PT100 with PIC microcontroller

[drbizzarow]

Dear ALL,

i need a cisuit PT100 temparture sensor using pic ADC. your help will be highly appricated

Regards

 

[IanP]

"PT100 RTD Evaluation Board"
https://ww1.microchip.com/downloads/en/DeviceDoc/51607a.pdf

 

[drbizzarow]

thx IanP

any one here to share practically used circuit ?

 

[IanP]

Here is a nice example of a compensated, opamp-based circuit that interfaces the PT100 to a microcontroller ..
**broken link removed**
It's based on MAXIM opamp, but I can't find any reason why it wouldn't work with any other rail-to-rail device ..

Here is another one: "A precision interface for a Resistance Temperature Detector (RTD)"
**broken link removed**
Again, you are not obligated to use the specifically indicated opamp .. any rail-to-rail will do ..

IanP

 

[internetuser2k11]

Can I use 741 Op amp with the circuit shown here

What changes should I make to the circuit?????

 

[IanP]

Can I use 741 Op amp with the circuit shown here

What changes should I make to the circuit?????

This circuit [pt100-precision-interface...] is designed to work as an instrumentation amplifier, and some of opamps’ inputs work with voltages very close to 0V/GND. For that one needs a rail-to-rail opamp.
The LM741 has a minimum supply voltage, which from the top of my head is somewhere around +/-6V, that makes 12V single voltage configuration.
If you want to connect output of [pt100-precision-interface...] to a microcontroller it has to be supplied of a single 0-5V power source. In this instance the LM741 is completely useless.
Google for a rail-to-rail in/out opamp that is meant to work with single supply rail ...
:wink:
IanP

 

[internetuser2k11]

OK. I used the same OP AMP as mentioned in the circuit. It is working fine. I want to know the exact o/p it gives / degree centigrade rise in temperature. including the increase in RTD resistance with increase in Temperature.

How much does the resistance of rtd pt100 increase / degree C.

what is the formula to be used with the above circuit for calibration???????????

---------- Post added at 11:39 ---------- Previous post was at 11:17 ----------

Also I want to know the value of C1 @ this link

Is it 1F or 1uF?

---------- Post added at 13:11 ---------- Previous post was at 11:39 ----------

Here is a nice example of a compensated, opamp-based circuit that interfaces the PT100 to a microcontroller ..
**broken link removed**
It's based on MAXIM opamp, but I can't find any reason why it wouldn't work with any other rail-to-rail device ..

Here is another one: "A precision interface for a Resistance Temperature Detector (RTD)"
**broken link removed**
Again, you are not obligated to use the specifically indicated opamp .. any rail-to-rail will do ..

IanP

What is the o/p mV/Degree C of the above circuit?

The o/p of the circuit is not linear. What is its o/p formula?

---------- Post added at 14:28 ---------- Previous post was at 13:11 ----------

What is the equation for the circuit

The o/p is not linear.

 

[internetuser2k11]

The circuit shown here is giving an o/p of 0.01V @ 850 Degree C.

I am getting wrong value. Please help me with the circuit. Tell me how to get the rtd pt100 resistance and temperature from Vo.

 

[mav1234]

@internetuser2k11 - How did you get the actual temperature value from Vo? Did you build a look up table? Where to find a look table for PT100 RTD - from the manufacturer?

 

[js]

vishay have nice application notes and informations:
https://www.vishay.com/resistors-non-linear/
https://www.vishay.com/resistors-non-linear/curve-computation-list/
you get excel table .... insert your sensor data and you get values....

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