Re: [ATM] IR pyroelectric detetors

[David Nicholls <dcn@dcnicholls.com>]

Mark Holm wrote:
> Michael Lindner wrote:
>> David Nicholls wrote:
>>> I was wondering if anyone has 
>>> used the pyroelectric sensor from a movement detector as a way of 
>>> measuring mirror temperature for a cooling fan controller?
>> I have used this product:
>>
>> http://www.radioshack.com/sm-non-contact-infrared-thermometer--pi-2103171.html
>>
> Since the infrared emissivity of mirror coatings is low, and
> reflectivity high, I wonder if this idea doesn't end up measuring the
> temperature of the surroundings reflected in the mirror rather more than
> the temperature of the mirror?
> 

Confirmed. I just tried measuring the apparent temperature from my Newt 
secondary, and it is definitely seeing reflected IR.  The rear of the 
primary mirror, however, does show its true temperature.

I used a gadget similar to the one Michael described, in this case 
http://www.jaycar.com.au/productView.asp?ID=QM7225

DN

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David Nicholls
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