HMI and SCADA
Questions and Answers
2. What is the HMI client?
The HMI client is VDS Viewer (Java application) that receives and displays data from HMI Server, which is the HMI client’s interface with Data Server. A special feature of the HMI client is that it is a thin client , meaning that no additional software is required for it to carry out the above function, significantly reducing the total cost of ownership. As a basic security feature, data access is limited depending on user privilege, and an optional operation shield package is available that restricts access via keyboard commands to critical system operations such as system shutdown. An additional feature of this package is the always-on foreground display of specified windows, turning the PC running this software into a dedicated HMI client PC.
3. What components does VDS consist of?
VDS is a Web-based HMI/SCADA application that consists of HMI Server/Data Server and an HMI client. The HMI Server/Data Server software has a simple three-layer hierarchical structure. In the bottom layer, an IO object transfers IO data to Data Server by means of a device-driver plug-in. In the second layer, Data Server runs as process management software, processing the data based on tags. VB applications run in this layer to access Data Server. In the top layer, HMI Server runs as message management software, serving as the HMI client's interface with Data Server.
4. How do devices link with VDS?
As options, drivers have been provided for linking with PLCs (currently, the Yokogawa FA-M3, Mitsubishi Electric MELSEC series, and Omron SYSMAC series), power monitors (Yokogawa M&C), data acquisition equipment and recorders (Yokogawa DARWIN and DAQSTATION), and temperature controllers (Yokogawa). For connecting the VDS with unsupported devices, drivers can be easily developed with a custom driver kit and installed.
5. How is the OPC function implemented with VDS?
VDS has a built-in OPC server function and an OPC client function for which an optional OPC Server Driver must be installed to make the I/O object act as an OPC client. By using these OPC functions, VDS can connect with other vendor's SCADA applications to acquire data by specifying tags, and it can exchange data with an upper-level system such as PIMS for production management and quality control.
6. What security functions are provided with VDS?
As a standard security function, users can be divided into groups for which operations such as control object access, running tools, etc. are restricted and user operations are logged. These users and groups are controlled under Window's user and group management, i.e. no special user management software is required. An optional Extended Security Package is available which adds operation record file protection and RunAs dialog box password protection to the standard security functions.