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Friday, January 27, 2012

From morning until dawn - and entire day described in seconds

Time lapse video sequences can render exciting results, for the visual impact these provide. While simply being a sequence of frames more separated in time than in a conventional video, once played back at the rate the human vision considers smooth (30 frames per second) these provide a view of the world that a human cannot easily perceive directly, given the comparatively fast rate at which he summarizes and retains information. For instance a cloud in its pass has very complex yet slow changes in shape and trajectory. These are very hard for average humans to perceive, memorize and mentally reconstruct as an animated sequence of events. In general, slow changing processes are inherently hard for humans to characterize in its dynamic nature.

As such it is not surprising that a video containing nothing more than a reproduction of the real world can be appreciated by humans as being somewhat surreal, when simply the only difference is the rate at which information is sampled and later reproduced.

The first video contains about 20 hours of footage shrunk to 32 seconds. It reveals one angle of the Almada city at the south of Lisbon, where part of the 25 de Abril bridge and the Cristo Rei can be seen. It is a typical winter day in Portugal, where the fog floods the morning and a passing of dense clouds fulfills the entire afternoon. This typical day is however solitary in a atypical winter month padded with bright sunny days and mild temperatures.



The second video taken during the 27th January 2012, reveals a clear night transition to a bright winter day in the city of Almada, just south of Lisbon the capital city of Portugal. At the bottom right, the horizon is cut by a huge rectangular crane belonging to a long time decomissioned shipyard.Its name was Lisnave and would once be an important maritime reference for large ships and oil rigs which would stop by for major repairing and overhauling.

Wednesday, December 21, 2011

LENA - Now featuring dose measurement

The DOSE feature discussed in the previous post is now done. Taking into account the GM tube characteristics, a realistic measure of radiation dose in uSv/hour is now being calculated, based on the single event rate. From the information obtained on the internet regarding the SI-39G tube, the value of 0.00049 uSv per pulse was taken into account for the calculation of the dose.

Additionally, another mode usually found in most Geiger counters and dosimeters is the CPM (Counts Per Minute) mode. It provides a relative measure (that is of course GM tube dependent) of the radiation exposure, based on the ammount of particles detected by the tube. In this case these can be either Beta particles with more penetrating energy, and Gamma photons. Alpha particles cannot be detected by this particular tube (the SI-39G).

Friday, December 16, 2011

LENA - The Geiger Counter that was finally made portable!



With the Geiger Muller tube module having been posted in a previous post, namely here, another important development was missing. While fully functional at that time as a sensor device which could readily be interfaced with via I2C, or having the pulses be directly picked up via a dedicated TTL signal, by itself the device could not be carried on the field and be expected to operate without additional hardware.