SHT31 negative temp issue

Other Hardware Sensors
1

Hello,

I have an issue with a SHT31-D and wemos D1 mini pro. It's done for -40°C - +65°C.
I use the code below, but I have an issue when temperature is negative.
I got value : 42949672.0°C instead of negative value. For positive value, no problem !
Humidity is fine even temp is negative.
Do I miss something ? Is there any tips.

#include <Arduino.h>
#include <Wire.h>
#include "Adafruit_SHT31.h"

Adafruit_SHT31 sht31 = Adafruit_SHT31();

void setup() {
  Serial.begin(9600);

  while (!Serial)
    delay(10);     // will pause Zero, Leonardo, etc until serial console opens

  Serial.println("SHT31 test");
  if (! sht31.begin(0x44)) {   // Set to 0x45 for alternate i2c addr
    Serial.println("Couldn't find SHT31");
    while (1) delay(1);
  }
}


void loop() {
  float t = sht31.readTemperature();
  float h = sht31.readHumidity();
  Serial.print("Temp *C = "); Serial.println(t);
  Serial.print("Hum. % = "); Serial.println(h);
  delay(1000);
}

thanks in advance

2

Have a look into the Adadfruit SHT31 library (Adafruit_SHT31.cpp).

 uint32_t stemp = ((uint32_t)readbuffer[0] << 8) | readbuffer[1];
  // simplified (65536 instead of 65535) integer version of:
  //temp = (stemp * 175.0f) / 65535.0f - 45.0f;
  stemp = ((4375 * stemp) >> 14) - 4500;
  temp = (float) stemp / 100.0f;

Try the version they have commented out and comment the last two lines. Maybe there is an issue with the conversion in the "simplified" version.

3

Hi Klaus,

thanks for your feedback, I have found solution.
After checking my amazon order and sensor specs, it appears that model SHT31-D cannot run under zero (Humidity)
The model SHT31-A can do it ...

So for my weather station, it's a little problem ::slight_smile:
I have replaced this sensor y DHT22 ... and that works.

Case can be closed