# About unit thousand in plant monitoring system

In plant monitoring system we are getting 1.02 thousand as maximum unit. Can you please explain about the unit? like intensity unit of light is LUX . And how this number related to environment condition ? like 1.02= sunny bright what about other number ranges ? like 855 or less. I found that the value is 10 bits representation . It is clear . My only concern about the ranges… form which to which value we can make that it is cloudy or sunny or night etc.

1.02 thousand or the values we get doesn’t have any unit. You have connected the LDR sensor to a 3.3V port via a series resistor and you are taking the voltage across the resistor via pin A0 with respect to ground. A0 pin has an Analog to Digital Converter (ADC) inbuilt which maps the voltage from 0-3.3V to a number ranging from 0-1023.

Resistance of the LDR sensor is inversely proportional to the intensity of the light, but we measure the voltage across the fixed resistance and not across the LDR and by voltage divider circuit we can observe that as the volage across LDR increases, voltage across the fixed resistor decreases and vice-versa. So we can in turn say that voltage across the fixed resistor is directly proportional to the intensity of light. So we can say that as the intensity of light increases in the environment the number increases till a maximum value of 1.02 thousand which is the maximum value 1023. If the number decreases that means the intensity of the light is decreased.

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@monish.speak2u thank you !

You are welcome @mondalsubha22111995