Re: QHY8 Pro and MaximDL


Aug 18, 2011

 


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#46472 Aug 18, 2011

I've just acquired a QHY8 Pro and hooked it up to Maxim. It works, however, the TEC is very slow to ramp up its power to get the temp to its set point. Then when it gets to the set point, it ramps down so slowly that it continues to drop the temp. Is there a setting that would allow the temp to ramp up and down like other CCD cameras I've used?



Thanks!



David



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#46473 Aug 18, 2011

On 8/18/2011 1:10 PM, David wrote: >

> I've just acquired a QHY8 Pro and hooked it up to Maxim. It works,

> however, the TEC is very slow to ramp up its power to get the temp to

> its set point. Then when it gets to the set point, it ramps down so

> slowly that it continues to drop the temp. Is there a setting that

> would allow the temp to ramp up and down like other CCD cameras I've used?

>





Temperature control is done by the drivers from QHY, not by the camera

control program. All MaxIM can do is tell the driver the target

temperature, and the driver controls how it gets there.



I've asked QHY in the past for better / smarter control over temperature

acquisition, but they seem to think that it is "good enough", and don't

plan to make changes.



To avoid overshooting when first firing up for a session, gradually drop

the set point, to avoid the TEC power from overshooting the number where

you know, based on experience, it will settle. For me, to hover at -10C

requires around 27% TEC power, so I don't want to just start at -10C

setpoint, or the power will quickly be set above 27%, and won't come

down until the camera passes -11C. Instead, I'll come up in 5C stages,

thus ensuring that the camera never exceeds 30% TEC power. Then, when I

finally get to -10C, I don't overshoot.



Hope this helps. Hope more people ask Dr. Qui to make such a change,

perhaps as simple as allowing at the driver level a "maximum TEC power %".



Jeff



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#46474 Aug 18, 2011

Thanks, Jeff! Ya' gotta' love the logic of your process to solve the overshoot. Terrific!!



David

--- In MaxImDL@yahoogroups.com, Jeff Woods jeff@...> wrote:

>

> On 8/18/2011 1:10 PM, David wrote:

> >

> > I've just acquired a QHY8 Pro and hooked it up to Maxim. It works,

> > however, the TEC is very slow to ramp up its power to get the temp to

> > its set point. Then when it gets to the set point, it ramps down so

> > slowly that it continues to drop the temp. Is there a setting that

> > would allow the temp to ramp up and down like other CCD cameras I've used?

> >

>

>

> Temperature control is done by the drivers from QHY, not by the camera

> control program. All MaxIM can do is tell the driver the target

> temperature, and the driver controls how it gets there.

>

> I've asked QHY in the past for better / smarter control over temperature

> acquisition, but they seem to think that it is "good enough", and don't

> plan to make changes.

>

> To avoid overshooting when first firing up for a session, gradually drop

> the set point, to avoid the TEC power from overshooting the number where

> you know, based on experience, it will settle. For me, to hover at -10C

> requires around 27% TEC power, so I don't want to just start at -10C

> setpoint, or the power will quickly be set above 27%, and won't come

> down until the camera passes -11C. Instead, I'll come up in 5C stages,

> thus ensuring that the camera never exceeds 30% TEC power. Then, when I

> finally get to -10C, I don't overshoot.

>

> Hope this helps. Hope more people ask Dr. Qui to make such a change,

> perhaps as simple as allowing at the driver level a "maximum TEC power %".

>

> Jeff

>



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