Hi all,
The issue: The temperature log displays temperatures which are a few degrees to high. For example boiling water has around 103 °C, cooled water with ice cubes around 6 °C, room temperature around 28 °C instead of 24 °C. So it is pretty close, but somewhat a few degrees too high.
I have tested another PT1000 from a different vendor, same issue.
Any ideas what is wrong here?
The log looks like this:
RTD value: 8460
Ratio = 0.25817871
Resistance = 1110.16845703
Temperature = 28.31
I am using:
- ESP32 development board (https://www.berrybase.de/esp32-nodemcu-development-board)
- PT1000 Class AA, 4 cable (black/white: + + ; yellow/red: - -)
- MAX31865 with RREF 432
Connection:
ESP32 --> MAX31865
GND --> GND
3V3 --> 3V3
G5 --> CS
G18 --> CLK
G19 --> SDO
G23 --> SDI
I use this code:
/***************************************************
This is a library for the Adafruit PT100/P1000 RTD Sensor w/MAX31865
Designed specifically to work with the Adafruit RTD Sensor
----> https://www.adafruit.com/products/3328
This sensor uses SPI to communicate, 4 pins are required to
interface
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!
Written by Limor Fried/Ladyada for Adafruit Industries.
BSD license, all text above must be included in any redistribution
****************************************************/
#include <Adafruit_MAX31865.h>
// Use software SPI: CS, DI, DO, CLK
Adafruit_MAX31865 thermo = Adafruit_MAX31865(5, 23, 19, 18);
//Adafruit_MAX31865 thermo = Adafruit_MAX31865(10, 11, 12, 13);
//Adafruit_MAX31865 max = Adafruit_MAX31865(5, 23, 19, 18);
// use hardware SPI, just pass in the CS pin
//Adafruit_MAX31865 thermo = Adafruit_MAX31865(10);
// The value of the Rref resistor. Use 430.0 for PT100 and 4300.0 for PT1000
#define RREF 4300.0
// The 'nominal' 0-degrees-C resistance of the sensor
// 100.0 for PT100, 1000.0 for PT1000
#define RNOMINAL 1000.0
void setup() {
Serial.begin(115200);
Serial.println("Adafruit MAX31865 PT100 Sensor Test!");
thermo.begin(MAX31865_4WIRE); // set to 2WIRE or 4WIRE as necessary
}
void loop() {
uint16_t rtd = thermo.readRTD();
Serial.print("RTD value: "); Serial.println(rtd);
float ratio = rtd;
ratio /= 32768;
Serial.print("Ratio = "); Serial.println(ratio,8);
Serial.print("Resistance = "); Serial.println(RREF*ratio,8);
Serial.print("Temperature = "); Serial.println(thermo.temperature(RNOMINAL, RREF));
// Check and print any faults
uint8_t fault = thermo.readFault();
if (fault) {
Serial.print("Fault 0x"); Serial.println(fault, HEX);
if (fault & MAX31865_FAULT_HIGHTHRESH) {
Serial.println("RTD High Threshold");
}
if (fault & MAX31865_FAULT_LOWTHRESH) {
Serial.println("RTD Low Threshold");
}
if (fault & MAX31865_FAULT_REFINLOW) {
Serial.println("REFIN- > 0.85 x Bias");
}
if (fault & MAX31865_FAULT_REFINHIGH) {
Serial.println("REFIN- < 0.85 x Bias - FORCE- open");
}
if (fault & MAX31865_FAULT_RTDINLOW) {
Serial.println("RTDIN- < 0.85 x Bias - FORCE- open");
}
if (fault & MAX31865_FAULT_OVUV) {
Serial.println("Under/Over voltage");
}
thermo.clearFault();
}
Serial.println();
delay(1000);
}
I have added some pictures as well.
