NTC temperature monitor

[samuel.sam77]

Hi any one help me

i want to monitor the temperature(over heat in my circuit ) is there any formula

my NTC data 25c @10K
operating temperature -40C to 125C
beta value (25/85c): 3977K+/-1%

tolorance +/- 5%:
+5v
|
\
/NTC
\
/ 1K
|--------------/\/\/\-----to uC input
|
/
\10K
/
|
|oV


5v to ntc to 10K gnd 1k to uc

 

[MikeMl]

Here is what you can expect. Very non-linear circuit when you try to operate over such a wide temperature range.

 

[ericgibbs]

hi sam,
Look here.

Enter your thermistor values.
E
EDIT:
This image shows what the typical response would be of the Thermistor, just add your top 1K resistor value.

 

[samuel.sam77]

Here is what you can expect. Very non-linear circuit when you try to operate over such a wide temperature range.

Here is what you can expect. Very non-linear circuit when you try to operate over such a wide temperature range.

thanks for reply mike i need the conversion code
from reading adc input to temperature monitor
adc input 10-bit
vref -5v

how to convert 0-1024 to temp -40 to 120 degree Celsius

 

[Wp100]

Hi,

The resistor matching the NTC needs to be a multiturn trimmer to allow you to calibrate the ntc to your software.
Using a 5k resistor and a 10k trimmer gives you a broad adjustment range

 

[ericgibbs]

how to convert 0-1024 to temp -40 to 120 degree Celsius

If you set the therm/resistor circuit to give an ADC count of 800 at a temperature of +120C, this would give a resolution of 5 count bits per Cdeg.
So by multiplying the ADC count by 5, would make integer maths possible in the PIC

You would still have the original non linear temperature response of the thermistor.!
E

 

[samuel.sam77]

Here is what you can expect. Very non-linear circuit when you try to operate over such a wide temperature range.

R=Ro*exp(B*(1/K-1/298.15))

You mentioned K=Temp+273.15

what is the temp value here

R0-10K
B-3977
K-temp+273.15

 

[ericgibbs]

hi,
K= Kelvin temperature based as 273.15C degrees equals 0C degrees Celsius

So your lower temperature K= 273.15 -40 and your upper temperature K= 273.15 +120

 

[large_ghostman]

just thinking out loud but do you actually need such a huge range? i am using thermistors in one of my projects and to make my life easier i have narrowed down the range, for example you said that it's for a temp over heat in a circuit! and i notice you live in india, now i have never been there and know very little about india but will your circuit ever be exposed to temps anywhere near -40?
all i am thinking is if you can narrow the band down you have the option of a look up table. also better resolution, or maybe you just need whole degrees and can do without for example 25.6C if thats the case it would make your maths a bit easier.
that tool uncle eric pointed to is the business! saved me loads of time and effort!