Unihedron
SQM-LU Users manual
5 Electrical connection
The SQM-LU uses a voltage regulator to bring the incoming USB 5VDC voltage down to 3.3VDC.
6 Mechanical installation
Unihedron sells an enclosure that is suitable for mounting either the
SQM-LE or SQM-LU into. You can read more about it, including
plans to build your own here:
http://unihedron.com/projects/sqmhousing/
6.1 Cover selection
If the unit is to be mounted in exposed location, we recommend an acrylic dome. Acrylic domes will
last 2-3 years but eventually weather on the surface. It is not clear that this will affect the reading much.
The best test would be to swap a weathered and new one back and forth when changing one out.
Presumably the main consideration would be to keep the domes clean every so often and to make sure
that the mounting plane is painted black to that it doesn't reflect light back to the inside of the dome and
then back into the meter.
Source of Acrylic domes:
http://www.globalplastics.ca/domes.htm
6.2 Cover calibration
Since the SQM-LU is not weather-proof, it must be protected in some way from the elements. A plastic
dome is recommended. This may reduce the incoming light by about 15-20%.
Because a covering will reduce the incoming light, the resultant reading will be darker (higher
magnitudes per arcsecond
2
value). The offset determined by a simple light experiment should be
subtracted from the reading.
A pending firmware edition will allow for built in manual offset. Apply this subtraction offset as a
negative value, i.e. if you measured 16.60 outside the covering, then 16.75 under the dome, then an
Revision 1.1
Page 21
Last modified: Jun 18, 2011
Illustration 3: Housing
