Upgrading a Mark II to a Mark III

Reference, Installation, and Operations Manual

June 2013

3-9000-743 Rev S

 

 

C.3

Modbus Communication

C.3.1

Protocols

 

The Mark III meter supports ASCII and RTU Modbus communication. For ASCII Modbus, both

 

7E1 and 7O1 are supported. For RTU Modbus, 8N1 is supported. The communication ports

 

provide automatic protocol detection - only the baud rate and Modbus ID need to be specified.

 

Refer to Section 5.1 for details on configuring the meter communication parameters.

C.3.2

Registers

 

The Mark III uses a database for managing its information in which each piece of information is

 

stored in a database point. The meter utilizes a mapping file for cross-referencing database

 

points with Modbus registers for Modbus data access. Refer to Section 6.4 for further details.

 

The Mark III maintains backward compatibility to Mark II Modbus registers whenever possible.

 

The UnitsSystem register selects the units for Modbus communications. Available options are

 

U.S. Customary and Metric. These are the units in which the software Field Setup Wizard

 

displays properties. These are also the units with which the meter reports all of its rates and

 

volumes using Modbus communications. The selected units system applies only to registers

 

above 10000 and in the 2000-8999 range, other registers below 10000 are read in metric units

 

only to maintain Mark II compatibility. US customary units is the default setting.

 

For Modbus access information for a particular data point, consult

 

Daniel MeterLink online help. (There is a help topic for each data point. From Daniel MeterLink,

 

click on Help, click on Mark III Registers Reference, select the Index tab, start typing the data

 

point name until the desired point is highlighted, and then click the Display button.)

 

The Modbus map is available in Microsoft Excel format (MARK III Modbus Table.xls) on the Daniel

 

MeterLink CD and the Daniel website http://www2.emersonprocess.com/en-US/brands/daniel/

 

Flow/ultrasonics/Pages/Ultrasonic.aspx). Note that on the website, the file name may include

 

the file size (MARK III Modbus Table 386KB.xls).

 

The Daniel MeterLink program includes a means of converting a Mark II meter configuration to a

 

Mark III meter configuration for use in upgrading electronics heads. This feature is discussed in

 

Section C.4 below.

C.3.3

Log Access

 

Due to the Mark III meter’s enhanced log retrieval methods, accessing log records via Modbus

 

communication is not supported. All log records (daily, hourly, audit, alarm, and system) are

 

optionally accessible via Daniel MeterLink (see Section 6.6.6).

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Modbus Communication