In SX Microcontrollers, SX/B Compiler and SX-Key Tool, George Herzog wrote:

I acquired some TAOS light sensors that compensate by removing the IR from the total light for the sake of more accurate calculation of visible light.
 

My dilemma is their formula for converting digital readings into commonly accepted LUX values.

It goes something like this:

 

[Sensor0-Sensor1]x0.39xe[sup][0.18Rsquared] [/sup]

where R is equal to [Sensor1/Sensor0-Sensor1]

 

I know that it would be easiest to merely send the sensor reading to a PC and have the PC recalculate, but I would like to consider an off network microcontroller solution.

 

Since it implies natural log look-up tables are required, it would seem to me the SX-48 might be needed.  I guess all the multiplication could be handled with look up tables.  I am not clear on how to impliment a natural log table in binary.

 

I am also wondering if the natural log creates a greater burden than Base 2 log tables.  If that is the case, can I use Base 2 logs and insert a constant value for e?

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