user52814: I am using PT100 (3 Wire) to measure the temperature with Arduino Uno and MAX31865. 
I have connected everything perfectly.
Configuration in the code i am using is :
max1.begin(MAX31865_3WIRE);

And the output is:
output
RTD value: 0 
Ratio = 0.00000000
Resistance = 0.00000000
Temperature = -242.02

I am testing it in a room temperature.
My question is , is there any settings or calibration that i need to do, or any other way to test the PT100 sensor, because the temperature is showing correct readings ?

user57061: I nearly have the same problem. I use five of the MAX31865-Boards with 2-Wire Termocouples on an Arduino Nano. Two of the five boards are working perfectly. The other 3 boards show exactly the same wrong behaviour you described. My temperature readings are exactly like yours (-242.02).
But I think I found the reason for the not working ones: The two working boards I bought on Amazon. The other three not working boards I bought on AliExpress. Maybe I (and maybe you too) got really bad fakes from China and they are simply dead :(
(BTW: If I remove one working board from the SPI bus and read out the temperature with the arduino, I get also the value of -242.02. This value seems to be an error value in the Adafruit MAX31865 library)
EDIT: Fixed it with a workaround!Like shown in the picture below, simply remove the wrong component (SMD Capacitor) and create a solder bridge . See comments for more informations!
Here is a picture of my modification of one chinese board as requested by the comments:

(It's not the best solution, but it works. For final using you should get the right filter ferrite and solder it on the board!)

52814: <p>I am using PT100 (3 Wire) to measure the temperature with Arduino Uno and MAX31865. 
I have connected everything perfectly.
Configuration in the code i am using is :</p>

<pre><code>max1.begin(MAX31865_3WIRE);
</code></pre>

<p>And the output is:</p>

<p><strong>output</strong></p>

<pre><code>RTD value: 0 
Ratio = 0.00000000
Resistance = 0.00000000
Temperature = -242.02
</code></pre>

<p>I am testing it in a room temperature.</p>

<p>My question is , is there any settings or calibration that i need to do, or any other way to test the PT100 sensor, because the temperature is showing correct readings ?</p>
 57061: <p>I nearly have the same problem. I use five of the MAX31865-Boards with 2-Wire Termocouples on an Arduino Nano. Two of the five boards are working perfectly. The other 3 boards show exactly the same wrong behaviour you described. My temperature readings are exactly like yours (-242.02).</p>

<p>But I think I found the reason for the not working ones: The two working boards I bought on Amazon. The other three not working boards I bought on AliExpress. Maybe I (and maybe you too) got really bad fakes from China and they are simply dead :(</p>

<p><em>(BTW: If I remove one working board from the SPI bus and read out the temperature with the arduino, I get also the value of -242.02. This value seems to be an error value in the Adafruit MAX31865 library)</em></p>

<p><strong>EDIT: Fixed it with a workaround!Like shown in the picture below, simply remove the wrong component (SMD Capacitor) and create a solder bridge . See comments for more informations!</strong></p>

<p>Here is a picture of my modification of one chinese board as requested by the comments:</p>

<p><a href="https://i.stack.imgur.com/aD02L.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aD02L.jpg" alt="Modification of the chinese MAX31865 driver board"></a></p>

<p>(It's not the best solution, but it works. For final using you should get the right filter ferrite and solder it on the board!)</p>
