledge of the scaling and used
the converted value directly.
If this scaling is required then use the Device_Scaling parameter (see 4.4.2)
There are 5 device scaling methods. X refers to the raw value obtained from the McQuay device.
The method that will be applied to each field is shown in the following table.
Table 1 – Device Scaling Method applied to each Field
Method Id. Device Scaling Method
1 X
2 X / 10
3 ( X – 1000 ) / 10
4 X / 2
5 X - 100
6 ( X – 100 ) / 10
7 ( X / 5 ) + 20
8 ( X / 5 ) + 55
9 ( X / 5 )
10 ( X / 5 ) - 100
Note that when device scaling is applied it is applied without consideration of the raw value. Where
the raw value has a special meaning (available in the McQuay packet documents for the equipment
type of interest); this driver does not apply any special consideration to these special values.
As a Client: - Device and User scaling may be applied.
As a Server. Device Scaling and User scaling is not applied. The raw value written to any data
location is stored as is and the raw value read from a Data Array used in formatting the response to
a read.