Thermal cameras are finding their way onto many different mobile platforms these days. The technology is now small and light enough to be carried by some multi-rotor drone aircraft.
Drones come in many forms and with differing capabilities. Some are rated for water landings and can survive submersion ! Such water resistance is important for drone operators who will be operating over water as a motor failure will often lead to a dunking. Sh*t happens !
Now if the drone flying platform can survive a water landing, you really need any accessory attached to the drone to be similarly rated. Well you might expect such but that does not mean it is the case. Water immersion survivability is an enhancement not found on all drones or their accessories. You do not fly a non water resistant drone over water, simple. That is unless you are happy to lose it if a motor of system fails.
OK to the thermal camera that is the topic of this post......
FLIR produce their VUE and VUE Pro series of thermal imaging cameras that may be mounted on remote controlled aerial platforms. The VUE cameras are really just a variant of the TAU 2 core. The TAU and TAU 2 are found inside many thermal cameras but they are protected from the elements by the outer casing that encloses them. In the case of the FLIR VUE, there is no additional water proof casing to protect the bare core chassis. FLIR have elected to not protect the core from water with a case, but rather to use silicone sealant in an attempt to add water tolerance to the chassis. Such a measure is relatively effective against dust and water spray/rain. It does not, however, enable the camera to be submersed in water for any significant length of time. Water will likely find its way in somewhere over time, especially if the camera is submerged at a decent depth where pressure on the casing forces water past seals or sealant.
So is the FLIR VUE adequately sealed for use on remote controlled aerial platform ? Well that all depends on where the camera is located and where the aircraft will be flown. If the camera is protected inside a protective housing, it gains protection from expected threats and the vulnerabilities to damage may be reduced to acceptable levels. If the camera is just mounted 'naked' under an aircraft, it is vulnerable to many threats, including impact, dirt, rain and even full submersion in water. If the aircraft is not going to be flown over water, the risk of submersion in such is removed.
Can the FLIR VUE survive full submersion in water ? Well from what I can see in the attached images, I suspect that the answer is a definite no. It will drown !
The story of this unfortunate FLIR VUE camera is not that unusual.
The camera was mounted on the underside of a Quadcopter that was being flown over the sea. There was a systems failure and the drone pitched into the sea resulting in a watery grave. At some point later in time, the drone was recovered from the sea by a diver.
The camera was disassembled to investigate its condition. During that disassembly process by persons unknown, the Microbolometer ribbon cable connector was torn off of the PCB. This was likely the result of force being used to separate the chassis parts that were stuck together with silicone sealant. It became obvious after disassembly that the camera had suffered salt water ingress that created corrosion of the PCB's and aluminium chassis parts. The attached pictures were provided in an eBay auction in which the 'owner' was selling the mortal remains of the FLIR VUE.
So what failure modes are at work here and is the camera repairable ?
1. The type of fluid that contaminates the cameras internal parts often dictates the damage caused. Any fluid acts as an electrolyte and oxidiser around the powered electronics and chassis. Salt water is a very serious contaminant that causes much damage.
2. The camera still had power applied to it when it was submerged in salt water.
A combination of metals at different potential differences in a salt water electrolyte solution creates electrolytic action. The result of this is the erosion of the power traces, including IC pins ! While the potential difference is present within the cameras electronics electrolytic erosion of powered traces and leads continues. The longer the camera remains powered and soaked in salt water the more damage that will occur.
3. The Aluminium chassis of the camera will react with the salt water and oxidise. This is surface oxidisation and so of less concern with regard to repair.
4. The camera lens can contain Germanium lens elements. Germanium is a metal and will corrode if submersed in salt water for a period of time. The corrosion causes the anti-reflective coating to lift away from the lens surface, destroying the lens. Such damage cannot be reversed.
5. The FFC flag uses an actuator that is mechanical in nature. In the VUE camera, a micro motor is used to operate the flag. Salt water ingress into the motor can cause serious corrosion and destruction of the motor.
6. The PCBs used in the VUE camera are a combination of multi layer FR4 and FPC. Electrolytic erosion of the traces and layer interconnects within the PCB's can make the camera beyond repair. Such damage can be invisible from the outside and without camera schematics, faults cannot be traced easily. PCB damage beneath the BGA IC's requires those parts to be removed to inspect and repair the traces.
7. The TAU/VUE cameras use high density PCB's that are populated with modern physically very small components. Such components need significant rework skills in order to remove and replace them.
8. Poor disassembly trade craft lead to an important Microbolometer connector being ripped off of the PCB. The ripped pads may, or may not, be repairable on this multi layer PCB. Such repair would be quite involved and time consuming.
So is this particular FLIR VUE camera repairable ?
I rate this as a 50:50 case where the camera might be repairable if there is not too much electrolytic erosion of the PCB's. Sadly the damage is often hidden from view so an accurate assessment is not possible without having the camera on the test bench.
I actually bid on the auction purely in order to bring you, dear readers, an insight into the damage that can occur. I was considering the camera a write-off and so limited my bids. Others obviously had more confidence in the condition of the camera as the final bid was, IMHO, excessive considering the failure mode of the camera and visible damage to it. The microbolometer window was unusually contaminated which should not have normally occurred. How did dirt get onto the window I wonder ?
It is a pity that I do not have this camera in order to strip it down and show the damage caused to it by powered submersion in salt water, but I am able to produce this post detailing the horrors of such an accident.
Is the FLIR VUE ft for purpose ?
Yes and No.
In normal use in dry conditions the camera appears reasonably well sealed against the elements. It is not, however, adequately sealed for any form of fluid immersion ! Operation of this camera series over water does present the risk of total loss if the airborne platform enters the water, be it fresh or salt. Salt water is far more damaging however.
As has already been stated, FLIR basically adapted the standard bare TAU 2 chassis to be carried on an airborne platform. It was not protected by an additional layer of protection inside a well sealed plastic case. The camera and its connections should be protected behind seals made from contoured plastic mouldings and gaskets, not simple Silicone sealant. Such a protective casing need not be expensive or particularly heavy.
In short, if you cannot afford to lose it, do not fly a FLIR VUE over water ! As previously stated Sh*t happens !
Fraser
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