As I mentioned previously, I
purchased my SAM III partially completed. What is was now required was the
construction and installation of the sensors. The 3 sensor unit is
designed for X, Y and Z axis orientation. That is, N-S, E-W, and Up-Down.
The sensors are known to interact with each other so they must be spaced a
minimum of 15cm from each other. The easiest way to mount these units in
this fashion seems to be the use of Electrical junction boxes and conduit.
In this case I have chosen 20mm conduit and connectors (as opposed to the larger
25mm). The sensors need to breath and in this case the conduit provides a
couple of mm gap all the way round.
Figure 1: The framework in which the SAM III
sensors will be mounted (X and Y are the wrong way round in this image)
The second aspect of
construction and installation is the need to keep the sensors in a temperature
stable environment. Many users of the unit have gone to the extent of
burying their units 1.5m or more into the ground. Well I didn't like that
option so will be experimenting with an indoor installation. My Sensor
mount fits nicely inside a 27 L Esky (Cooler for our US friends) and this Esky
will fit nicely into a top shelf in a cupboard in my study. I will need to
fill the Esky with more insulation material but it will do as is for my initial
setup and trial.
Figure 2: The Sensor mount inside a
20L Esky (Cooler)
Figure 3: 'Second Light'. The SAM III
is up and running and logging data
Wiring the sensors was an
issue. The manual suggested solder terminals at the sensors but this would
require a 'permanent' joint. I chose to use terminal blocks located at the
central junction with 15cm long plugs to reach each sensor case. This
makes the unit easily dismantled and modified if there was a need. Each
sensor had it's own shielded 4 core 22AWG cable (Pro quality microphone cable in
this case). Quality shielded data cable is very expensive by comparison so
I hope this wire (for my short, less than 2m runs) will suffice.
I have yet to devise a suitable
mount for the actual sensors. Fat plastic cable ties act as holding clips
for the sensors so it is now just a matter of finding a means for securing these
to the casing.
This setup proved unsuccessful
as there was insufficient insulation/isolation in the sensors. 2-3 degree
C fluctuations occurred between approx 13:00 and 22:00 UT when the temperature
in the house was not stabilised by the air-conditioning. However, during
the rest of the time, the SAM unit performed well. A new means of
insulating/isolating the sensors and logging the temperature has been devised -
see Part 2.
Figure 4: Sample output from the SAM III
during initial settling in period (more than a day is required in a stable
environment for these sensitive devices to stabilise.
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