How is ProcessLink installed and set up on a PC?


Dokument-ID TE3851


Veröffentlichungsdatum 13.01.2022
How is ProcessLink installed and set up on a PC?
Installation guide and quick start for ProcessLink OPC server
The ProcessLink OPCDA Server is an OLE for Process Control (OPC) driver for Microsoft Windows® designed to easily connect Hach modbus devices to OPC clients. These clients can be SCADA (Supervisory Control and Data Acquisition) packages or any other application designed to connect to OPC servers. The Hach OPC Datalogger is included in the event a SCADA package is not available.

How Does OPC Work?

OLE for Process Control is a communication standard developed by the OPC Foundation®. OPC uses Microsoft COM technology to send Process Control messages between programs.
Fundamentally, OPC is comprised of two parts, servers and clients. Servers translate data from hardware devices and convert the data to a standard format called Tags. Each tag represents a piece of data such as a sensor reading, an alarm state, or a status value. The second part, clients, connect to servers and use the OPC tags to perform tasks Process Control tasks.
The OPC server communicates with the networked modbus devices, and translates the device data into OPC tags. The Hach DataLogger is an OPC client. It communicates with any OPC server, and logs data to simple text files. Multiple OPC Clients can access the same server at the same time. Virtually all 32-bit SCADA packages function as OPC Clients, allowing them to access data in a standard way.


To start using the ProcessLink OPCDA server, perform the following steps:
  1. Start the ProcessLink OPCDA server- click on the start button, select programs, Hach, ProcessLink, OPCDA Server.
  2. Discover devices- The OPC Server can discover known modbus modules attached to the device network. OPC tags are created and named automatically. This eliminates the tedious task of manually configuring Modbus registers.
    1. Click the Wizard button or select discover from the main menu.  A dialog window opens telling you to connect your device networks to the computer.
    2. Click the next button.  A new dialog window opens warning you that the Auto Discover process may take several minutes. This is because the wizard will check each selected COM port and IP address for known devices.
    3. Click the next button.   A third window opens which shows the progress and status of the Auto Discover wizard. As devices are found they are added to the device list. The status bar indicates how much of the entire process has been completed. Indicators at the top of the dialog show how many possible device configurations have been checked and how many devices have been found.
    4. Click the finish button.  Any discovered devices will be added to the configuration.  If a duplicate device is discovered you will be prompted to replace, skip or merge the devices. If you choose replace, the existing device will be replaced with the newly discovered device. If you choose skip, the discovered device is discarded. If you choose merge, the wizard will attempt to add the OPC tags from the newly discovered device to the existing device in the configuration.
  3. Check the device settings.
    1. Select a device from the left window pane.  Right click and choose properties.  Each field in the device properties is described below.
Name: A name that uniquely identifies the new device. This has repercussions on any OPC clients because the OPC clients will try to attach to an OPC tag using its name. If you change the name, any OPC Clients such as a SCADA may need to be updated to mirror these changes.
Address The modbus address of the device (1-247)
Poll Rate The rate that the OPC server queries the device for register data. Note that the OPC Server does not poll the device unless a client requests data, or polling is activated from the server. 
Word Swap Floating point numbers in modbus require two registers. The modbus specification does not indicate which order the registers should be in. Some devices will need the registers swapped to form the correct 4 byte floating point values. This should be unchecked for Hach devices.
Input Buffer Size The input buffer size specifies the size of the largest message the computer can send to it. This limits the number of registers that can be written to the device in a single message.
Output Buffer Size The output buffer size specifies the size of the largest response the device can send to the computer. This limits the number of registers that can be read in a single message
RTU/ASCII The OPC server will support both RTU and ASCII over the serial port. RTU is the default.
Version The embedded software version in the device.
Data from device Uses an actual device and the specified COM Port settings for tag values.
Simulate Tag values are simulated as a Sine, Ramp, or Random value. The simulated behavior of each tag can be set individually. If this data source is selected, data is not read from a device.
In Service This check box controls the device online/offline status. If the device is offline, all sensors attached to the device are considered offline because we cannot communicate with them. To control the online status of a specific sensor connected to the device, see the Sensor Group Settings page.
Load Profile This button activates a window that allows the user to load a specific device profile. Normally devices are discovered automatically using the modbus device id message. For devices that do not follow the standard Hach id format or when adding devices in simulation mode, the user should select the register map/profile for the desired device.
Reset Stats This button will reset the IO statistics for the device
Each field in the device communication properties is described below.
IP-UDP: This selection tells the device to communicate using modbus over IP. Currently UDP is the only protocol supported.
Serial Communications: Tells the device to use serial port communication.
Timeout (ms): The number of milliseconds to wait before sending message again.
Retry Cnt: The number of message retries before canceling message.
IP Address The address used when IP communications is selected.
Port: The serial port to communicate with device.
Baud: The baud rate to use for device communications. Standard/Default for Hach devices is 19200.
Stop Bits: The number of stop bits. Modbus standard is 2 stop bits. The Hach standard/default is 1 stop bit.
Parity: Parity bits. Default is None.
Data Bits: Default is 8 for RTU mode.
Manually Adding a Device:
To manual add a device; stop the polling, select add/device.
Upon selecting Device, the device search window will activate which allows you to search for a single device at a specific address and serial port. Click the Search button to query the port and address for a device id response. Click OK to add a device without searching. Click Cancel to quit without adding a device. Once a device has been added, the device configuration window will activate allowing the user to customize the device settings.
Polling a Device:
To start polling on a specific device, select the device in the left window pane, then select the menu item Poll | Start Polling. When polling is active on a device, the menu item will be checked.
To stop the device polling that was activated from the OPC Server user interface, select the device in the left window and then select the menu item Poll | Stop Polling.

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