Solar sensor saturates

rkeith

New Member
Hi All,

I am a newbie here. I had a quick look for a resolution to this problem. Please excuse me if it has an obvious answer.

I am writing a dll for a client so he can use a number of HobbyBoards products with LabView. I write my code to run directly on the TMEX drivers under Windows with no Java, OWFS or other bloat. One of these sensors is the solar sensor. I set it up yesterday to test under some "real" sunlight; 1,000 ft. elevation, mid 90s (F) and under 20% humidity and very little smoke and haze. The reading rose to 300 mV and then went to -250 mV shortly after midday. Putting a piece of translucent plastic in front of the sensor brought the reading back "down" under 300 mV.

These readings were identical for both my code and the old Ibview32.exe 1-Wire Viewer.

Is this the expected behaviour for this unit or is the one I have faulty? Is anyone able to explain the -250 mV reading.

Thanks in advance,

Robert Keith
Thermodata Pty Ltd,
Melbourne, Australia
 
Robert,

This in known behavior. The sensor will saturate when exposed to high light levels. The best way to prevent this is to filter the light down like you have done.

Eric
 
I found that an old pair of lightly tinted safety glasses made a great filter. I have mine mounted on my solar hot water panel, which is tilted at latitude (about 40 deg). At high noon, clear sky, low humidity, the sun is just about perpendicular, I get about 240 mV, so I'm using most of the scaled range.

Now if only I can calibrate mV to solar thermal energy...
 
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