Thermistor or LD35

[Newbiesss]

hi everyone,

just wanna know more about how thermistor and ld35 work.
which one is more suitable for human temperature measurement?
and how do i measure if im using thermistor and the way ld35 measure the temperature. by skin contact to human body? or how?

and which type is more suitable if im building it in my project with pic?


pls provide me some solution/website/code/circuit/schematic diagram of the thermistor or ld35 which implement with pic and show the temperature on the pc.

any of suggestion is much appreciated.


thanks!

[temtronic]

first...
This forum is about using CCS C to create programs for PICs, not a general Q&A electronics forum.

That being said and assuming you meant LM35 and not LD35, either will work for your project depending on the time constant you require for the readings. Obviously the thermistor will be faster(if the bead style) and may be easier to attach to your skin.
From the code perspective, the LM35 is a linear device, easy to cut code for( several examples are on the 'net'). Thermisitors require more code and overall design.Selection is the challenege, then it's just a matter of code cutting based upon the manufacturers datasheets.

Calibration is the key to either device to get accurate readings and of course the actual hardware construction is important (noise,EMI,line loss,etc).

I'd be inclined to use an NTCLE203E3103FB0 thermistor (10K leaded) unit from Digikey (BC2299-nd).Cheap,fast,easy to use for your application.

The choice is yours...1,000s exist !!!

[Stormrider]

I was setting up the ADC of my 16F887 to interface an LM35 also, but found out I had some error margin when reaching the max reference voltage, and the LM35 has a sensitivity of 1°C/0.1V so I was not very suitable for me. I know I have to work out the ADC to make it work better, but in the end I chose to use a Maxim DS1631 Digital Thermometer. It uses I2C and sends 1 o 2 bytes to the PIC to make temperature readings. Is fairly easy to use, just get the DS1631 datasheet and application note from Maxim and read the CCS manual on implementing I2C.

Good luck with your project!

[edit]
The DS1631 IC's flat surface makes it great for human temperature readings, when I put my thumb over it it read about 29°C, it has a great response and sensitivity.

[bkamen]

[Stormrider]