Modbus Scaling - Emerson Micro Motion 3711 Configuration And Use Manual

Modbus Interface
Table 12-4 Modbus Registers parameters
Parameter Description
Function Select the Modbus function for which registers will be defined.
Function Name Specify the tag to be used to identify the Modbus function.
Starting Register Specify the first register to which a point will be mapped.
Ending Register Specify the last register to which a point will be mapped.
Device Use the Select TLP dialog box to specify the point to be
Parameters mapped to the Starting Register.
Indexing For register ranges that contain more than one point, specifies
how additional points are defined:
• Point: consecutive point logical numbers. The parameter
number remains the same.
• Parameter: consecutive parameter numbers. The point logical
number remains the same.
Conversion Specify the conversion code. The conversion code specifies the
datatype conversions to be applied to Modbus data in this
register range before it is sent to the host or written to the
Model 3711.
10. Click
12.5.1

Modbus scaling

Two types of scaling are provided: integer and float. You may define either or both.
• Integer scaling is applied only when Conversion Code is set to 1–8.
• Float scaling is applied only when Conversion Code is set to 17–24.
You may leave float scale values set to 0.0 if you will not use them.
Integer scaling
Analog inputs and outputs can have different endpoints and ranges. Integer scaling is used to
normalize I/O integer data so that the Modbus host does not have to retrieve scale information for all
analog inputs and outputs. Integer scaling can also be used to avoid negative values.
The values configured for integer scaling are applied to all analog data, AI Raw A/D Input (Type 3,
Parameter 17), and AO Raw D/A Output (Type 4, Parameter 9) registers.
The following equations show the relationship between the analog value and the scaled integer. In
these equations:
• AnalogHigh = upper end of analog data range (e.g., 20 mA)
• AnalogLow = lower end of analog data range (e.g., 4 mA)
• ScaleHigh = configured High Value for integer scaling (default = 4095)
• ScaleLow = configured Low Value for integer scaling (default = 0)
• AnalogValue = value of analog output
• ScaleValue = scaled integer value that corresponds to AnalogValue
140
or .
Apply OK
Comments
If more than one register is
specified (the Ending Register is
greater than the Starting Register),
all registers will be populated with
a set of point data. The Indexing
parameter controls how the set is
defined.
Default: 0 (no conversion)
Conversion codes are listed and
defined in Table 12-5
®
Micro Motion Model 3711 Gas Flow Computers
.