Industrial Network Solutions for Merrick Weighing Controllers

An increasing number of Merrick installations use industrial networks rather than relay contacts and analog signals. We see better performance, better accuracy and drastically better reliability. This is due to better on-line drill-down capabilities into feeder data, as well as the wide-spread use of trend recording. Other benefits include

• Highly integrated control solutions, allowing more innovative process control.

• Greatly reduced cabling cost - one network cable instead of a whole cable tray.

• Better resolution and accuracy for variable transfer - floating point numbers instead of 4-20 mA.

• More parameters and status bits can be added as needed.

• Better integrity - both sides will be aware of a network failure and can take action.

Newer Merrick MC³ and all Genetix controllers have built-in support for Allen-Bradley DF-1 Point-To-Point and Modicon Modbus ASCII and RTU. This allows for direct or converter based interfacing to almost all industrial networks. Data exchange between the controllers and the supervising system is done with table transfer. All applications use a Common Interface Table (CIT) for this purpose. The table has two components, Status and Control. The Status Table is transferred from the Merrick controller to the supervising system, and the Control Table goes the other way.

For configuration and troubleshooting see documents
Genetix GCM Configuration and Troubleshooting for DF-1
Genetix GCM Configuration ant Troubleshooting for Modbus
MC3 Configuration and Troubleshooting for DF-1
MC3 Configuration and Troubleshooting for Modbus

There are three classifications for network interfaces:

1. Fully Supported (FS), meaning that we have equipment on hand, such as PLC's and converters, to test any scenarium. Under some circumstances, we can directly provide customized solutions, such as network configuration files or PLC logic files.

2. Existing Installations (EI), meaning that at least one user is operating a network successfully, and we have the configuration information or, in some cases, contact information.

3. Conceivable Solutions (CS), where we can infer that a certain configuration should work.

There are three types of network layouts:

1. Pont to Point (PtP), one Merrick controller connected to one port.
2. MultiDrop (MDrop), Many Merrick controllers directly connected to one port.
3. Point to Point to interface, then Multidrop (PtPMD), one Mererick controller connected to one interface, interfaces in a bus configuration.

Older MC³ and MC² controllers all support a multi-drop serial protocol, called ScaleNet, allowing direct access to the controller databases. There are three Merrick products available that utilize ScaleNet:

1. WinMerik, a Windows application for transfer of entire MC³ databases between controllers and PC files, allows for monitoring, logging and DDE serving of up to 10 MC³ registers. If you already have it, download this updated models.ini file and copy it over your existing one, typically in C:\Program Files\WinMerik.
2. SuperBridge for Allen Bradley, a DOS based application that bridges between ScaleNet and Data Highway Plus or DF-1.
3. SuperBridge for Modicon, a DOS based application that bridges between ScaleNet and Modbus Plus.

Some other helpful links:

Genetix Firmware Application Overview.

MC³ Hardware Reference Manual.

MC³ Firmware Application Overview.

Anybus is a registered trademark of HMS Industrial Networks AB

DeviceNet™ and EtherNet/IP™ are trademarks of the Open DeviceNet Vendor Association.

ProfiBus^® is a registered trademark of PROFIBUS International.

MODBUS^® is a registered trademark of Schneider Electric.

PLC-5, SLC, ControlLogix and Allen-Bradley are trademarks of Rockwell Automation.

2011-06-22/Lars