ANPR cameras are a niche market within the CCTV market. They are a niche because they demand a number of additional functions over and above anything that mainstream CCTV cameras can provide.
If you are thinking of buying ANPR cameras, there are a number of vital pieces of information that you should consider and ask your potential supplier for information about the product they are offering you.
View General FAQ’s View Technical FAQ’sANPR cameras have the potential to suffer from water and water vapour ingress more than other forms of CCTV camera and need to be treated differently in their construction. MAV believe that the only way to ensure your system is built to last 5+ years of 24/7 service is to hermetically seal the camera to IP68. What does that really mean and why?
Rapier cameras are hermetically sealed. This means that we allow no physical access to the internal electronics and optics and instead use highly advanced techniques of settings and physical control (e.g. motorised zoom, focus and iris) to achieve perfect ANPR settings quickly and repeatedly. Not only that, we purge our cameras to expel the moisture within them at the time of manufacture and can thereby warrant that they will not suffer water/moisture ingress issues.
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For fixed cameras it is to stop the ingress of moisture which will condense inside the camera on the electronics and inside of the lenses and would lead to poor images and equipment failure. For mobile cameras it is additionally to combat driving rain/spray and the inevitable car-wash scenarios.
No. If you allow the air around us to enter a camera, you allow water to enter in the form of water vapour. This is similar to what we see when the air in a blue sky forms clouds and then drops as rain - the only thing that has altered is the air pressure and temperature. Unless a camera can operate in 100% relative humidity (%RH) (even the UK reaches 90-95%RH in the summer) then it is a damp squib waiting to disappoint. Any ANPR camera that specifies a working relative humidity less than 100% is not really offering one that is fit for purpose. MAV Rapier cameras are IP68 and work to 100% relative humidity (100%RH).
No, IP67 only means that water droplets will not enter the camera BUT it does not mean that water vapour cannot enter. Indeed, many IP67 enclosures have ‘breather’ vents that allow air to enter and leave the enclosure so as to allow pressure equalisation. The classic example of this is provided by GORE™ which has been utilised in clothing and industrial situations to stop water entering an enclosure but allowing air to move in and out. For clothing, this prevents rain from penetrating the outer skin but has the added benefit of allowing moisture (body heat/perspiration) to vent out - so reducing humidity within. However, the moisture transfer and water protection is not a one-way process - the GORE™ material both prevents water and allows air to move in BOTH directions. This feature is the killer for ANPR cameras because this ventilation method simply acts as a slow buildup of moisture, which can turn into condensation, which pools water and eventually leads to equipment failure.
The points at which air flows in/out of an unsealed or ‘vented’ camera can be as regular as daily when there are temperature changes between day and night that lead to air pressure changes. A more dramatic version will also happen during air transit where the pressure drops in the cargo hold and can actually inject high moisture content air (cloud) during landing.
MAV 100% test every camera to prove that it has no leaks on the seals between metalwork and glass by conducting a pressure test on every Rapier camera we manufacture. There is no way of knowing if your product leaks unless you do this test. If you don’t leak air, you won’t allow either moisture or water to enter. Manufacturers who allow air to enter by using breather vents or pressure equalisation techniques generally do not test their cameras for leaks - if they did then they would probably purge at the same time. So, if you buy a camera with a breather on it, there is no way that you or the manufacturer can say whether the unit is actually sealed from ingress of rainwater which is a poor situation.
Not without some additional facts being known. Nitrogen purging has entered common usage but has no real meaning without supporting facts. At worse, Nitrogen purging is simply a process whereby dry Nitrogen gas is blasted at pressure into an enclosure in the hope that it expels moist air (which, by the way, is already 78% Nitrogen). If you purge in this way, you generally need a point of entry for dry air and exit for expelled air - if you don’t all you are doing is putting the existing moisture under pressure with dry Nitrogen. If you do allow the injected gas to escape, you are simply wafting the gas through and hoping no pockets of moisture remain.
At MAV, we believe that the only way to warrant our camera’s fitness for purpose is to perform a purging cycle on the cameras. This means that EVERY Rapier camera is put onto a machine that injects dry air, sucks out the moist air in a breathing cycle that is continued for around 10-12 hours per camera. Every time the air is sucked out, the moisture content is measured and, only when the air inside has enough moisture removed do we consider it to be fit for purpose. Not only does this remove moisture from the air but also from every hydroscopic (water retaining) part within the camera e.g. PCBs for added protection.
The recognised standard is to measure the ‘Dew Point’ of the air within an enclosure. The Dew Point is the temperature at which the air will release the moisture it contains and lead to condensation forming. All Rapier cameras are purged to a level of -30°C (-22°F) or lower as their internal air Dew Point.
This means that unless the temperature of any surface within the camera drops below the dew point level then there will be no condensation on the camera lenses or circuitry. This does not mean that the ambient temperature cannot drop below this temperature since, within the Rapier, the heat from the camera modules and illumination will raise the internal temperature above ambient. In practice, MAV can take the dew point within Rapier cameras as low as -40°C (-40°F) just by continuing the same purge process for longer and have done so for customers operating in extremes of low temperature.
The Rapier cameras are fitted with motorised zoom, focus and iris controllable lenses. This allows the settings of the distance for accurate plate reading to be optimised without the need to open the camera’s enclosure to access a varifocal lens. Not only does this mean that all the environmental protection described above is preserved, it also means that cameras can be trimmed to the exact situation at any time using the camera’s control protocol.
View AllHide AllNo. A varifocal lens requires the installer to be able to make small adjustments to focus and zoom when the camera is in situ by moving the lens assembly by hand. This can mean that the installer has to take the camera apart to expose the varifocal lens and then adjust the available trims whilst up a ladder, in a cherry picker, on a gantry whilst also looking at a live image or ANPR capture. It is inappropriate to open cameras on site, against good engineering practice and would contravene health and safety assessments unless multiple staff are onsite. More to the point, it is not required since motorised zoom cameras allow all adjustments, especially the vital fine adjustments to be made safely in controlled conditions without exposing the camera’s internal electronics.
Yes. There are a host of features that a motorised lens will permit that have real and valuable benefit to any ANPR camera user. Nearly every Rapier 30/50 user has commented that the software controlled setup of the camera has lowered their cost of installation and is now capable of being done by staff with minimal training required.
The Rapier 30 and 50 cameras have both been calibrated to permit real-life settings to be deployed within seconds. Not only can the camera be zoomed to exactly the right field of view for the target distance but, more importantly, the focus at that point can also be set without the need to actually have objects in view. This needs to be thought about to fully understand just how valuable this can be. Imagine you are setting up an ANPR camera on a busy lane of traffic. Focussing on moving traffic is hard, you can’t stop the traffic or have a colleague stand in the road with a license plate, so what do you do? With Rapier 30 or Rapier 50 you just tell the setup software the distance you want to operate at and it will immediately go to the correct zoom level and focal plane - job done!
When a camera needs to be substituted due to damage or for redeployment, the original settings can be uploaded into the substitute camera and immediately take on the exact equivalent purpose.
The motorised lens has over 2000 selectable zoom positions between the wide angle and telephoto. By contrast, a fixed lens is normally only available in large jumps of field of view, e.g. 25mm, 16mm, 12mm.
Whereas fixed lens cameras can offer a purged environment because they require no installer changes they have the disadvantage of being fixed as the name implies. Therefore, on any normal site where multiple target distances exist, only zoom or varifocal cameras allow substitution - and only motorised zoom ones offer the ability to quickly substitute from preset memories.
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