Thermal control observations...

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DiligentSkies
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Joined: Wed Dec 02, 2020 10:46 pm

Thermal control observations...

#1

Post by DiligentSkies »

Dear Dr. Glover,

To the best of my knowledge I have a very stable platform in regards to SharpCap.

However, the thermal control features in SharpCap, only provides meaningful feedback results... "When I select a targeted temperature(turning off the auto temperature) and setting a targeted temperature."

That is all fine and dandy, since I can specify a cool down target temperature in steps towards a target temperature goal.

Still, the net result is to drive the cooler towards an all or nothing of cooling power achievement towards the given temperature goal.
Even, "If I am stepping down the temperature in increments."

To me it appears to me, " An all or nothing response."

There simply does not seem to be a happy middle ground of fluctuating the cooler power towards a STEPPED procedure manner for the QHY268c camera.

Meaning either the camera is cooling down towards a target temperature or it is not. And it does so very rapidly.

My MAIN concern HOWEVER, is when warming up the sensor after spending hours at a set targeted temperature back towards ambient temperatures.

My observation has been such that when warming up the sensor, either by stepped increments towards a targeted(higher) temperature to the ambient temperature or not is, "Irrelevant!!!"

AND IS NOT comporting to concerns expressed by QHY towards thermal shock avoidances.

The camera software simply responds by cutting off all cooling power to zero in the warming cycle. No matter what I do in the SHARPCAP software.

For all intensive proposes, "I could simply shut down SharpCap and allow the camera to warm up to the ambient temperatures on its own at this stage since any warming trend beings by cutting all power to zero.
Since that conforms to the zero power observation of whenever I set a temperature above the current cooled temperature.

I would expect, If thermal shock is such a major concern. The QHY268c camera thermal controls would respond by providing a warming trend that at a minimum provides some power to the cooler.

As it does not, as soon as I provide a warmer target temperature, the response is simply to cut of all power to the camera chiller and allow the camera to warm up on its own.

Meaning, if I am at zero degrees Celsius and selecting a temperature target of five Celsius, this new targeted temperature control responds by cutting off all power just the same if the targeted was set to ambient(room) temperatures.

Basically, "No matter what cooled down temperature achieved, when I attempt to warm up the sensor to ambient temperatures, the RESULT is to cut off all power... Such that the sensor warms up to ambient temperatures on its own gradient.

At this point, I would expect to have some power being applied to controlled a stepped procedure to warming the imagining chip that is adverse to thermal shock concerns.

My observational is such that the camera just warms up to ambient temperatures on its own gradient by reducing the power to zero whenever the target temperature is set above its current threshold temperature.

There appears to be NO power control to step backwards towards ambient temperatures.

The camera/sensor simply warms up to ambient temperatures on its own since all power is being cut off and the temperature of the sensor warms as no power is being applied.

That most does not comport to staged cooling/warming controlling trends one would expect with QHY docs stressing thermal chip shock!!

Currently, I am not sweating the details but in the back of my mind I am looking to preserve the longevity of my camera???

Sincerely,
Mark
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Re: Thermal control observations...

#2

Post by admin »

Hi Mark,

yes, I've just tested this and see the same behaviour with my QHY 174 (which is the only cooled qhy camera I have to test with). Basically if you increase the target temperature by more than a couple of degrees the cooler switches off entirely – it will then come back on as the new target is approached.

You have a couple of options to work around this – you can turn off the 'Auto' option on the cooler power control, which lets you take manual control of the amount of power going to the cooling system – you can then gradually reduce the power level to allow the camera to warm up gradually.

Another option is to try out the SharpCap 3.3 beta – the sequencer system in SharpCap 3.3 allows you to automate various steps of the observing process and one of the things it will handle is warming up the camera. In the very latest beta version I changed the warmup procedure slightly – now it gradually increases the target temperature (in 2C increments) over a period of several minutes. This seems to work fine with my camera – at each increment the cooler power drops by about half, but then recovered slightly as the sensor warms towards the new target. It certainly gives a much more gradual warming.

Finally, you have the option of going to QHY and asking them to put a better cooler power algorithm into their SDK – when the power is set to auto mode then all SharpCap does is tell the SDK the target temperature that should be aimed for – all of the fluctuations in the power that you are observing come down to the algorithm that qhy are using.

Cheers, Robin
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