[SOLVED] Temperature measurement at: 120-165 °C

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hello,

you need to use PT1000 (easier as PT100)
or themocouple type K.
and an amplifier..to get a voltage ouput of 0.. 5v
or 4-20mA on R=250 ohms
 

The LM35 has a specification up to 150°C. And if you take a look at the curves in the datasheet, it shows graceful degradation beyond 150°.

I think you should be OK.
 

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    laos

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I know. But I talked with the user. They says they will use around 100-125 C. But they want the capacity up to 150 degree C. I think it should work.
 

Having trouble with LM35. Its has melted!!! I think I've to use PT100. But the link you posted is not clear for calculation. I also trying from this: https://www.picotech.com/applications/pt100.html.

But I'm confused about how to measure. Its just a tiny change in resistance there. Should I use any Op-Amp to multiply by 10?
 

hello,

yes you have to use constant current generator or a bridge to use Pt100.
You can also use PT1000 ( 10 times PT100) to avoid problem (less problem) wuth the length of cable.

View attachment Pt100_docu.pdf
you can see Instrumentation AOP or normal AOP to use Pt100 (Pt1000) in a bridge.
There is also some industrial converter to convert Pt100 to 4-20mA ..into R=250 gives 1-5V (cost is less than 80€ .. xx$)

what accuracy do you need ?
if not so critical you can use this example (schematic) with a classic Ampli OP ( used for hetaer control)
and adapt the range .
 

Woo hoo. That is the formula for +ve temperatures. :grin:

Tell me the range of temp you are measuring. I will write the code. Post your project files.
 

I was fool. Tried to measure the temp using just voltage divider like: This. Just replacing the thermistor by PT100. But when the wrong data comes out I was confused. Still now I'm trying to do that calculation like a fool. But I'm looking for a simple solution...
 

tell us what is the range of measurement ?
what accuracy do you need ?
so, maybe you can use a simple solution : a quasi-linear response formula type y =ax+b easy to code in C
Delta is less than 2% in the range 0 to 180°C

or more precise :with a polynome formula.

don't forget, Pt100 itself has a accuracy domain.. depending of the class A, B or C
model A for the best accuracy, but also more expensive cost.
also, what length of cable beetween sensor and electronic conditionner input ?
 

I need to measure in range 100-165°C. Need not so much accurate but not more than 5% tolerance. I tried with the code I posted.

I found the relation that the voltage is changed as 1.4mV/°C. Depending on this I tried to calculate the voltage from the divider and then convert it to temperature dividing by 1.4mV. Unfortunately it shows data that is not accurate:-(.

Now suggest me what the way I can do a clean measurement?
 

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