Hello all.
I need to design a circuit for PT-100 without any transmitter and all and get the temperature using Arduino nano.
I have used the lm358 but it didn't work.
Please help me with this..
Thank you

 

Show us the schematic diagram of the electronics and a listing of the software you tried. What didn't work?

 

Show us the schematic diagram of the electronics and a listing of the software you tried. What didn't work?

Sure here is circuit diagram attached
here i am using LM358

 

" a circuit for PT-100 without any transmitter "??
OK, the TS is assuming that we all know what is PT-100. My mind-reading skills are way too weak for that.

 

I have used the lm358 but it didn't work.

That tells us nothing.
How can we help you, if you give us no information about what/how it didn't work?

 

Unfortunately, due to several overseas fake component sellers, a PT100 today could be anything.
I assume the OP is talking about something like this: https://www.mouser.com/pdfDocs/PT100_DATA_SHEET.pdf
https://www.analog.com/en/technical...og-feedback-compensates-pt100-transducer.html

 

You gave us very little information so I am assuming that you are using the following link:
https://bestengineeringprojects.com/measuring-temperature-using-pt100-and-arduino/

So what is not working? Have you made any measurements on the circuit to make sure it is wired correctly?
The output of the voltage source should be adjusted to 0.4545V with reference to circuit common.
The output of the PT100 unity amplifier should vary when you warm or cool the sensor.
If both of those measurements appear to be correct, measure the voltage on A0 on the arduino. It should vary by about 4.7 times more than the output of the PT100 amplifier.
Is the display showing anything?

 

OK, now I recall some ancient history, in which, at that time, "PT-100" meant a 100 ohm platinum RTD (Resistance Temperature Device). Those were the standard of accuracy for measuring temperature. But they did require an accurately regulated constant current source because they do not generate any output voltage by themselves.
In addition, there is a reason for providing two connections to each end of the sensing resistance, which is to be able to avoid the effect of changing temperature on the resistance of the connection wires. But a nuts and volts article would never consider that fact.
A KELVIN connection arranges for one set of leads to supply the current through the 100 ohms resistance while the second set of connections allows the voltage developed across the sensor resistance only to be measured. That avoids a large and well understood source of error.

 

It's not ancient history. Some very expensive PT-100 devices are used today to regulate wafer furnace temperatures.

https://www.vulcanelectric.com/products/semi-fab-process-sensors/
https://www.vulcanelectric.com/wp-content/uploads/2017/08/sensorbrochure-1.pdf

B
Platinum 30% Rhodium(+) 2500-3100F
Platinum 6% Rhodium(-) 1370-1700C

 

Hi warm,
Your circuit is for a PT1000 not a PT100, R1 needs to be changed.
E

 

Hi warm,
The coding for a PT1000 on the circuit is incorrect, the circuit is designed for a PT100
This is a LTspice simulation of your circuit, I have disconnected the capacitors.
The Vadc will not go down to zero volts with a single power rail.
The Vadc range is +0.15V thru +1.3V

The Blue voltages Vpt and Vr show the values for 0Cdeg
The capacitors may cause you a response time problem.

E

 

The LM324 is not a "rail to rail" device anyway, but it does work well with a bipolar supply, but not represented as a precision device. And without a regulated current or a Kelvin hookup do not expect the high accuracy.

 

Hi warm,
The coding for a PT1000 on the circuit is incorrect, the circuit is designed for a PT100
This is a LTspice simulation of your circuit, I have disconnected the capacitors.
The Vadc will not go down to zero volts with a single power rail.
The Vadc range is +0.15V thru +1.3V

The Blue voltages Vpt and Vr show the values for 0Cdeg
The capacitors may cause you a response time problem.

E
View attachment 301634

Yes, slope and value of C is not correct It gives large difference .. so any idea how fix it. I have tried some different values but after few seconds it get distorted

 

Hi war,
I have used the PT100 on other projects, the value of C1, 100u is much too high a value.
A 100nF would be sufficient also the 220K is too high, the ADC expects a Zin of 10k or less.

E

 

Hello All
Basically, I am designing the circuit for PT-100 so that Arduino can read the temp using the one of these ADC's (say A0)
I have designed the circuit as the schematic attached and sense the voltage of the output pin using arduino (Internal Ref i.e. 1.1) and used the couple of equations to get the
Resistance form voltage
Volts = (analogRead(Vin)/1023.0)*1.1; //converting bits of voltage into voltage
// Serial.print(" Volts : ");
// Serial.print(Volts);
Res = Volts*slope+C; //y=mx+c here slope=48.5 and c=110

after getting the Res
Res to Temp
temp1= (Rx/R0-1.0)/alpha; // from Rx = R0(1+alpha*X) R0=100 , alpha= 0.00385
calibration=0.3+(0.005*temp1); //tolerance for class B PT100
tempC=temp1-calibration; // Final temperature in Celsius

but now as i power on the circuit, the temperature is constant.
Note - I test the coding logic with some random value and it is correct for example if Re = 100 so temp should be 0 which is correct, and we can check for some other values too
but i dont get the proper Res value and i don't know that is it code logic not working or circuit needs some improvements
bcz i dont have proper instruments to diagnose. My multimeter can only measure up to 2 decimal digits.

 

Hi warm,
I have pointed out to you that the 220k R7 is too high a value, the datasheet recommends not more than 10K.
Also, the 100uF is not suitable, disconnect it.

Rerun your tests and post the results at 10C intervals, I can the check.
Post your Arduino sketch


E

 

For the circuit posted in #15, remove C2 and change R7 to zero ohms. Also remove C1, across the sensor.
What voltage do you see on the outputs of U1 A and U1 B?

 

Hi warm,
This is simulation using the PT100 formula.
Note: R6 and R3 are 3k3 in first simulation

E

 

In a simulator such as this one, all the supply voltages are perfectly stable and connection wires are not affected by temperature changes. And there is no external noise.
To allow for zero degrees C to provide 0.0 volts out, the op-amp negative supply voltage should be negative 5 volts, or so. That will allow for a zero voltage output quite well.

 

Bill,
I am fully aware of the limitations of the simulation,
The TS states his circuit does NOT WORK, I am trying to help him understand why .!
He is also aware he cannot have a zero Vout.

What is the point of your post?