Pt100 and esp32

Need Help With My Project
1

Dear
I wanted to ask you the following, a while ago I made a device with blynk and a nodemcu ESP8266 the interface to connect a PT100 industrial sensor, because the sensor works resistively, and is powered with 24V, I connected it to port A0 through of a bridge formed by a 220ohm resistor (connecting on side A the negative output of PT100 and A0, and on side B -24V of the source and GND. Then with a digital sensor I simultaneously measured the temperature and the values from the PT100, and I made an interpolation. I then used this interpolation in an Arduino code to read the data from the PT100 with BLYNK. It works quite well. A0 is 8 bits, I have interpolated values ​​from 0 to 1024.
The problem is that I need to do the same with the ESP32, but in principle in addition to using a different scale from the ADC 0 to 4095, with several resistors I have tried and the results are not fixed like the esp8266, but vary, it seems prone to noise , and I have also read that it must be closed. I would like to know if anyone has any ideas to make it work well with the PT100.
first of all, Thanks…

RUBEN MEDINA.
• Hardware model ESP32

2

First of all, you have to choose the right analog pin on the ESP32. To use it with WiFi (and therefore Blynk) it needs to one that’s connected to ADC1…

  • ADC1_CH0 (GPIO 36)
  • ADC1_CH1 (GPIO 37)
  • ADC1_CH2 (GPIO 38)
  • ADC1_CH3 (GPIO 39)
  • ADC1_CH4 (GPIO 32)
  • ADC1_CH5 (GPIO 33)
  • ADC1_CH6 (GPIO 34)
  • ADC1_CH7 (GPIO 35)

You can change the resolution to 0-1024 (which is actually 10 bit resolution) or use the default 12 bit resolution of 0-4095.
You can also set the attenuation too, but you might need to modify your voltage divider to get useable results.
The ESP8266 has an analog input voltage range of 0-3.3v and even with maximum attenuation the ESP32 has an analog input range of 0-2.6v

ESP32 Analog Input with Arduino IDE | Random Nerd Tutorials.

Pete.