I am a designer of detector that uses infra red pyroelectric sensors
to detect fires. One 'feature' of pyroelectric devices is they are
sensitive to temperature changes as they introduces a DC offset onto
the sensor output. If this DC component is too great it saturates the
sensor and it is effectively blinded.
This effect is more pronounced the lower the temperature. Since out
product is rated at minus 40 to +80 DegC, the danger areas are changes
between -20 and -40 DegC.
Now, Tests show the sensor will not saturate at ramps of 1/8th of a
degree per minute between -20 to -40 (thats 7.5 degrees per hour)
Although I can't do anything about the sensor saturation, I can put in
schemes that give notification of sensor saturation and suppress any
false alarms.
I don't want to do this extra work if it never occurs in real life
situations. Of course there will be warnings mentioned in supporting
documentation about artificially creating temperature ramps.
My question is as follows:
What sort of temperature ramps are experienced in locations where the
temperatures vary between 0 DegC and -40 DegC.
The following random musings may help..
I must discount locations where temperatures drop below -40 on a
regular basis as the detector is operating outside its rated
temperature.
This detector will be outdoors and protected from direct sunlight by
a weather shield.
Due to the low position of the sun, I guess there is a less extreme
difference in day / night temperatures than is seen outside the artic
circle.
If you are kind enough to respond to this posting, these are the sort
of things that would be useful
Temperature charts (excel?)
Links to relevant information
Your Opinions (please give me some clue as to where you gained your
experiences from)
I will check back on this posting now and again for the next six
months.
Many thanks in advance
Jon.

For email (work), use:
Email: jnewcomb_at_tycoint_dot_com
Change:
_at_ for @
_dot_ for .