What is a video- or monitor wall?

What is a video or monitor wall in control rooms?

A video- or monitor wall consists of a matrix of displays, which are built up to one large display wall. These displays are in general DLP rear-projection cubes, available from 50”-100” in XGA, SXGA, SXGA+ or HD resolution. One of the main advantages of these displays that they don’t suffer of burn-in or image retention when displaying static pictures.
State-of-the-art DLP cbes have features like automatic brightness and colour correction, automatic double lamp systems.
Another type of display available for video walls are Plasma displays, but these are rarely used in control rooms, because of the burn-in of static pictures and because of the big gap between the individual displays. The third technology used in control rooms are LCD TFT monitors. As standard large format LCD monitors have a big bezel, nowadays professional systems for 24/7 are available with narrow bezels. The disadvantage of this technology is the memory effect (also called image retention) when displaying static pictures over a long period. There are several ways that this phenomenon can be avoided professional manufacturers have features and ways how to do that. Standard LCD monitors are not designed for control rooms, but professional control room equipment manufacturers have designed systems with optimizing features for 24/7 operation.

Display possibilities on large screen systems:

-SCADA and DCS systems
-maps, grids, networks (e.g. power grids, pipelines,
roads, rail network…)
-video sources (CCTV cameras, IP cameras, DVD, VCR….)
-servers or workstations
-production processes
-presentations
-timetables
-surveillance systems
-alarms
-flow diagrams
-status messages
-….

DLP cubes

Operation time of these systems are > 100.000 h. Experienced manufacturers offer minimum 10 years spare parts availability. The only real disadvantage of these systems is that they require more space than flat panel displays, but in terms of operation and maintenance costs, as well as for 24/7 ability these systems are the most used in control rooms nowadays.
A cube in general consists of a cube chassis (metal housing), a two element optical effective front screen, a 45° mirror, a projection engine, a input box and a back panel.

The front screen:
Double element optical effective screens. Professional systems have these screens pre-mounted on a screen frame which can be easily mounted on the cube chassis.


The cube chassis:
Some manufacturers deliver the chassis as kit to be mounted on site. The disadvantages are, that more time is required for the installation, as well as these systems are mechanically not so stable. Specialized manufacturers deliver the cube chassis pre-mounted and these are very stable and robust (possibility to install and dismount the systems several times). Also the engines and the 45° mirrors should be pre-mounted.

The engine:
This is the hart of each rear-projection cube in general with DLP technology from Texas Instruments. The engine consists of an optical unit, formatter board and other electronic boards, power supplies, fans, autom. Brightness and colour sensor, DLP chip, colour wheel and lamp units. Attached to the engine you will find the input box with lamp drivers, power supplies, fans, input boards and scaler board.
In general such a rear-projection cube comes with one DVI and RS-232 input. Optional inputs should be available and could be additional DVI or RGB inputs, video inputs, LAN input, optical fibre input.
The scaler board is in general required, when no external controller is used and one signal should be displayed over several cubes.


The basement:
The lower row of a cube wall consist of a matrix of rear-projection cubes, which need to be mount on a basement. In general this is of solid steel. The height has to be defined when ordering such systems. The basement should also have adjustable feet. The height depends strongly on height of consoles, workstation monitors, operator positions etc. Optionally also rail systems or shock absorbing basements should be available.


Height of basement
Please take care that the upper edge of monitors on the operator desks are quite low. The standard height of a basement of a videowall is 100 - 120 cm. This strongly depends from the ceiling height. So for the height of a basement of a videowall, you should take into consideration the ceiling height, height of operator desks, height of monitors on operator desks.

Viewing distances to a videowall
Good readability of fonts = max. 250 cmLimited readability of fonts = 450 - 500 cmNo readability of fonts, but graphics and diagrams could be seen = 650 - 700 cm
Space requirements:
Large screen walls consisting of DLP cubes, need normally minimum 50 cm in the back of the displays for service and maintenance. Otherwise rail-systems or front-access system have to be used.

Front access difficulty:
Large screen systems that have a backward accessibility for service and maintenance have fixed screens and therefore a maximal gap of 0.68-0.8 mm between the individual modules (this gap is necessary to allow for temperature-caused variations of the materials).
Front maintenance requires movable screens. This movability of the screens is only
possible with wider gaps between the cubes. The width of the gap between two
front-maintenance cubes is up to 2 mm, so we cannot talk of a “seamless” video wall
anymore. In general, large screen systems have the following characteristical attributes:
∙ Mullion: 0.3 mm per screen, this leads to a gap between two adjacent screens of
about 0.68 mm.
∙ The distance from pixel to pixel can be up to 1 mm with conventional back maintenance-access.
∙ This gap can be up to 2 mm with front-maintenance cubes (pixel to pixel).

Mechanical Reliability (Limitations):
Since the screen frame has to be moved for service and maintenance works, it must
be granted that its construction and installation is done is very stable and accurate.
Repeated opening and closing of a low-quality construction will lead to misadjustments of the screens which will result in a loss of sharpness for the entire video wall. Already variations in distance of only a few decimillimetres can affect the sharpness of the entire system.

Maintenance (Exceptions with front-maintenance access):
The service staff has to stand in front of the video wall to do their work. This means
they have to stand right in view of the people who are watching the video wall, so the
operation of the entire wall is disturbed for a while. Video walls with back-access for
service works can be repaired while the wall is in normal operation except for the cube that gets repaired.

Disadvantages front access:
- Wider gap between the cubes, up to 2 mm instead of 0.68 mm with conventional cubes.
- Difficult to service in operation, service staff disturbs the view on the video wall.
- Danger of damages and scratches that may happen to the screens of larger video walls, if
the screens are not handled with adequate care.
- Servicing larger walls may require the use a scaffolding or an elevating platform, which leads to higher costs.


LCD monitors

Operation time 50.000 h
Nowadays this upcoming technology is also used more and more in control rooms. Professional systems manufacturers offer LCD systems optimized for 24/7 operation with narrow bezels from 40”-46” in 1366x768 pixels and 52” 1920x1080 pixels.
These displays consist of a LCD panel, mechanical frame, electronics, fans and inputs and scaler boards.


These systems can be either wall-mounted or mounted on a display rack with feet.

Display possibilities

The display possibilities with cubes or LCD screens are in principle similar.

Monitor imaging

There the source (e.g. a PC) is connected directly to the displays. Than the large screen display is used as a stupid large monitor.

Using internal scaler

Here the signal is connected to one display (all other displays in the videowall are connected via loop-through) via the internal scaler the signal is distributed to all the displays that the image appears as one big image over the complete video wall. With sophisticated solutions you will additionally be able to make a PictureInPicture (PIP), means you insert an additional image on the displays.

External graphics controller


Modern control room systems use external graphics controller in order being more flexible in the number of sources and the management of the system. With such a controller a lot of different sources can be connected and displayed at the same time on the large screen wall:

-DVI or RGB
-analog video or IP video
-Applications running directly on the controller
-LAN capture sources

Professional solutions display all these sources in real-time.

All these sources normally should be freely positionable and scalable on the large screen wall. Professional systems also have a so-called wallmanagement software available, with this all connected displays, processes and sources can be managed easily and events can be launched on the wall etc..

This controller should in general be located in a separate server room, in that case please be careful with the cable length, if distance is longer than 7 m optical fibre cables has to be used as connection between cubes/LCDs and controller.

Installation conditions of a large screen system
The installation site must be dust free. All dust generating works must be finished.
The height of the basements (height image bottom) must be defined with the order, at latest 4 weeks before delivery.
If the videowall shall be installed in a curved arrangement, this must be clarified with the order or at latest 4 weeks before delivery. Power cables, network cables and all source cables must be finished, be accessible and pluggable at the position of the large screen.

All cable ways must be known and be accessible.
At the end of the installation, the passing of risk is made in written form, to transfer the responsibilities of any occuring later damage of the system. The acceptance through the customer together with all technical details related to the large screen system and the site must be clear and discussed at the latest 4 weeks before the installation. Also it must be clarified how many engineers you need from eyevis and if some staff is available on site.

Operation
General Operating Conditions
Storing: 0 – 50 °C, up to 3500m over NN
Operation: 18 - 25 °C recommended, 0-3000m over NN
Humidity 20 - 80% not condensed

Please check necessity of an air condition !

Sizes
Distance LVS rear side to site wall:
· min. 50 cm at not movable installations for cubes
min. 5 cm with LCD screens
· min. 10cm at movable installations (rail system/front access) for cubes, on request for LCD
screens.
Distance LVS upper side to site min. 10cm


Divers
This specification is part of the order acknowledgement for the below mentioned project. These specifications have to be fulfilled before the installation can be made.
For a perfect installation and setup of a large screen system certain points have to be fulfilled.

All construction works at the installation site have to be completed before the
installation of the video wall.

The site, where the video wall will be located must have a climate controlled environment. The required dust class must be 100000 or better (100000 particles of 0.5 μm or larger per cubic feet).

Dimensions of doors at site must have appropriate size.

If the system must be transported more than one floor without elevator, the customer has to provide two people helping to transport the equipment.

Providing lifts, risers or other special equipment is not part of our standard deliveries. Prices can be obtained from the Eyevis sales department.

Adaption of applications and integration of customer’s systems is not part of Eyevis installation work, if not agreed in written form with the PO for the system/installation.

Cable moving, connection of power cables, external cabling for the transmission of video, RGB/DVI or other signals as well as network cables is not part of the Eyevis installation work, if not agreed in written form with the PO.

The site must have sufficient service are behind the video wall, if no frontal maintenance or rail-system is part of this equipment.

The installation surface must have a sufficient level and sufficient load bearing capacity and should not bend or sag under the load of an Eyevis system by more than 1 mm. The possible floor surface should be concrete, wood and false floors or platforms. The floor surface must provide enough resistance in lateral movements that in light shaking movements the system will not move.

If panelling or covers around the video wall is wished, it should be installed after the complete installation of the video wall. It is not permitted that the covering touches the screens, so sufficient space between screens and cover must be respected (or foam, soft rubbers or bristles have to be used).

Grounding must be available at installation site.

When the installation will be made after the equipment is already delivered, the equipment has to be stored in appropriate conditions (dust-free, temperature- and humidity conditions).0-50° C, max. 60% rel. humidity

Please note that it could be possible that screens have a bow during and just after finishing the installation. Screens need at least 2-3 weeks on site until to acclimate to the changed humidity and temperature conditions (for cubes only).

If temperature and/or humidity conditions vary from the Eyevis recommendations, the
Project manager has to be contacted about that. He will decide if the system can be
installed with these conditions.


Transportation/storing/unpacking

Use of proper transportation ways and professional transportation companies.

Store the equipment in adequate storing areas and under adequate storing conditions.

Let the systems be unpacked only by experienced or appointed staff. Others might not be aware how to take care of it.

Always respect the instructions given on the packaging of the goods, never transport the goods in other positions than stated on the packaging.

There is no warranty for improper handling of the systems!


Screen handling (only cubes)

Always use the dimple gloves supplied when handling the screens.

Don’t lay the screens on critical surfaces (hot, dusty, dirty, ..).

Don’t scratch the screens with anything.

Handle screens with greatest care, as they are extremely fragile especially the 84” and 100” screens.

Memory effect/image retention (only for LCD monitors)


Please read carefully the instructions about the memory effect or image
retention. Instructions on request.

Memory effect or image retention is not under warranty.

Maintenance

For both systems, video walls consisting of a matrix of DLP cubes or LCD screens together with a graphics controller and a wallmanagement software, the most common maintenance action is cleaning the systems from dust and make some necessary re-adjustments. For DLP cubes another service action is to change a broken lamps, but as for most systems this is quite an easy task, it can be done by the operators.

Operation costs

DLP Cubes
In principle within the cubes you have to replace from time to time lamps (MTBF of around 10.000 h). After a certain time e.g. 35.000 h, it might be necessary to change the colour wheels of the system. The power consumption of these display units is very low.

LCD monitors
This is a quite young technology, in principle the LCD panels have a MTBF of 50.000 h, so it might be possible to exchange them when reaching this time, may be before if they have an image retention or memory effect. This task can’t be done by the operators, it has to be done by experienced service personnel in the factory. The power consumption of LCD screens is higher than with DLP cubes.

Which solution to choose?

In principle this strongly depends on the application, location and duration of use:

-available budget
-available space
-duration of displaying
-number of operators
-number and type of sources
-quality and resolution of sources
-displaying fonts, video or graphics
-viewing distance
-accessibility of site (big displays might not pass existing doors or aisles)
-environmental conditions (dust, humidity, temperature)
-lighting conditions (artificial and sun light)
-floors (computer or concrete floors
-wall constructions (if LCD monitors shall be hanged up)
-curved or plane arrangement of monitors/displays
-distance controller to displays
-expandability for future upgrades
-level of redundancy
-….

Which are the requirements?

-no direct light or sun one the displays
-not too long cable ways for copper cables, otherwise optical fibre has to be used
-stable temperature and humidity conditions
-as less dust as possible (otherwise special housings have to be used)
-no vibrations (otherwise special antivibration systems have to be used)
-good quality of sources (the best display can only be as good as the sources to
be displayed)
-quality of components
-trained operators, for operation and maintenance (e.g. lamp change)

As such a display wall is always only a part of the control room, there should be a good collaboration with the different parties like control room designer, console manufacturer and integrator in order to deliver a good solution.