Displays can be damaged in adverse environmental conditions. Like most electronical devices their expected life span can be reduced by extreme temperatures, humidity or cleaning products, among others. Therefore it is important to choose a high-quality product and keep it in an adequate environment. Below we have listed environmental conditions that we should bear in mind when choosing, installing, using and maintaining our display.
Heat
Electronic devices in general react sensitively when facing temperatures that are too high. This can lead to the complete destruction of the electronic device, and displays are not an exemption. How displays react to heat depends on various factors. These are, for example, the materials used, the quality of components, the cooling system and the brightness of the background lighting.
Most displays for industrial use have a proper temperature range from -20° C to 70° C. Since they are built into a housing and emit waste heat themselves the maximum possible ambient temperature is lower, however. To dissipate the heat occuring in the housing a cooling system is needed. Cooling systems are divided into passive and active cooling systems. In passive systems the heat is dissipated via the housing or via ventilation slots. Cooling elements can be used as well, which enlarge the surface of the housing.
Among passive systems we find heat sinks, which are thermal conductor metals that conduct heat away from the source and dissipate it to the air, and heat spreaders which are metal plates sometimes placed between the heat source and the heat sink as a way to avoid heat concentration in a concrete point and finally heat pipes, sealed tubes filled with liquid connected with the heat source at one end and the heat sink at the other, the cooling power of this liquids is very high.
Sometimes using passive cooling systems is not enough to cool our systems. In this case we need to complement them with an active cooling system. The most widely known active cooling system is probably the fan, which is used to accelerate air flow in many electronic systems, since natural convection is not enough for most of them. However, among active cooling systems we also find liquid cooling systems, consisting in open- or closed-loop circuits where liquid is pumped. This systems are usually used in high performance electronics.
In a lift high ambient temperature does not only occur at southern latitude. In a glass lift exposed to direct sunlight temperatures above 60°C can easily occur as well.
Cold
Extremely low temperatures can also cause damage to displays. If the display is used in ambient temperatures of less than -20°C the scren liquid can freeze and components can become rigid and brittle or even burst.
A temperature fluctuating from minus to plus temperatures close to 0°C can be problematic as well. At this temperature surrounding moisture condensates, causing problems in all electronic circuits in the display.
In general LCDs react more sensitively to lower temperatures when compared to TFTs. In LCDs the screen build-up is significantly slower.
Humidity
Humidity is evaporated water contained in the air. There are two ways humidity can occur: absolute humidity, is the objective amount of water in the air in a concrete moment, and relative humidity is the percentage of absolute humidity compared to the possible maximum for a concrete temperature.
Both, very low and high humidity levels can destroy a display. In the first case, relative humidity levels under 35%, static electricity can occur, resulting in electrical discharges to the display and destruction of the whole system.
High relative humidity levels, over 80%, increase the risk of water condensation on the display components' surfaces, this leads to corrosion and, in extreme cases, to short circuits on the device. Destruction of the electronic systems can hardly be avoided.
Salty environment
Salt concentration increases the problems with and the effects of humidity. This means if condensation occurs in a display used close to the sea, for example on a ship, oxidation and corrosion will appear faster than in a non-salty environment. Short circuits are favoured by salt as well, since this element is a good electricity conductor.
Cleaning and sterility
A beautiful display should be perfectly clean at all times. Especially if the display is equipped with a touch sensor greasy fingers will occur very fast and will worsen the optical appearance. We are therefore always anxious to keep our display clean and usually use common cleaning agents. But many cleaning products can harm our display. Many cleaning agents contain acids, alcohol or corrosive liquids, which may attack the screen, the housing or internal components. In some monitors the display is protected by a plexiglas pane and sometimes the housing itself consists of synthetic materials. These materials react especially sensitive to chemical cleaning products. Before cleaning it is essential to read the information regarding the cleaning of monitors.
In some places sterility is especially important, such as in medical areas. Here the surfaces have to be sealed, and must not have holes or joints in which germs might accumulate and they have to be especially resistant to various chemical cleaning agents.
Vibration
Mechanical vibrations can influence the longevity of electronic devices as well. There are two types of transmission of vibrations. Airborne sound, which is transmitted via vibrating airflow, and mechanical vibrations, which are transmitted via the structure in which the display is placed.
Mechanical vibrations can destroy displays. Relevant here is the strength of the vibrations, the duration and the frequency. Through resonances the vibrations in a system can amplify. After some time this can lead to electronic components being shaken off and therefore to the destruction of the device.
If monitors are to be used aboard ships, where the main engine is constantly shaking, many measures are taken into account while designing the electronics, to counter mechanical stress. Additionally, the mounting of the monitors can occur 'swimming' in a dampening material that reduces the transmission of vibrations.
Sunlight exposure
If a display is exposed to immediate sunlight the display content is harder to recognize. The background lighting has to be significantly increased and additional measures, such as glass with anti-reflection coating, as well as optical bonding, should be used.
A monitor that is exposed to direct sunlight for a longer period of time this can also develop high temperatures in the housing. When the monitor is built into a glass lift the sunlight exposure can result in a high ambient temperature.
If a monitor with glass made of synthetic materials or a plexiglas pane is exposed to direct sunlight the synthetic materials can fade and become brittle.
Vandalism
Vandalism is the wilful destruction of property. This means, not only graffiti, breaking glass, wall or metal scratches, but also computer viruses have to be classified as vandalism.
Sensitive electronic devices, such as monitors, have to be particularly protected in public spaces. In monitors a special safety glass is used, which is mounted before the display to protect it. The mechanic of the monitor and the supporting housing has to be stable enough to absorb hard impacts.
To resist destruction by means of fire no plastics should be accessible.
Contamination as it may occur with graffiti has to be removed using strong chemical cleaning agents. The monitors should not be harmed by this either.
If electronic devices are directly connected to the internet, or if programs or files can be uploaded by the the users, various measures to protect the system are to be planned. This includes a firewall, encrypted data transmission and a rigorous rights management system, which save the electronics from manipulation.
EMC and noise emission
All electronic devices emit electro-magnetic signals and are influenced by electric or electro-magnetic disturbances. Electromagnetic compatibility (EMC) is the ideal state when electromagnetic fields, that are emitted by the devices, disturb neither other devices nor the device itself.
The requirements for a device to be sold in the EU are described in the normative guideline 2004/108/EG of the European Parlament and in various other norms and normative guidelines
(see Wikipedia). Summing up, the guideline defines a device to have a high degree of compatibility in order to avoid disturbances to other devices.
Electromagnetic disturbances can be prevented in the emitter or the receiver. When designing electronic components many things have to be considered that can reduce the emission of electro-magnetic signals and that make the devices less sensitive regarding influences from the outside. Further measures can occur in the design of the housing or running of the wires.
In displays poor EMC is easily recognizable by poor image quality. Especially capacitive touch sensors are very sensitive towards disturbing signals from the outside.
Among the main causes of electromagnetic disturbances are unconnected inductive loads, frequency inverters, as well as the now very common wireless transmitters, such as Wi-Fi antennas.
