Some opinions on Arduino-PT100-TLK31-RS458 project

[redoomed]

Hello,

There's a project that i have to make and i would like to know your opinion on some problems that exist.
One part of the project (I will not bother you with the rest since there's no need) is that I need to take a value from the PT100 temprature sensor (RTD 3 wires) and send it to Arduino. However the PT100 is already conected to a TLK 31. This is a microcontroller with Display that shows the temprature value from the PT100.
I want to take this PT100 value to Arduino without bothering the PT100 - TLK 31 connection.
I also noticed (in the datasheet) that 3 pins of the TLK 31 is dedicated for RS485 connection.

So, Ι come to the substance:
How can I get the PT100 value to Arduino? Do I have to use RS485 pins from TLK 31 maybe with a RS485 module for Arduino to send the data from TLK31 to Arduino?
Can I just connect some wires simple on the PT100 to take the value?
I saw that RTDs sensors (like PT100) may need a kind of circuit before the Arduino input pin (bridge, op-amps). But if I use this kind of circuit on the connection of PT100 with TLK 31 won't I go bad the TLK 31's measurement?

I'm in the very start of the project so every opinion, idea, suggestion would be more than useful.
Whoever has some knowledge on this topic, it would be very nice to share it.
Thanks for reading my topic, I'm looking forward to see your opinions.
Good afternoon

 

[andre_luis]

Any measurement in the analogue domain implicitly carries a certain degree of inaccuracy, so that performing a measurement in parallel with the equipment itself although in principle would not add any significant load effect, the suspended wirings could get noise by induction. In this case, I believe that reading the serial connection would be the most appropriate decision.

 

[KlausST]

Hi,

if you expect to read the PT100 analog value in parallle with the TLK, then you need to know how the PT 100 is driven:
* constant voltage (with resistor)
* constant current
* Ratiometric with power supply
* ...

Klaus

 

[redoomed]

KlausST you mean something like the figure 2 on this link: https://www.maximintegrated.com/en/app-notes/index.mvp/id/3450 ?

andre_teprom the problem is that i do not have any experience on RS485 and i don't know what/how to do it.

 

[andre_luis]

the problem is that i do not have any experience on RS485 and i don't know what/how to do it.

The RS485 standard defines only the electrical specifications of the physical layer.
If you already work with UART, there is nothing new to learn.