Power consumption related issues in thermal cameras can extend beyond battery run time as a processor or other VLSI that generates too much heat can be a challenge for the camera designer. Too much internal heating is the enemy of the designer because that heat either has to be transferred outside the cameras casing by some means or tolerated within the casing. Internal temperature changes and elevated temperatures around the microbolometer core can adversely effect measurement accuracy. Whilst radiometric thermal imaging cores take account of the temperature around the core, and sometimes the lens, it is better to avoid generating too much heat in the same space that the core occupies.
So how do you avoid excessive self heating and it’s negative effects on the core ? That is really a question for thermal camera designers but in my experience there are a few options......
1. Use the most efficient processor and VLSI technology available that can still provide the processing capability required, but is not excessively powerful for the task. The ultra low power, more thermally efficient processors can be more expensive than older, less power efficient processor designs though. Some manufactures will want to make that cost saving at the expense of thermal management !
2. Incorporate thermal transfer systems into the physical design to sink heat away from components that are generating heat and passing to an area of less thermal sensitivity, such as the outside of the cameras casing. Heat pipes, heat sink plates and even ducted fans may be used. It is just necessary to move the thermal energy away from the cores local environment.
3. Incorporate thermal storage into the design such that the thermal energy produced by the components within the camera is accumulated in a thermal reservoir that has adequate capacity to aid thermal compensation within the core. The thermal reservoir does not remove the energy within the casing, it just absorbs it, slowing any temperature variance experienced by the core to acceptable levels that may be compensated within the cores software.
4. Active temperature stabilisation of the microbolometer. This approach has fallen out of favour in some modern microbolometer designs due to the relatively high power consumption of the Peltier element incorporated within the cores design and the additional thermal energy produced But the Peltier element that must be dissipated within the case design.
5. The mainly software approach to internal heating within a thermal camera. This approach can include a combination of clever case design separating the core from the heat producing PCB’s, thermal throttling of the processor to manage its heat production, especially when full processing capability is not needed and temperature compensation tables that are used to correct errors in radiometric measurements.
6. No effort made to manage heat production within the cameras casing and only radiometric measurement correction tables used. This is a not uncommon approach by some manufacturers of budget thermal imaging cameras and can explain their somewhat less accurate radiometric measurement capabilities.
The Seek Reveal Pro contains a significantly more powerful processor chip and It’s casing gets noticeable warm during use. It is a sealed unit to provide weather resistance so the core and measurement software must cope with the elevated case internal temperature and heat produced by the powerful LED positioned next to it in the metal front assembly. It manages this task admirable
. The standard Seek Reveal cameras (non Pro) use a less powerful processor and do not suffer the same level of self heating found in the PRO model. It should be noted that handheld equipment can take up thermal energy from the users hand so this is also to be considered where internal temperature is concerned. A handheld device that relies upon its case for thermal dissipation can see that thermal path compromised by a human hand wrapped around said casing. Such effectively becomes a ~30C thermal blanket around the camera ! This is especially the case with the seek a Reveal design.
The environmental operating temperature of a thermal camera sold into the World market must also be considered. There are some very warm countries in the world and a design that can self cool and cope in a 25C environment using thermal radiation from its case, may not cope so well in 40C+ temperatures in the UAE, Australia or similar environs. Getting rid of excess thermal energy from a very temperature sensitive device can be a real challenge.
Fraser
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