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Topic: PT100 sensor - help a beginner? (Read 29 times) previous topic - next topic

Nick_Pyner


By setting my reference to that 1.1V (on a mega you need INTERNAL1V1 and not just INTERNAL) I got a reasonably accurate meter just from the sensor and a couple of resistors, no need for op-amps or anything. Because I will be using this in a normal baking-oven project, I don't need that accurate readings. The cake won't care if the oven is at 225*C or 223.4*C... :)


Glad to see it worked out so simply. I have decided to use mine after all but I need the accuracy and am only working 1 > 40C, so I am just planning a board to take the amplifiers etc.

Xartec

A 'little' late, but based on "just started to give me strange values in the Serial Monitor (in the range of 70-90)" in the first post, wasn't it simply giving Fahrenheit instead of celcius (roughly 20-30)?

I need to measure the temp of a water solution with 1 decimal accuracy, so it needs to be waterproof as well. That means in my case the PT100 is the way to go right?


Nick_Pyner


I need to measure the temp of a water solution with 1 decimal accuracy, so it needs to be waterproof as well. That means in my case the PT100 is the way to go right?


No, and not necessarily.

It is commonplace to put temperature probes into thermowells. No waterproofing needed.

Now that we are in the 21st century, I'm not sure you would ever use a PT100 in favour over the DS18B20 unless you had persuasive reasons in the light of the shortcomings of the latter.

The DS18B20 operates from -55 to 125C. I don't know what the range of the PT100 is, but it's a lot more.

I believe the fastest rate at which the DS18B20 can return data is about once a second. This is because it essentially talks in plain english while the PT100 is just a resistor and therefore can be read faster.

While the DS18B20 can be had in a waterproof capsule, I have never seen one sensibly usable in a high pressure fitting.  The PT100s I have are are a common type, being 1/4" BSP  screw-in devices and are OK for use wet in mains-pressure water service.

Against this, the PT100 usually costs more and  involves more peripheral electronics.


k4ktus

Since now I'm used many DS18B20 but at the end I was never happy, because it is just to fragile. Meanwhile there is an cheap 22bit AD from Microchip out. With it you may just buy two additional resistors and you have a much better circuit with a range from -200°C ... 800°C with about 0.1°C deviation.

http://forum.arduino.cc/index.php?topic=164643.msg1229078#msg1229078
my blog and projects:
http://simons-holzvergaser.blogspot.com/

jubal harshaw


Yay, my sensor (finally!) arrived (that's what you get from ordering overseas via ebay...), and I got to play with it. I connected it straight to the analog pin of my arduino (well, "straight", I of course made a voltage divider for it, otherwise it wouldn't much make sense..) and run a program to read the values - and it worked!


Just to make sure, you connected it as one would connect any other thermistor? Care to post a sketch of what worked for you as a reference?

TIA,

MikeLuo

AnttiV:
Do you mind share your code and circuit with me?, I am trying to to use pt100 in between -40C ~ 400C.

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