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Introduction

In order to study the capability of the cultures to absorb energy coming from sunlight depending on their coloring, we are going to measure the temperature that the cultures reach compared with others control know-color cultures. These temperatures are measured by a system of thermocouples.

The tree main parts of the Microbial Albero Recorder.

For this objective, it has been designed a dish in which our E. Coli and yeast cultures are studied. There are as well two reference cultures: one entirely black and another totally white. The cultures are exposed to radiation coming from sunlight. All cultures are previously kept in constant and known temperature.

In order to make sure that the temperature differences among the cultures are due only to albedo effect, two strategies have been designed.

1. Several light sensors have been laid out symmetrically. The signal received by these sensors is transmitted to an electronic circuit which produces an electric response that finally ends up in the datalogger
   

   

   Layout of the thermocuples and light sensors.
2. Several thermocouples are arranged surrounding the cultures to make sure that the external temperatures are equal for all of them. We used our temperature mesurement system in order to accomplish this task.

Therefore, any temperature difference between the cultures has to be produced by the capability of absorbing light. This temperature is then measured by another thermocouple inserted into the culture. Furthermore, all this data is recorded and shown in real time through a computer screen.

Mesurement System

The aim of this part of the project is to quantify the difference of albedo depending on the color of several cultures of microorganisms.

In order do this, we need to measure two types of magnitudes: the amount of solar radiation that reaches the cultures (illuminance) and internal and surrounding temperatures of the cultures. This is because we propose that if the surrounding temperature of the cultures and the incident solar radiation are the same for all the cultures, then our Microbial Albedo Recorder system can estimate the albedo difference between those cultures, because the difference in the internal temperatures will be due only to the albedo effect.

Light sensor

With this electronic circuit we aim to adecuate the signal coming from the light sensors (photodiodes). This will make the signal useful to real time adquisition and ionterpretation.

A photodiode can behave in tho very diferent ways, depending on the conection configuration: photoconductive or photovoltaic mode. We are interested in the first one, because it make posible a precise and stable relationship between the energy of the incident radiation and the output current.

The following figure shows the equivalent circuit used in the simulations and the caracteristic curve