Strange data from MCP9808 High Accuracy I2C Temperature sens

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billf
 
Posts: 51
Joined: Mon Jun 20, 2011 9:58 am

Strange data from MCP9808 High Accuracy I2C Temperature sens

Post by billf »

I was testing out the MCP9808 High Accuracy I2C Temperature Sensor Breakout Board (PID 1782) and I got some strange data when the temperature went below 0 degrees Celsius. I had the sensor in my freezer (my environmental test chamber) and I was watching the temperature output in the Serial window. I have cut and pasted that data here to illustrate what happened when the temperature of the sensor went below 0 degrees Celsius,

Code: Select all

Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.37*C	32.68*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.25*C	32.45*F
Temp: 0.19*C	32.34*F
Temp: 0.25*C	32.45*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: -255.94*C	-428.69*F
Temp: 0.00*C	32.00*F
Temp: -255.94*C	-428.69*F
Temp: -255.94*C	-428.69*F
Temp: -255.88*C	-428.58*F
Temp: -255.94*C	-428.69*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.94*C	-428.69*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.88*C	-428.58*F
Temp: -255.81*C	-428.46*F
Temp: -255.81*C	-428.46*F
Temp: -255.81*C	-428.46*F
Temp: -255.88*C	-428.58*F
Temp: -255.81*C	-428.46*F
Temp: -255.81*C	-428.46*F
Temp: -255.75*C	-428.35*F
Temp: -255.81*C	-428.46*F
Temp: -255.75*C	-428.35*F
Temp: -255.81*C	-428.46*F
Temp: -255.81*C	-428.46*F
Temp: -255.81*C	-428.46*F
Temp: -255.75*C	-428.35*F
Temp: -255.75*C	-428.35*F
Temp: -255.81*C	-428.46*F
Temp: -255.75*C	-428.35*F
Temp: -255.81*C	-428.46*F
Temp: -255.69*C	-428.24*F
Temp: -255.69*C	-428.24*F
Temp: -255.69*C	-428.24*F
Temp: -255.69*C	-428.24*F
Temp: -255.69*C	-428.24*F
Temp: -255.69*C	-428.24*F
Temp: -255.75*C	-428.35*F
Temp: -255.63*C	-428.13*F
Temp: -255.69*C	-428.24*F
Temp: -255.69*C	-428.24*F
Temp: -255.63*C	-428.13*F
Temp: -255.63*C	-428.13*F
Temp: -255.69*C	-428.24*F
Temp: -255.56*C	-428.01*F
Temp: -255.63*C	-428.13*F
Temp: -255.56*C	-428.01*F
Temp: -255.63*C	-428.13*F
Temp: -255.56*C	-428.01*F
Temp: -255.63*C	-428.13*F
Temp: -255.56*C	-428.01*F
Temp: -255.56*C	-428.01*F
Temp: -255.56*C	-428.01*F
Temp: -255.56*C	-428.01*F
Temp: -255.56*C	-428.01*F
Temp: -255.50*C	-427.90*F
Temp: -255.56*C	-428.01*F
Temp: -255.50*C	-427.90*F
Temp: -255.56*C	-428.01*F
Temp: -255.50*C	-427.90*F
Temp: -255.50*C	-427.90*F
Temp: -255.50*C	-427.90*F
Temp: -255.44*C	-427.79*F
Temp: -255.44*C	-427.79*F
Temp: -255.56*C	-428.01*F
Temp: -255.38*C	-427.67*F
Temp: -255.44*C	-427.79*F
Temp: -255.50*C	-427.90*F
Temp: -255.38*C	-427.67*F
Temp: -255.44*C	-427.79*F
Temp: -255.44*C	-427.79*F
Temp: -255.31*C	-427.56*F
Temp: -255.38*C	-427.67*F
Temp: -255.38*C	-427.67*F
Temp: -255.38*C	-427.67*F
Temp: -255.38*C	-427.67*F
Temp: -255.38*C	-427.67*F
Temp: -255.31*C	-427.56*F
Temp: -255.31*C	-427.56*F
Temp: -255.25*C	-427.45*F
Temp: -255.25*C	-427.45*F
Temp: -255.31*C	-427.56*F
Temp: -255.31*C	-427.56*F
Temp: -255.31*C	-427.56*F
Temp: -255.31*C	-427.56*F
Temp: -255.25*C	-427.45*F
Temp: -255.25*C	-427.45*F
Temp: -255.25*C	-427.45*F
Temp: -255.25*C	-427.45*F
Temp: -255.25*C	-427.45*F
Temp: -255.19*C	-427.34*F
Temp: -255.19*C	-427.34*F
Temp: -255.25*C	-427.45*F
Temp: -255.19*C	-427.34*F
Temp: -255.19*C	-427.34*F
Temp: -255.19*C	-427.34*F
Temp: -255.13*C	-427.23*F
Temp: -255.13*C	-427.23*F
Temp: -255.06*C	-427.11*F
Temp: -255.19*C	-427.34*F
Temp: -255.13*C	-427.23*F
Temp: -255.13*C	-427.23*F
Temp: -255.06*C	-427.11*F
Temp: -255.13*C	-427.23*F
Temp: -255.13*C	-427.23*F
Temp: -255.13*C	-427.23*F
Temp: -255.13*C	-427.23*F
Temp: -255.06*C	-427.11*F
Temp: -255.06*C	-427.11*F
Temp: -255.00*C	-427.00*F
Temp: -255.00*C	-427.00*F
Temp: -255.06*C	-427.11*F
Temp: -254.94*C	-426.89*F
Temp: -255.06*C	-427.11*F
Temp: -255.00*C	-427.00*F
Temp: -255.00*C	-427.00*F
Temp: -255.00*C	-427.00*F
Temp: -255.00*C	-427.00*F
Temp: -254.94*C	-426.89*F
Temp: -255.00*C	-427.00*F
Temp: -254.94*C	-426.89*F
Temp: -254.94*C	-426.89*F
Temp: -254.94*C	-426.89*F
Temp: -254.94*C	-426.89*F
Temp: -254.94*C	-426.89*F
Temp: -254.88*C	-426.77*F
Temp: -254.88*C	-426.77*F
Temp: -254.88*C	-426.77*F
Temp: -254.88*C	-426.77*F
Temp: -254.88*C	-426.77*F
Temp: -254.88*C	-426.77*F
Temp: -254.88*C	-426.77*F
Temp: -254.81*C	-426.66*F
Temp: -254.81*C	-426.66*F         // I took it out of the freezer somewhere around here 
Temp: -254.88*C	-426.77*F
Temp: -255.00*C	-427.00*F
Temp: -255.13*C	-427.23*F
Temp: -255.25*C	-427.45*F
Temp: -255.31*C	-427.56*F
Temp: -255.31*C	-427.56*F
Temp: -255.38*C	-427.67*F
Temp: -255.31*C	-427.56*F
Temp: -255.31*C	-427.56*F
Temp: -255.31*C	-427.56*F
Temp: -255.38*C	-427.67*F
Temp: -255.50*C	-427.90*F
Temp: -255.56*C	-428.01*F
Temp: -255.63*C	-428.13*F
Temp: -255.75*C	-428.35*F
Temp: -255.75*C	-428.35*F
Temp: -255.94*C	-428.69*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.06*C	32.11*F
Temp: 0.19*C	32.34*F
Temp: 0.25*C	32.45*F
Temp: 0.31*C	32.56*F
Temp: 0.25*C	32.45*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.44*C	32.79*F
Temp: 0.37*C	32.68*F
Temp: 0.44*C	32.79*F
Temp: 0.56*C	33.01*F
Temp: 0.56*C	33.01*F
Temp: 0.63*C	33.13*F
Temp: 0.56*C	33.01*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.75*C	33.35*F
Temp: 0.81*C	33.46*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.06*C	33.91*F
Temp: 1.06*C	33.91*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.25*C	34.25*F
Temp: 1.31*C	34.36*F
Temp: 1.25*C	34.25*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.50*C	34.70*F
Temp: 1.44*C	34.59*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.69*C	35.04*F
Temp: 1.75*C	35.15*F
Temp: 1.69*C	35.04*F
Temp: 1.75*C	35.15*F
Temp: 1.75*C	35.15*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F


Any idea why this would happen? I think the spec says it should work down to -40 degrees Celsius.

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adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by adafruit_support_mike »

That's probably a data representation issue in the code. Post the part that collects the variable and prints it, and we'll see what we can find.

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billf
 
Posts: 51
Joined: Mon Jun 20, 2011 9:58 am

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by billf »

Excuse me if I have included too much code below, but I did not want to exclude a variable definition in case that was a problem.

Code: Select all

/**************************************************************************/
/*!
This is a demo for the Adafruit MCP9808 breakout
----> http://www.adafruit.com/products/1782
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!
*/
/**************************************************************************/

#include <Wire.h>
#include "Adafruit_MCP9808.h"

// Create the MCP9808 temperature sensor object
Adafruit_MCP9808 tempsensor = Adafruit_MCP9808();

void setup() {
  Serial.begin(9600);
  Serial.println("MCP9808 demo");
  
  // Make sure the sensor is found, you can also pass in a different i2c
  // address with tempsensor.begin(0x19) for example
  if (!tempsensor.begin()) {
    Serial.println("Couldn't find MCP9808!");
    while (1);
  }
}

void loop() {
  // Read and print out the temperature, then convert to *F
  float c = tempsensor.readTempC();
  float f = c * 9.0 / 5.0 + 32;
  Serial.print("Temp: "); Serial.print(c); Serial.print("*C\t"); 
  Serial.print(f); Serial.println("*F");
  delay(250);
}

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adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by adafruit_support_mike »

Posting the full code is always good. ;-)

I think you may have uncovered a glitch in the library. The MCP9808 has a 12-bit ADC that represents negative numbers in twos-complement notation. The library function that reads the temperature doesn't seem to decode that when it gets a negative temperature.

Open the file MCP9808.cpp and replace line 74:

Code: Select all

  if (t & 0x1000) temp *= -1;
with this:

Code: Select all

  if (t & 0x1000) temp = t - 0x1000;
See if that gives you the output you expect.

User avatar
adafruit2
 
Posts: 22148
Joined: Fri Mar 11, 2005 7:36 pm

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by adafruit2 »

That one-line change wont work as-is, please download the latest version of the library from
https://github.com/adafruit/Adafruit_MCP9808_Library
to try our new fix :)

User avatar
billf
 
Posts: 51
Joined: Mon Jun 20, 2011 9:58 am

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by billf »

I downloaded the new library MCP9808 and the results are different (indicating that something changed), but not correct yet.

I ran the same experiment as before and when the temperatures as shown on the Serial monitor get down to 0 degrees Celsius (32 degrees Fahrenheit), they start going UP from there, which is not what is expected because the freezer should be bringing the temperature down to around 0 degrees Fahrenheit. So I'm guessing that the Celsius temperatures may be correct in magnitude, but they represented properly as negative numbers. The degrees Fahrenheit are calculated from the value of degrees Celsius, so they are not correct either (that is not the issue here - once we get the degrees Celsius correct, the Fahrenheit should be correct).

I have cut/pasted the data from the Serial monitor below:

I did add a few " // comments " to the data to point out where I think the problems are.

Code: Select all

Temp: 6.00*C	42.80*F
Temp: 6.06*C	42.91*F
Temp: 6.00*C	42.80*F
Temp: 6.00*C	42.80*F
Temp: 6.00*C	42.80*F
Temp: 5.94*C	42.69*F
Temp: 5.94*C	42.69*F
Temp: 5.88*C	42.58*F
Temp: 5.81*C	42.46*F
Temp: 5.81*C	42.46*F
Temp: 5.81*C	42.46*F
Temp: 5.81*C	42.46*F
Temp: 5.81*C	42.46*F
Temp: 5.75*C	42.35*F
Temp: 5.75*C	42.35*F
Temp: 5.69*C	42.24*F
Temp: 5.69*C	42.24*F
Temp: 5.63*C	42.13*F
Temp: 5.63*C	42.13*F
Temp: 5.56*C	42.01*F
Temp: 5.56*C	42.01*F
Temp: 5.56*C	42.01*F
Temp: 5.50*C	41.90*F
Temp: 5.50*C	41.90*F
Temp: 5.50*C	41.90*F
Temp: 5.50*C	41.90*F
Temp: 5.38*C	41.68*F
Temp: 5.44*C	41.79*F
Temp: 5.38*C	41.68*F
Temp: 5.31*C	41.56*F
Temp: 5.31*C	41.56*F
Temp: 5.25*C	41.45*F
Temp: 5.25*C	41.45*F
Temp: 5.25*C	41.45*F
Temp: 5.31*C	41.56*F
Temp: 5.25*C	41.45*F
Temp: 5.19*C	41.34*F
Temp: 5.25*C	41.45*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.06*C	41.11*F
Temp: 5.06*C	41.11*F
Temp: 5.06*C	41.11*F
Temp: 5.06*C	41.11*F
Temp: 5.00*C	41.00*F
Temp: 5.00*C	41.00*F
Temp: 4.94*C	40.89*F
Temp: 4.94*C	40.89*F
Temp: 4.94*C	40.89*F
Temp: 4.94*C	40.89*F
Temp: 4.94*C	40.89*F
Temp: 4.88*C	40.78*F
Temp: 4.88*C	40.78*F
Temp: 4.88*C	40.78*F
Temp: 4.94*C	40.89*F
Temp: 4.94*C	40.89*F
Temp: 4.88*C	40.78*F
Temp: 4.88*C	40.78*F
Temp: 4.88*C	40.78*F
Temp: 4.81*C	40.66*F
Temp: 4.81*C	40.66*F
Temp: 4.75*C	40.55*F
Temp: 4.81*C	40.66*F
Temp: 4.69*C	40.44*F
Temp: 4.69*C	40.44*F
Temp: 4.63*C	40.33*F
Temp: 4.63*C	40.33*F
Temp: 4.63*C	40.33*F
Temp: 4.56*C	40.21*F
Temp: 4.56*C	40.21*F
Temp: 4.56*C	40.21*F
Temp: 4.56*C	40.21*F
Temp: 4.50*C	40.10*F
Temp: 4.50*C	40.10*F
Temp: 4.50*C	40.10*F
Temp: 4.44*C	39.99*F
Temp: 4.44*C	39.99*F
Temp: 4.44*C	39.99*F
Temp: 4.44*C	39.99*F
Temp: 4.38*C	39.88*F
Temp: 4.38*C	39.88*F
Temp: 4.31*C	39.76*F
Temp: 4.31*C	39.76*F
Temp: 4.25*C	39.65*F
Temp: 4.25*C	39.65*F
Temp: 4.25*C	39.65*F
Temp: 4.19*C	39.54*F
Temp: 4.13*C	39.43*F
Temp: 4.13*C	39.43*F
Temp: 4.13*C	39.43*F
Temp: 4.13*C	39.43*F
Temp: 4.06*C	39.31*F
Temp: 4.06*C	39.31*F
Temp: 4.00*C	39.20*F
Temp: 4.06*C	39.31*F
Temp: 4.00*C	39.20*F
Temp: 4.06*C	39.31*F
Temp: 4.00*C	39.20*F
Temp: 3.94*C	39.09*F
Temp: 3.94*C	39.09*F
Temp: 3.88*C	38.97*F
Temp: 3.94*C	39.09*F
Temp: 3.88*C	38.97*F
Temp: 3.88*C	38.97*F
Temp: 3.75*C	38.75*F
Temp: 3.75*C	38.75*F
Temp: 3.75*C	38.75*F
Temp: 3.75*C	38.75*F
Temp: 3.69*C	38.64*F
Temp: 3.63*C	38.53*F
Temp: 3.63*C	38.53*F
Temp: 3.63*C	38.53*F
Temp: 3.56*C	38.41*F
Temp: 3.56*C	38.41*F
Temp: 3.56*C	38.41*F
Temp: 3.56*C	38.41*F
Temp: 3.50*C	38.30*F
Temp: 3.56*C	38.41*F
Temp: 3.50*C	38.30*F
Temp: 3.44*C	38.19*F
Temp: 3.50*C	38.30*F
Temp: 3.44*C	38.19*F
Temp: 3.44*C	38.19*F
Temp: 3.38*C	38.08*F
Temp: 3.38*C	38.08*F
Temp: 3.38*C	38.08*F
Temp: 3.31*C	37.96*F
Temp: 3.31*C	37.96*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.19*C	37.74*F
Temp: 3.19*C	37.74*F
Temp: 3.19*C	37.74*F
Temp: 3.19*C	37.74*F
Temp: 3.13*C	37.63*F
Temp: 3.13*C	37.63*F
Temp: 3.13*C	37.63*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.75*C	36.95*F
Temp: 2.75*C	36.95*F
Temp: 2.69*C	36.84*F
Temp: 2.75*C	36.95*F
Temp: 2.69*C	36.84*F
Temp: 2.63*C	36.72*F
Temp: 2.69*C	36.84*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.56*C	36.61*F
Temp: 2.50*C	36.50*F
Temp: 2.50*C	36.50*F
Temp: 2.50*C	36.50*F
Temp: 2.50*C	36.50*F
Temp: 2.44*C	36.39*F
Temp: 2.44*C	36.39*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.44*C	36.39*F
Temp: 2.31*C	36.16*F
Temp: 2.38*C	36.28*F
Temp: 2.31*C	36.16*F
Temp: 2.38*C	36.28*F
Temp: 2.25*C	36.05*F
Temp: 2.31*C	36.16*F
Temp: 2.25*C	36.05*F
Temp: 2.25*C	36.05*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.13*C	35.83*F
Temp: 2.19*C	35.94*F
Temp: 2.13*C	35.83*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.06*C	35.71*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 1.88*C	35.38*F
Temp: 1.94*C	35.49*F
Temp: 1.88*C	35.38*F
Temp: 1.81*C	35.26*F
Temp: 1.88*C	35.38*F
Temp: 1.81*C	35.26*F
Temp: 1.75*C	35.15*F
Temp: 1.75*C	35.15*F
Temp: 1.81*C	35.26*F
Temp: 1.69*C	35.04*F
Temp: 1.75*C	35.15*F
Temp: 1.69*C	35.04*F
Temp: 1.69*C	35.04*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.06*C	33.91*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.06*C	33.91*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.06*C	33.91*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.81*C	33.46*F
Temp: 0.81*C	33.46*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.56*C	33.01*F
Temp: 0.56*C	33.01*F
Temp: 0.63*C	33.13*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.56*C	33.01*F
Temp: 0.50*C	32.90*F
Temp: 0.44*C	32.79*F
Temp: 0.50*C	32.90*F
Temp: 0.44*C	32.79*F
Temp: 0.44*C	32.79*F
Temp: 0.37*C	32.68*F
Temp: 0.44*C	32.79*F
Temp: 0.37*C	32.68*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.19*C	32.34*F
Temp: 0.25*C	32.45*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.00*C	32.00*F
Temp: 0.06*C	32.11*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.06*C	32.11*F                 // I think this should be NEGATIVE Celsius degrees - starting here
Temp: 0.00*C	32.00*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.25*C	32.45*F
Temp: 0.19*C	32.34*F
Temp: 0.25*C	32.45*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.31*C	32.56*F
Temp: 0.44*C	32.79*F
Temp: 0.44*C	32.79*F
Temp: 0.50*C	32.90*F
Temp: 0.44*C	32.79*F
Temp: 0.44*C	32.79*F
Temp: 0.56*C	33.01*F
Temp: 0.50*C	32.90*F
Temp: 0.56*C	33.01*F
Temp: 0.50*C	32.90*F
Temp: 0.56*C	33.01*F
Temp: 0.56*C	33.01*F
Temp: 0.56*C	33.01*F
Temp: 0.69*C	33.24*F
Temp: 0.63*C	33.13*F
Temp: 0.69*C	33.24*F
Temp: 0.69*C	33.24*F
Temp: 0.69*C	33.24*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.81*C	33.46*F
Temp: 0.81*C	33.46*F
Temp: 0.81*C	33.46*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.81*C	33.46*F
Temp: 0.88*C	33.58*F
Temp: 0.94*C	33.69*F
Temp: 0.88*C	33.58*F
Temp: 0.94*C	33.69*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.06*C	33.91*F
Temp: 1.00*C	33.80*F
Temp: 1.06*C	33.91*F
Temp: 1.06*C	33.91*F
Temp: 1.06*C	33.91*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.31*C	34.36*F
Temp: 1.25*C	34.25*F
Temp: 1.31*C	34.36*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.44*C	34.59*F
Temp: 1.44*C	34.59*F
Temp: 1.44*C	34.59*F
Temp: 1.44*C	34.59*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.63*C	34.93*F
Temp: 1.56*C	34.81*F
Temp: 1.69*C	35.04*F
Temp: 1.69*C	35.04*F
Temp: 1.75*C	35.15*F
Temp: 1.69*C	35.04*F
Temp: 1.69*C	35.04*F
Temp: 1.75*C	35.15*F
Temp: 1.75*C	35.15*F
Temp: 1.75*C	35.15*F
Temp: 1.75*C	35.15*F
Temp: 1.81*C	35.26*F
Temp: 1.81*C	35.26*F
Temp: 1.81*C	35.26*F
Temp: 1.81*C	35.26*F
Temp: 1.81*C	35.26*F
Temp: 1.81*C	35.26*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.19*C	35.94*F
Temp: 2.19*C	35.94*F
Temp: 2.19*C	35.94*F
Temp: 2.19*C	35.94*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.31*C	36.16*F
Temp: 2.25*C	36.05*F
Temp: 2.25*C	36.05*F
Temp: 2.31*C	36.16*F
Temp: 2.38*C	36.28*F
Temp: 2.25*C	36.05*F
Temp: 2.31*C	36.16*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.44*C	36.39*F
Temp: 2.44*C	36.39*F
Temp: 2.44*C	36.39*F
Temp: 2.50*C	36.50*F
Temp: 2.50*C	36.50*F
Temp: 2.50*C	36.50*F
Temp: 2.50*C	36.50*F
Temp: 2.56*C	36.61*F
Temp: 2.50*C	36.50*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.63*C	36.72*F
Temp: 2.56*C	36.61*F
Temp: 2.69*C	36.84*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.69*C	36.84*F
Temp: 2.69*C	36.84*F
Temp: 2.69*C	36.84*F
Temp: 2.75*C	36.95*F
Temp: 2.75*C	36.95*F
Temp: 2.75*C	36.95*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 2.88*C	37.18*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 3.06*C	37.51*F
Temp: 3.00*C	37.40*F
Temp: 3.06*C	37.51*F
Temp: 3.13*C	37.63*F
Temp: 3.06*C	37.51*F
Temp: 3.13*C	37.63*F
Temp: 3.13*C	37.63*F
Temp: 3.13*C	37.63*F
Temp: 3.19*C	37.74*F
Temp: 3.19*C	37.74*F
Temp: 3.19*C	37.74*F
Temp: 3.19*C	37.74*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.31*C	37.96*F
Temp: 3.25*C	37.85*F
Temp: 3.31*C	37.96*F
Temp: 3.31*C	37.96*F
Temp: 3.31*C	37.96*F
Temp: 3.31*C	37.96*F
Temp: 3.38*C	38.08*F
Temp: 3.44*C	38.19*F
Temp: 3.44*C	38.19*F
Temp: 3.44*C	38.19*F
Temp: 3.44*C	38.19*F
Temp: 3.50*C	38.30*F
Temp: 3.50*C	38.30*F
Temp: 3.50*C	38.30*F
Temp: 3.44*C	38.19*F
Temp: 3.56*C	38.41*F
Temp: 3.50*C	38.30*F
Temp: 3.56*C	38.41*F
Temp: 3.56*C	38.41*F
Temp: 3.56*C	38.41*F
Temp: 3.63*C	38.53*F
Temp: 3.63*C	38.53*F
Temp: 3.63*C	38.53*F
Temp: 3.69*C	38.64*F
Temp: 3.63*C	38.53*F
Temp: 3.63*C	38.53*F
Temp: 3.69*C	38.64*F
Temp: 3.69*C	38.64*F
Temp: 3.69*C	38.64*F
Temp: 3.75*C	38.75*F
Temp: 3.75*C	38.75*F
Temp: 3.75*C	38.75*F
Temp: 3.75*C	38.75*F
Temp: 3.81*C	38.86*F
Temp: 3.81*C	38.86*F
Temp: 3.88*C	38.97*F
Temp: 3.81*C	38.86*F
Temp: 3.88*C	38.97*F
Temp: 3.81*C	38.86*F
Temp: 3.88*C	38.97*F
Temp: 3.94*C	39.09*F
Temp: 3.88*C	38.97*F
Temp: 3.88*C	38.97*F
Temp: 3.94*C	39.09*F
Temp: 3.94*C	39.09*F
Temp: 4.00*C	39.20*F
Temp: 3.94*C	39.09*F
Temp: 4.00*C	39.20*F
Temp: 4.06*C	39.31*F
Temp: 4.06*C	39.31*F
Temp: 4.00*C	39.20*F
Temp: 4.06*C	39.31*F
Temp: 4.06*C	39.31*F
Temp: 4.06*C	39.31*F
Temp: 4.06*C	39.31*F
Temp: 4.06*C	39.31*F
Temp: 4.13*C	39.43*F
Temp: 4.06*C	39.31*F
Temp: 4.13*C	39.43*F
Temp: 4.13*C	39.43*F
Temp: 4.06*C	39.31*F
Temp: 4.06*C	39.31*F
Temp: 4.06*C	39.31*F
Temp: 4.13*C	39.43*F
Temp: 4.13*C	39.43*F
Temp: 4.06*C	39.31*F
Temp: 4.13*C	39.43*F
Temp: 4.13*C	39.43*F
Temp: 4.13*C	39.43*F
Temp: 4.19*C	39.54*F
Temp: 4.13*C	39.43*F
Temp: 4.25*C	39.65*F
Temp: 4.13*C	39.43*F
Temp: 4.19*C	39.54*F
Temp: 4.25*C	39.65*F
Temp: 4.19*C	39.54*F
Temp: 4.25*C	39.65*F
Temp: 4.25*C	39.65*F
Temp: 4.25*C	39.65*F
Temp: 4.31*C	39.76*F
Temp: 4.25*C	39.65*F
Temp: 4.31*C	39.76*F
Temp: 4.31*C	39.76*F
Temp: 4.25*C	39.65*F
Temp: 4.31*C	39.76*F
Temp: 4.31*C	39.76*F
Temp: 4.38*C	39.88*F
Temp: 4.38*C	39.88*F
Temp: 4.38*C	39.88*F
Temp: 4.38*C	39.88*F
Temp: 4.38*C	39.88*F
Temp: 4.44*C	39.99*F
Temp: 4.44*C	39.99*F
Temp: 4.44*C	39.99*F
Temp: 4.50*C	40.10*F
Temp: 4.50*C	40.10*F
Temp: 4.50*C	40.10*F
Temp: 4.50*C	40.10*F
Temp: 4.50*C	40.10*F
Temp: 4.63*C	40.33*F
Temp: 4.56*C	40.21*F
Temp: 4.56*C	40.21*F
Temp: 4.63*C	40.33*F
Temp: 4.69*C	40.44*F
Temp: 4.56*C	40.21*F
Temp: 4.63*C	40.33*F
Temp: 4.63*C	40.33*F
Temp: 4.69*C	40.44*F
Temp: 4.69*C	40.44*F
Temp: 4.69*C	40.44*F
Temp: 4.69*C	40.44*F
Temp: 4.75*C	40.55*F
Temp: 4.75*C	40.55*F
Temp: 4.75*C	40.55*F
Temp: 4.81*C	40.66*F
Temp: 4.81*C	40.66*F
Temp: 4.81*C	40.66*F
Temp: 4.81*C	40.66*F
Temp: 4.81*C	40.66*F
Temp: 4.88*C	40.78*F
Temp: 4.88*C	40.78*F
Temp: 4.88*C	40.78*F
Temp: 4.88*C	40.78*F
Temp: 4.94*C	40.89*F
Temp: 4.88*C	40.78*F
Temp: 4.88*C	40.78*F
Temp: 4.94*C	40.89*F
Temp: 4.94*C	40.89*F
Temp: 5.00*C	41.00*F
Temp: 4.94*C	40.89*F
Temp: 5.00*C	41.00*F
Temp: 5.00*C	41.00*F
Temp: 5.00*C	41.00*F
Temp: 5.06*C	41.11*F
Temp: 5.06*C	41.11*F
Temp: 5.06*C	41.11*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.19*C	41.34*F
Temp: 5.13*C	41.22*F
Temp: 5.19*C	41.34*F
Temp: 5.19*C	41.34*F
Temp: 5.25*C	41.45*F
Temp: 5.19*C	41.34*F
Temp: 5.25*C	41.45*F
Temp: 5.31*C	41.56*F
Temp: 5.31*C	41.56*F
Temp: 5.25*C	41.45*F
Temp: 5.25*C	41.45*F
Temp: 5.25*C	41.45*F
Temp: 5.38*C	41.68*F
Temp: 5.38*C	41.68*F
Temp: 5.38*C	41.68*F
Temp: 5.31*C	41.56*F
Temp: 5.38*C	41.68*F
Temp: 5.38*C	41.68*F
Temp: 5.38*C	41.68*F
Temp: 5.38*C	41.68*F
Temp: 5.44*C	41.79*F
Temp: 5.44*C	41.79*F
Temp: 5.38*C	41.68*F
Temp: 5.50*C	41.90*F
Temp: 5.50*C	41.90*F
Temp: 5.50*C	41.90*F
Temp: 5.50*C	41.90*F
Temp: 5.50*C	41.90*F
Temp: 5.50*C	41.90*F
Temp: 5.50*C	41.90*F
Temp: 5.56*C	42.01*F
Temp: 5.63*C	42.13*F
Temp: 5.63*C	42.13*F
Temp: 5.63*C	42.13*F
Temp: 5.63*C	42.13*F
Temp: 5.63*C	42.13*F
Temp: 5.63*C	42.13*F
Temp: 5.63*C	42.13*F
Temp: 5.63*C	42.13*F
Temp: 5.69*C	42.24*F
Temp: 5.69*C	42.24*F
Temp: 5.69*C	42.24*F
Temp: 5.63*C	42.13*F
Temp: 5.69*C	42.24*F
Temp: 5.69*C	42.24*F
Temp: 5.75*C	42.35*F
Temp: 5.69*C	42.24*F
Temp: 5.75*C	42.35*F
Temp: 5.75*C	42.35*F
Temp: 5.75*C	42.35*F
Temp: 5.81*C	42.46*F
Temp: 5.81*C	42.46*F
Temp: 5.81*C	42.46*F
Temp: 5.81*C	42.46*F
Temp: 5.88*C	42.58*F
Temp: 5.81*C	42.46*F
Temp: 5.88*C	42.58*F
Temp: 5.88*C	42.58*F
Temp: 5.94*C	42.69*F
Temp: 5.94*C	42.69*F
Temp: 5.88*C	42.58*F
Temp: 5.94*C	42.69*F
Temp: 5.94*C	42.69*F
Temp: 5.94*C	42.69*F
Temp: 6.00*C	42.80*F
Temp: 6.00*C	42.80*F
Temp: 6.00*C	42.80*F
Temp: 6.00*C	42.80*F
Temp: 6.00*C	42.80*F
Temp: 6.06*C	42.91*F
Temp: 6.06*C	42.91*F
Temp: 6.13*C	43.03*F             // I took it OUT of the freezer around here - temperatures should get 'warmer' now
Temp: 6.00*C	42.80*F
Temp: 5.88*C	42.58*F
Temp: 5.56*C	42.01*F
Temp: 5.38*C	41.68*F
Temp: 5.31*C	41.56*F
Temp: 5.25*C	41.45*F
Temp: 5.19*C	41.34*F
Temp: 5.19*C	41.34*F
Temp: 5.19*C	41.34*F
Temp: 5.13*C	41.22*F
Temp: 5.13*C	41.22*F
Temp: 5.06*C	41.11*F
Temp: 5.06*C	41.11*F
Temp: 5.00*C	41.00*F
Temp: 5.00*C	41.00*F
Temp: 4.88*C	40.78*F
Temp: 4.94*C	40.89*F
Temp: 4.88*C	40.78*F
Temp: 4.88*C	40.78*F
Temp: 4.81*C	40.66*F
Temp: 4.81*C	40.66*F
Temp: 4.63*C	40.33*F
Temp: 4.69*C	40.44*F
Temp: 4.44*C	39.99*F
Temp: 4.31*C	39.76*F
Temp: 4.19*C	39.54*F
Temp: 4.06*C	39.31*F
Temp: 4.13*C	39.43*F
Temp: 4.00*C	39.20*F
Temp: 3.94*C	39.09*F
Temp: 3.69*C	38.64*F
Temp: 3.56*C	38.41*F
Temp: 3.38*C	38.08*F
Temp: 3.38*C	38.08*F
Temp: 3.31*C	37.96*F
Temp: 3.19*C	37.74*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.13*C	37.63*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 3.06*C	37.51*F
Temp: 2.94*C	37.29*F
Temp: 3.00*C	37.40*F
Temp: 2.88*C	37.18*F
Temp: 2.94*C	37.29*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.75*C	36.95*F
Temp: 2.75*C	36.95*F
Temp: 2.69*C	36.84*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.56*C	36.61*F
Temp: 2.50*C	36.50*F
Temp: 2.44*C	36.39*F
Temp: 2.44*C	36.39*F
Temp: 2.38*C	36.28*F
Temp: 2.31*C	36.16*F
Temp: 2.31*C	36.16*F
Temp: 2.31*C	36.16*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.13*C	35.83*F
Temp: 2.19*C	35.94*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 1.94*C	35.49*F
Temp: 1.88*C	35.38*F
Temp: 1.94*C	35.49*F
Temp: 1.81*C	35.26*F
Temp: 1.81*C	35.26*F
Temp: 1.81*C	35.26*F
Temp: 1.75*C	35.15*F
Temp: 1.81*C	35.26*F
Temp: 1.75*C	35.15*F
Temp: 1.69*C	35.04*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.56*C	34.81*F
Temp: 1.50*C	34.70*F
Temp: 1.56*C	34.81*F
Temp: 1.44*C	34.59*F
Temp: 1.50*C	34.70*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.19*C	34.14*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.06*C	33.91*F
Temp: 1.06*C	33.91*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.81*C	33.46*F
Temp: 0.81*C	33.46*F
Temp: 0.81*C	33.46*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.56*C	33.01*F
Temp: 0.56*C	33.01*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.44*C	32.79*F
Temp: 0.50*C	32.90*F
Temp: 0.44*C	32.79*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.25*C	32.45*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.06*C	32.11*F                   // This is probably correct - POSITIVE degrees Celsius
Temp: 0.00*C	32.00*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.44*C	32.79*F
Temp: 0.44*C	32.79*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.56*C	33.01*F
Temp: 0.63*C	33.13*F
Temp: 0.56*C	33.01*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.69*C	33.24*F
Temp: 0.63*C	33.13*F
Temp: 0.69*C	33.24*F
Temp: 0.69*C	33.24*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.81*C	33.46*F
Temp: 0.75*C	33.35*F
Temp: 0.81*C	33.46*F
Temp: 0.81*C	33.46*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.94*C	33.69*F
Temp: 0.88*C	33.58*F
Temp: 0.94*C	33.69*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.06*C	33.91*F
Temp: 1.06*C	33.91*F
Temp: 1.06*C	33.91*F
Temp: 1.06*C	33.91*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.44*C	34.59*F
Temp: 1.44*C	34.59*F
Temp: 1.44*C	34.59*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.75*C	35.15*F
Temp: 1.69*C	35.04*F
Temp: 1.69*C	35.04*F
Temp: 1.75*C	35.15*F
Temp: 1.75*C	35.15*F
Temp: 1.81*C	35.26*F
Temp: 1.75*C	35.15*F
Temp: 1.88*C	35.38*F
Temp: 1.81*C	35.26*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.94*C	35.49*F
Temp: 1.88*C	35.38*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.19*C	35.94*F
Temp: 2.19*C	35.94*F
Temp: 2.25*C	36.05*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.25*C	36.05*F
Temp: 2.25*C	36.05*F
Temp: 2.25*C	36.05*F
Temp: 2.25*C	36.05*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.44*C	36.39*F
Temp: 2.44*C	36.39*F
Temp: 2.44*C	36.39*F
Temp: 2.44*C	36.39*F
Temp: 2.44*C	36.39*F
Temp: 2.56*C	36.61*F
Temp: 2.50*C	36.50*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F                //  and so on, warmer and warmer.........I pulled the plug at this point


User avatar
billf
 
Posts: 51
Joined: Mon Jun 20, 2011 9:58 am

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by billf »

In my previous post, there is a typo.

It says: but they represented properly as negative numbers

It should say: but they do not appear to represented properly as negative numbers

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by adafruit_support_mike »

You have a knack for uncovering bugs..

This time the problem seems to be in the implementation of Serial.print() for floating point values. It doesn't seem to handle negative numbers properly.

Try this for your output:

Code: Select all

Serial.print("Temp: "); 
if ( c < 0 ) { Serial.print("-"); }
Serial.print(c); 
Serial.print("*C\t"); 
if ( f < 0 ) { Serial.print("-"); }
Serial.print(f); 
Serial.println("*F");

User avatar
billf
 
Posts: 51
Joined: Mon Jun 20, 2011 9:58 am

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by billf »

I don't think that worked.

Here is the 'modified' sketch:

Code: Select all


/**************************************************************************/
/*!
This is a demo for the Adafruit MCP9808 breakout
----> http://www.adafruit.com/products/1782
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!
*/
/**************************************************************************/

#include <Wire.h>
#include "Adafruit_MCP9808.h"

// Create the MCP9808 temperature sensor object
Adafruit_MCP9808 tempsensor = Adafruit_MCP9808();

void setup() {
  Serial.begin(9600);
  Serial.println("MCP9808 demo");
  
  // Make sure the sensor is found, you can also pass in a different i2c
  // address with tempsensor.begin(0x19) for example
  if (!tempsensor.begin()) {
    Serial.println("Couldn't find MCP9808!");
    while (1);
  }
}

void loop() {
  // Read and print out the temperature, then convert to *F
  
  float c = tempsensor.readTempC();
  float f = c * 9.0 / 5.0 + 32;
  /* old code
  Serial.print("Temp: "); Serial.print(c); Serial.print("*C\t"); 
  Serial.print(f); Serial.println("*F");
  */
  
  // new code
  Serial.print("Temp: "); 
  if ( c < 0 ) { Serial.print("-"); }
  Serial.print(c); 
  Serial.print("*C\t"); 
  if ( f < 0 ) { Serial.print("-"); }
  Serial.print(f); 
  Serial.println("*F");
  delay(250);
}

Here is the data that I copied from the Serial monitor:

Code: Select all

Temp: 2.69*C	36.84*F
Temp: 2.69*C	36.84*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.50*C	36.50*F
Temp: 2.50*C	36.50*F
Temp: 2.44*C	36.39*F
Temp: 2.38*C	36.28*F
Temp: 2.44*C	36.39*F
Temp: 2.38*C	36.28*F
Temp: 2.31*C	36.16*F
Temp: 2.31*C	36.16*F
Temp: 2.25*C	36.05*F
Temp: 2.31*C	36.16*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.25*C	36.05*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.19*C	35.94*F
Temp: 2.13*C	35.83*F
Temp: 2.19*C	35.94*F
Temp: 2.13*C	35.83*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.81*C	35.26*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.81*C	35.26*F
Temp: 1.88*C	35.38*F
Temp: 1.81*C	35.26*F
Temp: 1.81*C	35.26*F
Temp: 1.75*C	35.15*F
Temp: 1.81*C	35.26*F
Temp: 1.69*C	35.04*F
Temp: 1.69*C	35.04*F
Temp: 1.69*C	35.04*F
Temp: 1.69*C	35.04*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.56*C	34.81*F
Temp: 1.50*C	34.70*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.31*C	34.36*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.19*C	34.14*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.06*C	33.91*F
Temp: 1.12*C	34.03*F
Temp: 1.06*C	33.91*F
Temp: 1.06*C	33.91*F
Temp: 1.06*C	33.91*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 0.94*C	33.69*F
Temp: 1.00*C	33.80*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.81*C	33.46*F
Temp: 0.81*C	33.46*F
Temp: 0.81*C	33.46*F
Temp: 0.75*C	33.35*F
Temp: 0.81*C	33.46*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.69*C	33.24*F
Temp: 0.69*C	33.24*F
Temp: 0.69*C	33.24*F
Temp: 0.63*C	33.13*F
Temp: 0.69*C	33.24*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.56*C	33.01*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.56*C	33.01*F
Temp: 0.56*C	33.01*F
Temp: 0.56*C	33.01*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.44*C	32.79*F
Temp: 0.44*C	32.79*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.44*C	32.79*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.06*C	32.11*F                      // probably should have gone to negative degrees Celsius some time around here
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.00*C	32.00*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.44*C	32.79*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.44*C	32.79*F
Temp: 0.44*C	32.79*F
Temp: 0.56*C	33.01*F
Temp: 0.50*C	32.90*F
Temp: 0.56*C	33.01*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.69*C	33.24*F
Temp: 0.69*C	33.24*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.69*C	33.24*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.81*C	33.46*F
Temp: 0.75*C	33.35*F
Temp: 0.81*C	33.46*F
Temp: 0.75*C	33.35*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.81*C	33.46*F
Temp: 0.88*C	33.58*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.06*C	33.91*F
Temp: 1.00*C	33.80*F
Temp: 1.00*C	33.80*F
Temp: 1.06*C	33.91*F
Temp: 1.12*C	34.03*F
Temp: 1.06*C	33.91*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.31*C	34.36*F
Temp: 1.25*C	34.25*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.50*C	34.70*F
Temp: 1.44*C	34.59*F
Temp: 1.56*C	34.81*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.56*C	34.81*F
Temp: 1.63*C	34.93*F
Temp: 1.56*C	34.81*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.69*C	35.04*F
Temp: 1.75*C	35.15*F
Temp: 1.75*C	35.15*F
Temp: 1.69*C	35.04*F
Temp: 1.81*C	35.26*F
Temp: 1.69*C	35.04*F
Temp: 1.75*C	35.15*F
Temp: 1.81*C	35.26*F
Temp: 1.81*C	35.26*F
Temp: 1.88*C	35.38*F
Temp: 1.75*C	35.15*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.88*C	35.38*F
Temp: 1.81*C	35.26*F
Temp: 1.88*C	35.38*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.13*C	35.83*F
Temp: 2.06*C	35.71*F
Temp: 2.13*C	35.83*F
Temp: 2.06*C	35.71*F
Temp: 2.19*C	35.94*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.19*C	35.94*F
Temp: 2.19*C	35.94*F
Temp: 2.19*C	35.94*F
Temp: 2.13*C	35.83*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.31*C	36.16*F
Temp: 2.25*C	36.05*F
Temp: 2.31*C	36.16*F
Temp: 2.25*C	36.05*F
Temp: 2.38*C	36.28*F
Temp: 2.31*C	36.16*F
Temp: 2.31*C	36.16*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.31*C	36.16*F
Temp: 2.44*C	36.39*F
Temp: 2.50*C	36.50*F
Temp: 2.44*C	36.39*F
Temp: 2.50*C	36.50*F
Temp: 2.44*C	36.39*F
Temp: 2.50*C	36.50*F
Temp: 2.50*C	36.50*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.69*C	36.84*F
Temp: 2.69*C	36.84*F
Temp: 2.63*C	36.72*F
Temp: 2.75*C	36.95*F
Temp: 2.69*C	36.84*F
Temp: 2.69*C	36.84*F
Temp: 2.75*C	36.95*F
Temp: 2.69*C	36.84*F
Temp: 2.75*C	36.95*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.88*C	37.18*F
Temp: 2.81*C	37.06*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 2.88*C	37.18*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.00*C	37.40*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.06*C	37.51*F
Temp: 3.19*C	37.74*F
Temp: 3.13*C	37.63*F
Temp: 3.13*C	37.63*F
Temp: 3.13*C	37.63*F
Temp: 3.13*C	37.63*F
Temp: 3.06*C	37.51*F
Temp: 3.19*C	37.74*F
Temp: 3.13*C	37.63*F
Temp: 3.19*C	37.74*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.31*C	37.96*F    // I took it out of the freezer around here
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.31*C	37.96*F
Temp: 3.31*C	37.96*F
Temp: 3.31*C	37.96*F
Temp: 3.19*C	37.74*F
Temp: 3.19*C	37.74*F
Temp: 3.13*C	37.63*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 2.94*C	37.29*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.88*C	37.18*F
Temp: 2.75*C	36.95*F
Temp: 2.69*C	36.84*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.44*C	36.39*F
Temp: 2.38*C	36.28*F
Temp: 2.31*C	36.16*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.13*C	35.83*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 1.94*C	35.49*F
Temp: 1.94*C	35.49*F
Temp: 1.88*C	35.38*F
Temp: 1.81*C	35.26*F
Temp: 1.75*C	35.15*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.56*C	34.81*F
Temp: 1.44*C	34.59*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.31*C	34.36*F
Temp: 1.25*C	34.25*F
Temp: 1.25*C	34.25*F
Temp: 1.12*C	34.03*F
Temp: 1.19*C	34.14*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 0.94*C	33.69*F
Temp: 1.00*C	33.80*F
Temp: 0.94*C	33.69*F
Temp: 0.81*C	33.46*F
Temp: 0.88*C	33.58*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.63*C	33.13*F
Temp: 0.69*C	33.24*F
Temp: 0.56*C	33.01*F
Temp: 0.56*C	33.01*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.06*C	32.11*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.00*C	32.00*F              //  This is probably where it should have gone from negative to positive degrees Celsius
Temp: 0.00*C	32.00*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.31*C	32.56*F
Temp: 0.25*C	32.45*F
Temp: 0.25*C	32.45*F
Temp: 0.37*C	32.68*F
Temp: 0.44*C	32.79*F
Temp: 0.44*C	32.79*F
Temp: 0.44*C	32.79*F
Temp: 0.44*C	32.79*F
Temp: 0.50*C	32.90*F
Temp: 0.56*C	33.01*F
Temp: 0.50*C	32.90*F
Temp: 0.56*C	33.01*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.69*C	33.24*F
Temp: 0.69*C	33.24*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.81*C	33.46*F
Temp: 0.88*C	33.58*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 1.00*C	33.80*F
Temp: 0.94*C	33.69*F
Temp: 1.06*C	33.91*F
Temp: 1.00*C	33.80*F
Temp: 1.06*C	33.91*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.12*C	34.03*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.19*C	34.14*F
Temp: 1.31*C	34.36*F
Temp: 1.25*C	34.25*F
Temp: 1.31*C	34.36*F
Temp: 1.31*C	34.36*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.37*C	34.47*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.50*C	34.70*F
Temp: 1.56*C	34.81*F
Temp: 1.50*C	34.70*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.56*C	34.81*F
Temp: 1.63*C	34.93*F
Temp: 1.56*C	34.81*F
Temp: 1.63*C	34.93*F
Temp: 1.63*C	34.93*F
Temp: 1.69*C	35.04*F
Temp: 1.69*C	35.04*F
Temp: 1.63*C	34.93*F
Temp: 1.75*C	35.15*F
Temp: 1.75*C	35.15*F
Temp: 1.75*C	35.15*F
Temp: 1.88*C	35.38*F
Temp: 1.81*C	35.26*F
Temp: 2.00*C	35.60*F
Temp: 1.94*C	35.49*F
Temp: 2.00*C	35.60*F
Temp: 2.00*C	35.60*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.06*C	35.71*F
Temp: 2.13*C	35.83*F
Temp: 2.13*C	35.83*F
Temp: 2.19*C	35.94*F
Temp: 2.19*C	35.94*F
Temp: 2.25*C	36.05*F
Temp: 2.19*C	35.94*F
Temp: 2.31*C	36.16*F
Temp: 2.25*C	36.05*F
Temp: 2.31*C	36.16*F
Temp: 2.31*C	36.16*F
Temp: 2.31*C	36.16*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.38*C	36.28*F
Temp: 2.44*C	36.39*F
Temp: 2.44*C	36.39*F
Temp: 2.50*C	36.50*F
Temp: 2.44*C	36.39*F
Temp: 2.50*C	36.50*F
Temp: 2.56*C	36.61*F
Temp: 2.56*C	36.61*F
Temp: 2.50*C	36.50*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.63*C	36.72*F
Temp: 2.56*C	36.61*F
Temp: 2.63*C	36.72*F
Temp: 2.69*C	36.84*F
Temp: 2.69*C	36.84*F
Temp: 2.69*C	36.84*F
Temp: 2.63*C	36.72*F
Temp: 2.69*C	36.84*F
Temp: 2.69*C	36.84*F
Temp: 2.75*C	36.95*F
Temp: 2.75*C	36.95*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.81*C	37.06*F
Temp: 2.88*C	37.18*F
Temp: 2.81*C	37.06*F
Temp: 2.94*C	37.29*F
Temp: 2.81*C	37.06*F
Temp: 2.94*C	37.29*F
Temp: 2.94*C	37.29*F
Temp: 3.00*C	37.40*F
Temp: 2.94*C	37.29*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 3.06*C	37.51*F
Temp: 3.00*C	37.40*F
Temp: 3.00*C	37.40*F
Temp: 3.13*C	37.63*F
Temp: 3.00*C	37.40*F
Temp: 3.13*C	37.63*F
Temp: 3.06*C	37.51*F
Temp: 3.13*C	37.63*F
Temp: 3.13*C	37.63*F
Temp: 3.19*C	37.74*F
Temp: 3.13*C	37.63*F
Temp: 3.13*C	37.63*F
Temp: 3.19*C	37.74*F
Temp: 3.19*C	37.74*F
Temp: 3.19*C	37.74*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.25*C	37.85*F
Temp: 3.31*C	37.96*F
Temp: 3.31*C	37.96*F
Temp: 3.31*C	37.96*F
Temp: 3.38*C	38.08*F
Temp: 3.44*C	38.19*F
Temp: 3.44*C	38.19*F
Temp: 3.44*C	38.19*F
Temp: 3.44*C	38.19*F
Temp: 3.44*C	38.19*F
Temp: 3.50*C	38.30*F
Temp: 3.50*C	38.30*F
Temp: 3.50*C	38.30*F
Temp: 3.56*C	38.41*F
Temp: 3.50*C	38.30*F
Temp: 3.50*C	38.30*F
Temp: 3.56*C	38.41*F
Temp: 3.56*C	38.41*F
Temp: 3.63*C	38.53*F
Temp: 3.63*C	38.53*F
Temp: 3.63*C	38.53*F
Temp: 3.63*C	38.53*F
Temp: 3.69*C	38.64*F
Temp: 3.63*C	38.53*F
Temp: 3.63*C	38.53*F
Temp: 3.69*C	38.64*F
Temp: 3.69*C	38.64*F
Temp: 3.69*C	38.64*F
Temp: 3.69*C	38.64*F
Temp: 3.75*C	38.75*F
Temp: 3.75*C	38.75*F
Temp: 3.69*C	38.64*F
Temp: 3.81*C	38.86*F
Temp: 3.75*C	38.75*F
Temp: 3.81*C	38.86*F
Temp: 3.81*C	38.86*F
Temp: 3.88*C	38.97*F
Temp: 3.81*C	38.86*F
Temp: 3.88*C	38.97*F
Temp: 3.81*C	38.86*F
Temp: 3.88*C	38.97*F
Temp: 3.94*C	39.09*F
Temp: 3.94*C	39.09*F
Temp: 3.94*C	39.09*F
Temp: 3.94*C	39.09*F
Temp: 4.00*C	39.20*F
Temp: 4.00*C	39.20*F
Temp: 4.00*C	39.20*F
Temp: 4.06*C	39.31*F
Temp: 4.06*C	39.31*F
Temp: 4.13*C	39.43*F
Temp: 4.19*C	39.54*F
Temp: 4.19*C	39.54*F
Temp: 4.19*C	39.54*F
Temp: 4.19*C	39.54*F
Temp: 4.25*C	39.65*F
Temp: 4.31*C	39.76*F      // I put my finger on the temp sensor around here
Temp: 6.06*C	42.91*F
Temp: 8.06*C	46.51*F
Temp: 9.44*C	48.99*F
Temp: 10.44*C	50.79*F
Temp: 11.19*C	52.14*F
Temp: 11.75*C	53.15*F
Temp: 12.25*C	54.05*F
Temp: 12.63*C	54.72*F
Temp: 12.88*C	55.18*F
Temp: 13.25*C	55.85*F
Temp: 13.44*C	56.19*F
Temp: 13.63*C	56.53*F
Temp: 13.81*C	56.86*F
Temp: 14.00*C	57.20*F
Temp: 14.13*C	57.43*F
Temp: 14.31*C	57.76*F
Temp: 14.44*C	57.99*F
Temp: 14.56*C	58.21*F
Temp: 14.75*C	58.55*F
Temp: 14.81*C	58.66*F
Temp: 14.94*C	58.89*F
Temp: 15.06*C	59.11*F
Temp: 15.13*C	59.22*F
Temp: 15.25*C	59.45*F
Temp: 15.31*C	59.56*F
Temp: 15.44*C	59.79*F
Temp: 15.44*C	59.79*F
Temp: 15.56*C	60.01*F
Temp: 15.63*C	60.13*F
Temp: 15.75*C	60.35*F
Temp: 15.75*C	60.35*F
Temp: 15.81*C	60.46*F
Temp: 15.94*C	60.69*F
Temp: 16.00*C	60.80*F
Temp: 16.06*C	60.91*F
Temp: 16.12*C	61.03*F
Temp: 16.19*C	61.14*F
Temp: 16.25*C	61.25*F
Temp: 16.25*C	61.25*F
Temp: 16.37*C	61.47*F
Temp: 16.37*C	61.47*F
Temp: 16.44*C	61.59*F
Temp: 16.44*C	61.59*F
Temp: 16.50*C	61.70*F
Temp: 16.50*C	61.70*F
Temp: 16.56*C	61.81*F
Temp: 16.50*C	61.70*F
Temp: 16.56*C	61.81*F
Temp: 16.62*C	61.93*F
Temp: 16.62*C	61.93*F
Temp: 16.62*C	61.93*F
Temp: 16.69*C	62.04*F
Temp: 16.69*C	62.04*F
Temp: 16.75*C	62.15*F
Temp: 16.75*C	62.15*F
Temp: 16.81*C	62.26*F
Temp: 16.81*C	62.26*F
Temp: 16.81*C	62.26*F
Temp: 16.87*C	62.38*F
Temp: 16.94*C	62.49*F
Temp: 16.94*C	62.49*F
Temp: 16.87*C	62.38*F
Temp: 16.50*C	61.70*F
Temp: 16.25*C	61.25*F
Temp: 15.94*C	60.69*F
Temp: 15.63*C	60.13*F
Temp: 15.44*C	59.79*F
Temp: 15.25*C	59.45*F
Temp: 15.00*C	59.00*F
Temp: 14.88*C	58.78*F
Temp: 14.69*C	58.44*F
Temp: 14.63*C	58.33*F
Temp: 14.44*C	57.99*F
Temp: 14.31*C	57.76*F


User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by adafruit_support_mike »

You're right.. I just brute-forced the code from the library with every possible bit combination between 0x0000 and 0x1fff and it didn't return any negative numbers.

On line 80 of the library, try replacing this:

Code: Select all

  if (t & 0x1000) temp = 256 - temp;
with this:

Code: Select all

  if (t & 0x1000) temp = temp - 256;

User avatar
billf
 
Posts: 51
Joined: Mon Jun 20, 2011 9:58 am

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by billf »

Mike, Thank you for that fix. I think that might be the answer!

I was not sure if you meant I should run with the Library (.cpp) fix AND the previous sketch (.ino) fix, so I did it both ways. The test I did with JUST the library fix was the one that worked the best. To be specific, I modified my copy of AdafruitMCP9808.cpp and then opened the Arduino interface and ran the library example sketch called
mcp9808test.ino

Here is data from the Serial monitor showing the transition from positive Celsius degrees to negative Celsius degrees:

Code: Select all

Temp: 1.00*C	33.80*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 0.94*C	33.69*F
Temp: 0.88*C	33.58*F
Temp: 0.94*C	33.69*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.88*C	33.58*F
Temp: 0.81*C	33.46*F
Temp: 0.88*C	33.58*F
Temp: 0.81*C	33.46*F
Temp: 0.81*C	33.46*F
Temp: 0.75*C	33.35*F
Temp: 0.81*C	33.46*F
Temp: 0.75*C	33.35*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.75*C	33.35*F
Temp: 0.69*C	33.24*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.63*C	33.13*F
Temp: 0.56*C	33.01*F
Temp: 0.56*C	33.01*F
Temp: 0.50*C	32.90*F
Temp: 0.56*C	33.01*F
Temp: 0.44*C	32.79*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.50*C	32.90*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.37*C	32.68*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.31*C	32.56*F
Temp: 0.25*C	32.45*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.19*C	32.34*F
Temp: 0.12*C	32.22*F
Temp: 0.12*C	32.22*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: 0.00*C	32.00*F
Temp: 0.06*C	32.11*F
Temp: 0.06*C	32.11*F
Temp: -0.06*C	31.89*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: 0.00*C	32.00*F
Temp: -0.06*C	31.89*F
Temp: -0.06*C	31.89*F
Temp: -0.06*C	31.89*F
Temp: -0.12*C	31.77*F
Temp: -0.12*C	31.77*F
Temp: -0.12*C	31.77*F
Temp: -0.12*C	31.77*F
Temp: -0.12*C	31.77*F
Temp: -0.19*C	31.66*F
Temp: -0.19*C	31.66*F
Temp: -0.19*C	31.66*F
Temp: -0.19*C	31.66*F
Temp: -0.25*C	31.55*F
Temp: -0.31*C	31.44*F
Temp: -0.25*C	31.55*F
Temp: -0.31*C	31.44*F
Temp: -0.31*C	31.44*F
Temp: -0.31*C	31.44*F
Temp: -0.31*C	31.44*F
Temp: -0.37*C	31.32*F
Temp: -0.37*C	31.32*F
Temp: -0.37*C	31.32*F
Temp: -0.37*C	31.32*F
Temp: -0.37*C	31.32*F
Temp: -0.44*C	31.21*F
Temp: -0.44*C	31.21*F
Temp: -0.44*C	31.21*F
Temp: -0.50*C	31.10*F
Temp: -0.50*C	31.10*F
Temp: -0.50*C	31.10*F
Temp: -0.63*C	30.87*F
Temp: -0.50*C	31.10*F
Temp: -0.56*C	30.99*F
Temp: -0.63*C	30.87*F
Temp: -0.63*C	30.87*F
Temp: -0.69*C	30.76*F
Temp: -0.63*C	30.87*F
Temp: -0.69*C	30.76*F
Temp: -0.69*C	30.76*F
Temp: -0.75*C	30.65*F
Temp: -0.69*C	30.76*F
Temp: -0.75*C	30.65*F
Temp: -0.75*C	30.65*F
Temp: -0.75*C	30.65*F
Temp: -0.75*C	30.65*F
Temp: -0.81*C	30.54*F
Temp: -0.81*C	30.54*F
Temp: -0.81*C	30.54*F
Temp: -0.88*C	30.42*F
Temp: -0.81*C	30.54*F
Temp: -0.81*C	30.54*F
Temp: -0.88*C	30.42*F
Temp: -0.88*C	30.42*F
Temp: -0.88*C	30.42*F
Temp: -0.94*C	30.31*F
Temp: -0.94*C	30.31*F
Temp: -0.94*C	30.31*F
Temp: -1.00*C	30.20*F
Temp: -1.06*C	30.09*F
Temp: -1.00*C	30.20*F
Temp: -1.06*C	30.09*F




Since my freezer - I mean my 'environmental test chamber' is supposed to maintain a temperature of about 0 degrees Fahrenheit, I let it run for a while, but I chose to only show part of the data here:

Code: Select all

Temp: -17.69*C	0.16*F
Temp: -17.75*C	0.05*F
Temp: -17.69*C	0.16*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.69*C	0.16*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.69*C	0.16*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.69*C	0.16*F
Temp: -17.69*C	0.16*F
Temp: -17.75*C	0.05*F
Temp: -17.69*C	0.16*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.81*C	-0.06*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.81*C	-0.06*F
Temp: -17.69*C	0.16*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.81*C	-0.06*F
Temp: -17.75*C	0.05*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.75*C	0.05*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.75*C	0.05*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.75*C	0.05*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.94*C	-0.29*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.94*C	-0.29*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F
Temp: -17.94*C	-0.29*F
Temp: -17.87*C	-0.17*F



And just to be complete, here is temperature data when I took it out of the freezer and put my thumb on the sensor to warm it up:

Code: Select all

Temp: -17.75*C	0.05*F
Temp: -17.87*C	-0.17*F
Temp: -17.81*C	-0.06*F
Temp: -17.81*C	-0.06*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.81*C	-0.06*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.75*C	0.05*F
Temp: -17.69*C	0.16*F
Temp: -17.56*C	0.39*F
Temp: -17.56*C	0.39*F
Temp: -17.44*C	0.61*F
Temp: -17.44*C	0.61*F
Temp: -17.31*C	0.84*F
Temp: -14.19*C	6.46*F
Temp: -10.00*C	14.00*F
Temp: -6.69*C	19.96*F
Temp: -4.13*C	24.57*F
Temp: -2.44*C	27.61*F
Temp: -1.06*C	30.09*F
Temp: 0.12*C	32.22*F
Temp: 0.81*C	33.46*F
Temp: 1.56*C	34.81*F
Temp: 2.19*C	35.94*F
Temp: 2.75*C	36.95*F
Temp: 3.13*C	37.63*F
Temp: 3.63*C	38.53*F
Temp: 3.94*C	39.09*F
Temp: 4.19*C	39.54*F
Temp: 4.56*C	40.21*F
Temp: 4.81*C	40.66*F
Temp: 4.94*C	40.89*F
Temp: 5.13*C	41.22*F
Temp: 5.44*C	41.79*F
Temp: 5.81*C	42.46*F
Temp: 6.06*C	42.91*F
Temp: 6.31*C	43.36*F
Temp: 6.38*C	43.47*F
Temp: 6.63*C	43.93*F
Temp: 6.75*C	44.15*F
Temp: 6.94*C	44.49*F
Temp: 7.13*C	44.83*F
Temp: 7.31*C	45.16*F
Temp: 7.50*C	45.50*F
Temp: 7.69*C	45.84*F
Temp: 7.88*C	46.18*F
Temp: 8.00*C	46.40*F
Temp: 8.13*C	46.63*F
Temp: 8.31*C	46.96*F
Temp: 8.50*C	47.30*F
Temp: 8.63*C	47.53*F
Temp: 8.75*C	47.75*F
Temp: 8.88*C	47.97*F
Temp: 9.06*C	48.31*F
Temp: 9.19*C	48.54*F
Temp: 9.31*C	48.76*F
Temp: 9.44*C	48.99*F
Temp: 9.50*C	49.10*F
Temp: 9.63*C	49.33*F
Temp: 9.75*C	49.55*F
Temp: 9.94*C	49.89*F
Temp: 9.94*C	49.89*F
Temp: 10.06*C	50.11*F
Temp: 10.13*C	50.22*F


Please let me know when the library is officially updated.

Thank you once again for your help with this problem.

Bill

User avatar
adafruit2
 
Posts: 22148
Joined: Fri Mar 11, 2005 7:36 pm

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by adafruit2 »

Ironically, this sensor came out at the exact wrong time - it's too nice out to test with sub-zero temps! :) ok please try the current library. it now has:

Code: Select all

float Adafruit_MCP9808::readTempC( void )
{
  uint16_t t = read16(MCP9808_REG_AMBIENT_TEMP);

  float temp = t & 0x0FFF;
  temp /=  16.0;
  if (t & 0x1000) temp -= 256;

  return temp;
}

User avatar
billf
 
Posts: 51
Joined: Mon Jun 20, 2011 9:58 am

Re: Strange data from MCP9808 High Accuracy I2C Temperature

Post by billf »

I erased all files that had on my computer related to the Adafruit_MCP9808 library and downloaded new files. I opened the Aduino IDE and ran the library example file called mcp9808test.ino

Everything looks like it is working correctly now. I took the temperature sensor down to just below 0 degrees Fahrenheit and then I took it up to just above 180 degrees Fahrenheit and it worked well. I checked the transitions from positive degrees to negative degrees and from negative degrees to positive degrees for both Celsius and Fahrenheit and it all looks good.

Thank you for your guidance and support with the Adafruit products. It certainly makes things a lot easier for me (and others).

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