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How to interface B type thermocouple with pic16F877A?

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Saad_111

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Hi
I want to interface B type thermocouple with pic microcontroller 16F877A, as i am new to thermocouples so please help me, how to interface it, if anyone can post the circuit, it will be useful for me. reference table link of B type thermocouple is

**broken link removed**
 

Thanks a lot, can you please give a simple schematic of how to interface a thermocouple with mcu, i just need an idea, any of the thermocouple you can use, i need a sceamatic plz
 

yes .. the application note from microchip (in the first link ) has schematics for ADC interface
basically you just connect the amplified signal to one of the ADC pins of the MCU

this circuit from page 4 of the pdf
 

the highlighted resistor creates confusion, what is this? either this is a part of thermocouple or we have to connect it externally? because the thermocouple has only two outputs. thanks for your co operation

 

:roll: did you really bother to read through the pdf
that is a thermistor - meant to provide a temperature reference
 

Dear amu_cpln,
if I use a type B thermocouple, which gives 0V between 0 °C and 50 °C, is needed the cold junction compensation? if yes what is its temperature coefficient?
Thank you for reply.
Roberto
 

hi rbacchi,
sorry for late reply
was away for a days
the question doesnt make the requirement much clear - but i assume some info shall help
Cold junction compensation is meant to improve accuracy in thermocouple reading, the actual reading of thermocouple is proportional to temperature difference .. (rather than only the temperature at hot junction) - there are other ways to achieve this compensation also .. a search would provide you many such techniques (even without the use if extra thermistor)
 

Thank you amu_cpln,
my question is deeper.
I know how to compensate cold junction (also used with K and S types). But this is the case of type B thermocouple. It's caracteristics show a voltage near 0 from 0° to 42°C. What is the contribute of the termerature sensor in this range?. If I think the input socket at a temperature between 0 and 42°C, can I exclude the compensation?
Thank you for reply.
Roberto
 

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    rbacchi

    rbacchi

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Thank you FvM,
in your link I've found the answer!
Bye, Roberto
 

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