Question

我目前正在使用Adafruit_MAX31855 IC和K型热电偶。出于某种原因，我在串行监视器中得到这个......

Internal Temp = 32.44
nan // printed from thermocouple.readCelcius()
Internal Temp = 32.44
nan
Internal Temp = 32.44
nan
Internal Temp = 32.44
nan
Internal Temp = 32.38
nan
Internal Temp = 32.38
nan
Internal Temp = 32.38
nan
Internal Temp = 32.38
nan
Internal Temp = 32.31

现在我知道所有接线都正确，因为我正在获得内部温度。除此之外，.readCelcius（）命令有时会返回正确的读数。我一开始认为最大温度可能超出了芯片的性能，但是当在40摄氏度下运行时，我有时会得到这个。

#include <SPI.h>
#include "Adafruit_MAX31855.h"

int HeaterPWM = 12;
int LEDPin = 13;
long _startTime;
long _currentTime;

#define MAXDO   3
#define MAXCS   4
#define MAXCLK  5

Adafruit_MAX31855 thermocouple(MAXCLK, MAXCS, MAXDO);


void setup() {
  while (!Serial); // wait for Serial on Leonardo/Zero, etc

  Serial.begin(9600);
  pinMode(HeaterPWM, OUTPUT);
  pinMode(LEDPin, OUTPUT);

  Serial.println("MAX31855 test");
  // wait for MAX chip to stabilize
  delay(500);
}

void loop() {

  _startTime = millis();
  while (_currentTime - _startTime < 3000) // heater on for 3 seconds at a time
  {
    Serial.print("Internal Temp = ");
    Serial.println(thermocouple.readInternal());

    _currentTime = millis();
    analogWrite(HeaterPWM, 150);
    digitalWrite(LEDPin, HIGH);
    double c = sampleCelcius(1);
    Serial.println(c);
    delay(10);
  }

  _startTime = millis();

  while (_currentTime - _startTime < 10000) // heater on for 3 seconds at a time
  {
    Serial.print("Internal Temp = ");
    Serial.println(thermocouple.readInternal());

    _currentTime = millis();
    analogWrite(HeaterPWM, 0);
    digitalWrite(LEDPin, LOW);
    double c = sampleCelcius(1);
    Serial.println(c);
    delay(10);
  }
}

double sampleCelcius(int maxSamples)
{
  double result = NAN;
  for (int i = 0; i < maxSamples; i++)
  {
    result = thermocouple.readCelsius();
    if (!isnan(result)) // exit on first good reading.
      break;
    delay(10);
  }
  return result;
}

我检查了所有电压和PWM输出等，以及对热电偶进行基准测试。当它在室温下工作时是正确的。当加热器打开时，我确实得到了读数而不是楠，我似乎得到了数以千计的非常高的数字，这显然是不正确的。它应该在65摄氏度左右。

有什么想法吗？

Answer 1

事实证明，Adafruit_MAX31855 IC与导电表面不兼容，“加热”也会向热电偶发送电压，从而丢失读数。

Adafruit_MAX31855 Thermopile IC readcelcius（）命令返回nan

1 个答案: