 # What is the Threshold Value (250) in LM35 temperature sensor

In the Temperature Alert Project(uses LM35 sensor), what is the threshold value (250) given by us and how to convert it to degree Celcius?

Use the formula T=r/10.24, here ‘T’ is Temperature in Celsius, ‘r’ is Analog Pin Reading from Bolt. Hence by using this you will get the required Temperature reading in celsius. Also your thresold value 250 is T(thresold) = 250/10.24 = 24.414 C.

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For every +1 Celsius rise in temperature there will be +10mV higher voltage at the output pin. So if the temperature is 0◦ Celsius the output of sensor will be 0V, if the temperature is 10◦Celsius the output of sensor will be +100mV, if the temperature is 25◦Celsius the output of sensor will be +250mV.

So we are using 250 as the threshold Value which is 25◦ Celsius.
We can Calculate it by using the formula given below,

``````                      T=r/10.24
``````

here ‘T’ is Temperature in Celsius, ‘r’ is Analog Pin Reading from Bolt

Threshold value 250 is calculated as
T(threshold) = 250/10.24 = 24.414 ◦C which is 25 ◦C approx.

V OUT =+1,500 mV at +150˚C
= +250 mV at +25˚C
= −550 mV at −55˚C