One of the main problematics is to ensure that the placement of the temperature sensors is at the most critical areas of the room. The casing in which the sensors are places is custom made by an extension RJ11 link.
While the sensors are able to serial connect (as described in previous blog entry) the RJ11 extender makes it possible to add multiple temperature sensors on every JeeNode.
Furthermore the actual placement of the sensor in the casing can have an significant effect on the actual measurement. The hypothesis is that a sensor placed on the outside of the casing has a better air circulation and – flow why this sensor must be capable of sensing minimal changes quicker than a sensor placed inside the casing with a closed environment.
We made several tests on the issue concluding the fact that the two links with sensors placed on the outside of the link did sense quicker and more precisely to changes, but while these changes lay in an interval of +- 0.2 degree we will conclude that it is not necessary to place the sensors on the outside of the link, causing both production – and lifetime issues.
BLUE : sensor placed outside
RED : sensor placed on surface of the extender
YELLOW : sensor placed inside.
Cold rooms can have various size dimensions, some like refrigriators others even as big as small containers. In common physics it is known that temperatures in a closed environment differs from bottom to top, where the warm air seek towards the top and the cold to the bottom. While measuring temperatures in such cold facilities, the exact temperature interval is highly important in sustaining correct vaccine conditions, it is therefore important to allocate the sensors by height.
A test made in an usual student dormitory room showed that this case is substantial. The three sensors is placed in the Top, middle and lower part of the room. When opening a window the temperature distribute as follow. From the test we can see how the cold air entering the room cools it from the bottom and up.
BLUE : placed in the top of the room
RED : in the middel of the room
YELLOW : in the bottom of the room