Background information
Reproducible image quality and high repeat accuracy are paramount in image processing applications, which is why the Baumer digital industrial cameras and vision sensors are designed for dependable 24/7 operation.
Ensuring specified quality, producing reproducible results, and maintainng flawless system operation depend on great many factors, among which one is fairely dominant: Operating temperature.
Unlike the common misconception, operating temperature does not mean the ambient or installation temperature, but rather the temperature at a certain measuring point on the camera housing. Why?
Temperature specifications in data sheets
Storage temperature
Not only for electronic appliances, temperature specifications refers to the temperature inside the device. Looking at the related component specifications one might think the maximum limit is easy to identify.
Operating temperature
However, in image processing it’s different. Numerous parameters, component layouts as well as ambient conditions hamper conclusions on the maximum ambient temperature based on component core temperature.
Core temperature depends on power consumption, thermal connection and component interaction. Operating mode and load have an influence on the power consumption of sensor, FPGA, interface chip modules, etc. which results in a variety of core temperatures.
Reliable operation requires observing the maximum limit of thermal stress imposed on the electronic components. Temperature tests during development specify the maximum limit at a specific measuring point on the camera housing.
The temperature gradient between the outside and inside of housing is known - at least when operating the device without any thermal connection or temperature-relevant measures - i.e. in a "worst case" scenario.
As already mentioned and shown in Figure, no conclusions can be drawn between the temperature measuring point on the outside of the housing and the ambient temperature, nor between the component core temperature and the ambient temperature. This is due to many unknowns in connection with the direct environment of camera or vision sensor: o What is the installation‘s heat capacity? o How long does it take the installation to thermally stabilize? o What is the holder geometry like? o What material is it made of?
Heat dissipation at cameras and vision sensors
The heat generated in the device spreads in every direction. Heat conduction occurs on surfaces that are in contact with other components of the system. On the remaining surfaces, the heat is dissipated from the camera by means of radiation and convection (see Figure).
Lens and cabling absorb part of the heat, but the major share is transported via the camera mounting.
Thermal connection
Temperature tests at design stage are performed without thermal connection. Such "worst case" scenarios do not represent true installation or operating conditions.
The Figure shows camera (1) and optics (4) mounted to a metal contact surface (3) with the camera holder (2) in between.
Since the majority of the generated heat is dissipated through the device holder, this is the central element of the thermal connection.
Design recommendations for camera holders
Material
High-conductive material is ideal, whereas low-conductive material will hamper heat dissipation.
Notice
Select a well-conducting material such as aluminum, copper or brass. Do not use insulators!
Design geometry
In addition to the actual material, design geometry of the camera mounting also signifiantly influences heat dissipation. Besides the material’s thermal conductivity, the contact surfaces of camera, holder and installation have a direct effect on thermal resistance and therefore heat dissipation.
Material thickness
Surfaces with good thermal conductivity
Thin materials transport heat very well, which why the camera holder should be as thin as possible for minimized conduction path between camera and installation.
Installations and machinery with insulating surface (e.g. plastic)
Here, camera holders may have a buffer effect and improve heat dissipation by
- absorbing and shortly retaining a certain amount of heat which
- dissipates via a poorly heat-conducting surface larger than the one of the camera
Additional cooling is recommended, e.g. by active cooling elements or ventilation.
Length
Thermal connection on high-conductive surfaces
Ensure a short holder design to keep the conductive path between camera and installation as short as possible.
Thermal connection on low-conductive surfaces (e.g. plastic)
Here, camera holders may improve heat dissipation by:
- Absorbing and shortly retaining a certain amount of heat which
- dissipates via the larger surface
Additional cooling is recommended, e.g. by active cooling elements or ventilation.
Contact surface
The camera holder design should ensure sufficiently large contact surfaces between camera, holder and installation. The camera should fully rest on one lateral surface.
Related Topics
Support
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