PT100 with temp

[kumara]

Dear all
i want to interface (RTD)PT100 pic 16f877a .

[longpole001]

having a Very very quick look at the probe resistance table

http://www.micropik.com/PDF/pt100.pdf

it seem to move between 18R and 390R representing temps - -200deg C to 850Deg C.

You did not say what the pic voltage was , but assuming it at 5v i would connect the one side of the probe to the 5v and then to a resistor to ground and connect the joined point o the AN0 anaolog port

Calculating the resistor to ground using the voltage divider calculator

http://www.calculatoredge.com/electr...e%20divide.htm

i would start by using 390R 1% resistor , with the calculated values of 5v in , probe resistance range of Ra = 18R - 390R and the Rb being 390 this gives the voltage to the AD a range of 4.75V - 2.5v

i would setup the voltage reference on the pic to be VDD and measure the AD input ,

referring again to the probe table , its about 4R = 10Deg change , this calclulates to about 0.04v per 10 degrees using the above values , so depending on how accurate the probe is each 0.01v = 2.5degc change

setup a sample loop etc and average the reading

, have fun

cheers

Sheldon






it requires a connection of probe to voltage divider connected to one of the analog ports ,

[kumara]

can u give me another solution.

[longpole001]

no its the only way i know how to go about it

[aratti]

http://ww1.microchip.com/downloads/e...Doc/01146B.pdf
Read this documento, tip 13.1 and tip 13.2 seem a good solution to your application.

Cheers

Al.

[Acetronics2]

simply ...
http://ktylife.free.fr/vespa/Montages/PT100toADC.gif

alain