Hello
I am facing quiet a bit trouble with LM25 temperature sensor, The readings are a bit too high(90-120*C) for room temprature. I have tried following things to get an expected result but non seems to work
For stable Temperature Reading.
Adding Filter Capacitor at power rails of LM35:
The fluctuation of temperature output might be the noise available in power supply so it’s better to use an electrolytic capacitor at power supply i.e. connected to Vcc and GND of LM35. (I added 10 uF)
Adding resistance between output pin and GND pin
According to datasheet of LM35 it has low sinking capability as a result its output become more sensitive to electromagnetic interference. 1K or 2K resistor between output and GND can solve this issue to some extent and also solve self-heating error.
Taking average reading rather than single reading
Fluctuation or drift are one of the major issues of arduino sensor. One way to make fluctuation less is trying to calculate average reading instead of single reading.
Minimize the error
When we use default reference i.e. 5V refence at analog input, it is less sensitive to voltage difference. At this reference arduino can map 5V input voltage into 1024 steps i.e. 0-1023. This means resolution at 5V = 5/1023 = 4.88 x 10-3V = 4.88mV. So, if we use default 5v analog reference minimum temp deviation that arduino can detect is 0.50C. If we use default arduino reference voltage we will end up with adding 0.50C extra error.
This error can be minimized by selection proper reference value for arduino. I used 1.1V internal reference for arduino, so that the minimum temperature deviation that arduino can measure improves.
At the end I even purchased a new sensor assuming the frist one was faulty butthe is no avail!. I am still facing the same problem
It was be great if someone helped me out here
I am facing quiet a bit trouble with LM25 temperature sensor, The readings are a bit too high(90-120*C) for room temprature. I have tried following things to get an expected result but non seems to work
For stable Temperature Reading.
Adding Filter Capacitor at power rails of LM35:
The fluctuation of temperature output might be the noise available in power supply so it’s better to use an electrolytic capacitor at power supply i.e. connected to Vcc and GND of LM35. (I added 10 uF)
Adding resistance between output pin and GND pin
According to datasheet of LM35 it has low sinking capability as a result its output become more sensitive to electromagnetic interference. 1K or 2K resistor between output and GND can solve this issue to some extent and also solve self-heating error.
Taking average reading rather than single reading
Fluctuation or drift are one of the major issues of arduino sensor. One way to make fluctuation less is trying to calculate average reading instead of single reading.
Minimize the error
When we use default reference i.e. 5V refence at analog input, it is less sensitive to voltage difference. At this reference arduino can map 5V input voltage into 1024 steps i.e. 0-1023. This means resolution at 5V = 5/1023 = 4.88 x 10-3V = 4.88mV. So, if we use default 5v analog reference minimum temp deviation that arduino can detect is 0.50C. If we use default arduino reference voltage we will end up with adding 0.50C extra error.
This error can be minimized by selection proper reference value for arduino. I used 1.1V internal reference for arduino, so that the minimum temperature deviation that arduino can measure improves.
At the end I even purchased a new sensor assuming the frist one was faulty butthe is no avail!. I am still facing the same problem
It was be great if someone helped me out here