Thermocouple Amplifier MAX31855

by **ribo** » Mon Jun 11, 2012 11:44 pm

Are you checking the board in NY with an ice bath and getting the right readings?

I un-commented all the Serial.prints (even the block commented one).
Here is the output after compiling and running:

MAX31855 test
Internal Temp = 1681A50
Internal Temp: 26.31
26.31
C = 16C1A50
0x16C1A50
Internal Temp: 26.31
5B
22.75
F = 16C1A50
0x16C1A50
Internal Temp: 26.31

by **adafruit** » Tue Jun 12, 2012 9:39 am

we're confused, that looks pretty reasonable - the internal temp is 26C and the measured temp is ~23C

by **ribo** » Thu Jun 14, 2012 12:13 am

yes this a reasonable error for measuring room temperature.
However -3600 deg F for an ice bath?
Did you try to test an ice bath yet?

by **adafruit** » Thu Jun 14, 2012 8:57 am

We'll try that today - can you post up the full output with hex debugging for an ice bath? We'll compare!

by **adafruit** » Thu Jun 14, 2012 12:10 pm

OK we tried another ice bath and got down to about 4 *C - can you show a log of it cooling down, at what point do you see the big problem?

by **ribo** » Thu Jun 14, 2012 11:50 pm

Here is a cool down from room temp to ice bath and then back to room temp.

Code: Select all: I .12 24.12 C = 1641820 0x1641820 Internal Temp: 24.12 59 22.25 F = 1681830 0x1681830 Internal Temp: 24.19 5A 72.50 MAX31855 test Internal Temp = 1641810 Internal Temp: 24.06 24.06 C = 1601810 0x1601810 Internal Temp: 24.06 58 22.00 F = 1601810 0x1601810 Internal Temp: 24.06 58 71.60 Internal Temp = 1601820 Internal Temp: 24.12 24.12 C = 1641820 0x1641820 Internal Temp: 24.12 59 22.25 F = 1641820 0x1641820 Internal Temp: 24.12 59 72.05 Internal Temp = 1601820 Internal Temp: 24.12 24.12 C = 1641820 0x1641820 Internal Temp: 24.12 59 22.25 F = 1601820 0x1601820 Internal Temp: 24.12 58 71.60 Internal Temp = 1601830 Internal Temp: 24.19 24.19 C = 1601830 0x1601830 Internal Temp: 24.19 58 22.00 F = 1641830 0x1641830 Internal Temp: 24.19 59 72.05 Internal Temp = 1601830 Internal Temp: 24.19 24.19 C = 1601830 0x1601830 Internal Temp: 24.19 58 22.00 F = 1601830 0x1601830 Internal Temp: 24.19 58 71.60 Internal Temp = 1641830 Internal Temp: 24.19 24.19 C = 1641820 0x1641820 Internal Temp: 24.12 59 22.25 F = 1601820 0x1601820 Internal Temp: 24.12 58 71.60 Internal Temp = 1401830 Internal Temp: 24.19 24.19 C = 13C1830 0x13C1830 Internal Temp: 24.19 4F 19.75 F = 1301830 0x1301830 Internal Temp: 24.19 4C 66.20 Internal Temp = FFAC1830 Internal Temp: 24.19 24.19 C = FFA41830 0xFFA41830 Internal Temp: 24.19 3FE9 -2042.25 F = FFA41830 0xFFA41830 Internal Temp: 24.19 3FE9 -3644.05 Internal Temp = FFA81830 Internal Temp: 24.19 24.19 C = FFA81830 0xFFA81830 Internal Temp: 24.19 3FEA -2042.50 F = FFA81830 0xFFA81830 Internal Temp: 24.19 3FEA -3644.50 Internal Temp = FFB81830 Internal Temp: 24.19 24.19 C = FFB81830 0xFFB81830 Internal Temp: 24.19 3FEE -2043.50 F = FFB81830 0xFFB81830 Internal Temp: 24.19 3FEE -3646.30 Internal Temp = FFA81830 Internal Temp: 24.19 24.19 C = FFAC1830 0xFFAC1830 Internal Temp: 24.19 3FEB -2042.75 F = FFA81830 0xFFA81830 Internal Temp: 24.19 3FEA -3644.50 Internal Temp = FFA01830 Internal Temp: 24.19 24.19 C = FFA41830 0xFFA41830 Internal Temp: 24.19 3FE9 -2042.25 F = FFA41830 0xFFA41830 Internal Temp: 24.19 3FE9 -3644.05 Internal Temp = FFA01830 Internal Temp: 24.19 24.19 C = FFA41830 0xFFA41830 Internal Temp: 24.19 3FE9 -2042.25 F = FFA01830 0xFFA01830 Internal Temp: 24.19 3FE8 -3643.60 Internal Temp = FF9C1840 Internal Temp: 24.25 24.25 C = FFA01830 0xFFA01830 Internal Temp: 24.19 3FE8 -2042.00 F = FFA01840 0xFFA01840 Internal Temp: 24.25 3FE8 -3643.60 Internal Temp = FF9C1830 Internal Temp: 24.19 24.19 C = FFA01830 0xFFA01830 Internal Temp: 24.19 3FE8 -2042.00 F = FF9C1830 0xFF9C1830 Internal Temp: 24.19 3FE7 -3643.15 Internal Temp = FF9C1830 Internal Temp: 24.19 24.19 C = FFA01840 0xFFA01840 Internal Temp: 24.25 3FE8 -2042.00 F = FF9C1830 0xFF9C1830 Internal Temp: 24.19 3FE7 -3643.15 Internal Temp = FF981840 Internal Temp: 24.25 24.25 C = FF9C1830 0xFF9C1830 Internal Temp: 24.19 3FE7 -2041.75 F = FF9C1830 0xFF9C1830 Internal Temp: 24.19 3FE7 -3643.15 Internal Temp = FF981830 Internal Temp: 24.19 24.19 C = FF981830 0xFF981830 Internal Temp: 24.19 3FE6 -2041.50 F = FF9C1840 0xFF9C1840 Internal Temp: 24.25 3FE7 -3643.15 Internal Temp = FF9C1830 Internal Temp: 24.19 24.19 C = FFA01830 0xFFA01830 Internal Temp: 24.19 3FE8 -2042.00 F = FFA01830 0xFFA01830 Internal Temp: 24.19 3FE8 -3643.60 Internal Temp = FF9C1840 Internal Temp: 24.25 24.25 C = FF9C1830 0xFF9C1830 Internal Temp: 24.19 3FE7 -2041.75 F = FF9C1840 0xFF9C1840 Internal Temp: 24.25 3FE7 -3643.15 Internal Temp = FF981840 Internal Temp: 24.25 24.25 C = FF981840 0xFF981840 Internal Temp: 24.25 3FE6 -2041.50 F = FF981840 0xFF981840 Internal Temp: 24.25 3FE6 -3642.70 Internal Temp = FF501840 Internal Temp: 24.25 24.25 C = FF481840 0xFF481840 Internal Temp: 24.25 3FD2 -2036.50 F = FF441840 0xFF441840 Internal Temp: 24.25 3FD1 -3633.25 Internal Temp = FF381840 Internal Temp: 24.25 24.25 C = FF381840 0xFF381840 Internal Temp: 24.25 3FCE -2035.50 F = FF481840 0xFF481840 Internal Temp: 24.25 3FD2 -3633.70 Internal Temp = 2C1840 Internal Temp: 24.25 24.25 C = 341840 0x341840 Internal Temp: 24.25 D 3.25 F = 3C1840 0x3C1840 Internal Temp: 24.25 F 38.75 Internal Temp = FF981840 Internal Temp: 24.25 24.25 C = FF941840 0xFF941840 Internal Temp: 24.25 3FE5 -2041.25 F = FF9C1840 0xFF9C1840 Internal Temp: 24.25 3FE7 -3643.15 Internal Temp = 1101840 Internal Temp: 24.25 24.25 C = 12C1850 0x12C1850 Internal Temp: 24.31 4B 18.75 F = 1381840 0x1381840 Internal Temp: 24.25 4E 67.10 Internal Temp = BC1840 Internal Temp: 24.25 24.25 C = C01840 0xC01840 Internal Temp: 24.25 30 12.00 F = D01840 0xD01840 Internal Temp: 24.25 34 55.40 Internal Temp = E01840 Internal Temp: 24.25 24.25 C = 1581850 0x1581850 Internal Temp: 24.31 56 21.50 F = 1641840 0x1641840 Internal Temp: 24.25 59 72.05 Internal Temp = 1381850 Internal Temp: 24.31 24.31 C = 1401850 0x1401850 Internal Temp: 24.31 50 20.00 F = 1381840 0x1381840 Internal Temp: 24.25 4E 67.10 Internal Temp = 1501850 Internal Temp: 24.31 24.31 C = 1541840 0x1541840 Internal Temp: 24.25 55 21.25 F = 1541840 0x1541840 Internal Temp: 24.25 55 70.25 Internal Temp = 1641850 Internal Temp: 24.31 24.31 C = 1681850 0x1681850 Internal Temp: 24.31 5A 22.50 F = 16C1850 0x16C1850 Internal Temp: 24.31 5B 72.95 Internal Temp = 1C81850 Internal Temp: 24.31 24.31 C = 1CC1850 0x1CC1850 Internal Temp: 24.31 73 28.75 F = 1CC1850 0x1CC1850 Internal Temp: 24.31 73 83.75 Internal Temp = 1BC1850 Internal Temp: 24.31 24.31 C = 1BC1840 0x1BC1840 Internal Temp: 24.25 6F 27.75 F = 1BC1850 0x1BC1850 Internal Temp: 24.31 6F 81.95 Internal Temp = 1B01850 Internal Temp: 24.31 24.31 C = 1B01850 0x1B01850 Internal Temp: 24.31 6C 27.00 F = 1B01850 0x1B01850 Internal Temp: 24.31 6C 80.60 Int

by **adafruit** » Fri Jun 15, 2012 11:46 am

OK thanks, that was the information we needed to fix the problem

download the library, completely delete the old version and try now

thanks!

by **ribo** » Sat Jun 16, 2012 12:05 pm

Thanks -- working much better with the latest library.

by **petespaco** » Tue Jun 19, 2012 9:09 am

Aren't you folks a little nervous about using the crimped spade lugs that are on the end of those thermocouples? Aren't you creating another separate cold junction? And, aren't you introducing another source for noise, etc.?

by **amconcepts** » Tue Jul 03, 2012 2:23 pm

Hey so I just got my MAX31855 and downloaded the "new" libraries but I'm getting very similar results to those of ribo. Has the libraries changed in the last ~20 days?

-AM

by **adafruit_support_bill** » Tue Jul 03, 2012 3:24 pm

The last update was 18 days ago.https://github.com/adafruit/Adafruit-MAX31855-library

by **Mike H** » Thu Jul 12, 2012 12:28 am

I am also having trouble with negative readings. Seem to hover around -200 C to -300 C at room temp and it jumps around a lot. I can get it up to about -50 C if I pinch it between my fingers. Trying to determine if it is a bad board, thermocouple, or code. Internal temp appears to read fine. Anyone else still having trouble with this?

by **adafruit_support_bill** » Thu Jul 12, 2012 5:10 am

Make sure you have the latest libraries, and add a 0.1uF cap at the terminal block in parallel with the thermocouple.

Thermocouple Amplifier MAX31855

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