New options for the surveillance of working areas, production flow control, reactor monitoring or similar tasks are available in the form of modern network and video technology. This technology is also applicable for hazardous areas. The signals of one or more cameras can be integrated into process images at any operating station in a user-friendly way. It is also possible to remote control the video technology via the control system. This can be implemented with the aid of the ActiveX and OPC software interfaces.

Manufacturers that can provide a full range of components for such complete packages are still an exception. For a start, cameras that have an explosion-proof design and can also provide the required powerful functionality are thin on the ground. Secondly, only few video technology providers have the necessary expertise for the integration of video images and camera control functions into higher-level IT systems at a plant or company. But this is exactly the key component of mature solutions that are expected to cover safe and hazardous areas across a plant and provide maximum flexibility for surveillance tasks.

Video Surveillance Past and Present

The long-established standard in camera surveillance is the transfer of analog images in the form of a TV signal in CVS format (composite video signal), which today usually achieves the full resolution of the PAL or NTSC TV standard. This signal is generally used directly for full-screen viewing, for recording or for the display on a split-screen. However, conventional surveillance systems can usually only transfer an image to a few specific monitoring stations, which cannot be easily expanded. Network-based video technologies are more modern and more flexible in this regard. Either direct use is made of IP cameras, or the analog images of the CVS cameras are digitalized by means of video servers. Software is required to display or process the video images. For smaller configurations where no recording is required, R. Stahl has been offering the Smart Display tool. For more complex surveillance systems, larger CCTV projects can be implemented with the Probox 5/10/15 package or the Probox Enterprise Edition for any number of cameras. This software offers additional features, such as an integrated motion detector or the option of informing staff via email, text message or network protocols in case of an alarm independent of which software solution is being used.

onventional systems require the operating staff to keep an eye on a surveillance monitor located in the control room, in addition to other screens and displays. Having to watch such a separate screen can be quite impractical, particularly in cases where staff have to control cameras simultaneously, view their images, monitor processes and operate plant systems. Even more problems arise if the camera images can only be viewed on special monitors but would also be useful or even essential at other stations in the plant. This can only be remedied by CCTV systems that are fully integrated into the plant's control system. Their video signals are available at any human-machine interface (HMI) operating station and at the control station, and can easily be integrated into the process images on these screens. If required, the cameras can even be directly controlled from these stations.

Integration Via ActiveX and OPC

New solutions of this type can provide access via Ethernet to the digital video data from anywhere within the higher-level IT infrastructure. The pan, tilt and zoom functions of cameras can be more flexibly controlled via Ethernet connections than via the conventional serial connections. With regard to the software, images and controls can be integrated in various ways. As a rule, the integration of camera signals into a control system requires project-specific implementation by a programmer. Depending on which technical solution is chosen the requirements of the current visualization systems greatly vary. The most user-friendly solution by far for the integration of video signals has proven to be ActiveX controls, which is why R. Stahl has decided to make use of it. A camera view can be allocated to a process image window simply by dropping and briefly parameterizing a "drag & drop" object. However, as simple as the integration of images may be with the help of ActiveX, as complicated is the control of camera movements with this tool. Many control systems hinder or block the data transfer for such functions, and ensuring a reliable control function with this tool would be quite a complicated task. The more effective solution for these kinds of tasks is provided by the non-proprietary OPC interface (OLE for Process Control), which is based on the Microsoft COM and DCOM technologies for distributed applications. The great advantage of the OPC standard is that it is supported by all current automation systems and is implemented in these as a standardized I/O interface. Additionally, a range of ready-made, comfortable tools for control functions such as camera pans are available.

Three Camera Types

R. Stahl provides three camera types suitable for CCTV in plants with hazardous areas. All of them are of a mechanically robust design and achieve up to protection type IP68. Each series/model has its own specific features: The first model, the EC-730 autofocus camera, comes with an optical zoom providing up to 22x magnification. Added to that is the 11x digital zoom. The EC-730 is suitable for ambient temperatures ranging from -30 °C to +50 °C. Its seawater-proof aluminum housing protects the camera against aggressive salt air and spray. A full PTZ model (pan, tilt and zoom), the camera is mounted in a pivotable and revolvable position. Thanks to its zero-lux night vision mode the camera is suitable for round-the-clock surveillance, since it can capture and transfer useable images even in the darkest environments. Its 1/4"-CCD sensor provides a high-resolution image of 480 TV-lines.

The second model is the extremely compact, spherical EC-710-090 which, due to its 55 mm diameter fits into the smallest spaces. The optical system is protected by a chemically hardened lens. Even with the steel housing it weighs no more than 435 g and still resists ambient aggressive chemical substances as well as substantial mechanical stress, including vibrations. Its 1/3"-CCD sensor provides a high-resolution image of 470 TV-lines. The fixed camera viewing angle is +/- 90 ° horizontally and 68 ° vertically. Moreover, this camera can withstand extreme temperatures ranging from -30 °C to +75 °C, making it suitable for universal application in installations world-wide.

The third model is located under a transparent dome. This way, the EC-750 Ex-camera offers maximum flexibility, particularly for an all-round view. It also has a night vision mode, and a 18x zoom. The powerful EC-750 has a few additional features too: As an option, this camera type can be directly integrated into digital networks via its own IP interface. The intelligent model can furthermore follow up to 64 programmable positions and paths.

Conclusion

R. Stahl HMI Systems provides flexible complete solutions for the application of cameras in hazardous areas that can be integrated in plant control systems, supporting full integration of video images and functions for camera controls into current control systems. Such a complete package includes first of all the required hardware, ranging from cameras to all accessories such as cables, switches, terminal boxes, joysticks or keyboards. Secondly, users are provided with a powerful, ready-to-run software solution covering image integration via ActiveX and control system connection via OPC.