MAX31855 Thermocouple Amplifier Breakout Board Giving Bad Re

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jessesmith
 
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MAX31855 Thermocouple Amplifier Breakout Board Giving Bad Re

Post by jessesmith »

On June 10 I ordered 3 MAX31855 breakout boards. I was thrilled to get them so quickly, and got them all communicating with my Arduino in no time flat thanks to your tutorials. Initially though I only had one thermocouple to test the three out with. Everything looked OK near room temperature (maybe reading a little too low, like 34.5 celsius instead of 36, but I figured it was within their quoted accuracy and I could correct any linear offset in software later).

Unfortunately, once I got my order of thermocouples from OMEGA I tested out all three MAX31855 simultaneously. They don't really agree with each other very well, so I tested out the MAX31855 boards with hot and cold baths and used another thermometer for reference. I used a "FLUKE 51 II THERMOMETER" and an expensive temperature controller with platinum 1 kiloohm resistance temperature detector (with an absurdly precise millikelvin readout). These two references have nearly identical accuracy as far as I can tell -- but both differ from the MAX31855 readings by significant amounts (nearly 10 degrees celsius when measuring a 70 degree celsius bath). I double checked, and the MAX31855 chip on the board is for the K-type thermocouples which I have.

From searching the Adafruit support forum, and reading a thread on the eevblog forum, it appears the MAX31855 chips on my breakout boards might come from a bad batch Maxim released. Is there any way to get these replaced? I'm more than happy to ship these back to you.

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Franklin97355
 
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Re: MAX31855 Thermocouple Amplifier Breakout Board Giving Ba

Post by Franklin97355 »

There was a bad batch of the amplifiers. could you post a clear picture of the chip or copy off the code from the chip and post that?

The label of the chip on the breakout board:

M31855k
1345A2
253AK (also 253AJ I think)

jessesmith
 
Posts: 3
Joined: Tue Jul 01, 2014 2:46 pm

Re: MAX31855 Thermocouple Amplifier Breakout Board Giving Ba

Post by jessesmith »

After trying to photograph it a dozen times, this is the best I got
Image

All three MAX31855 chips say
"M31855K
1345A2
253AK"

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Franklin97355
 
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Re: MAX31855 Thermocouple Amplifier Breakout Board Giving Ba

Post by Franklin97355 »

Thanks. Please email [email protected] with a link to this thread for a refund at this time we don't have any confirmed good stock. If you want to get a notification when they come in visit this page https://www.adafruit.com/product/269

jessesmith
 
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Joined: Tue Jul 01, 2014 2:46 pm

Re: MAX31855 Thermocouple Amplifier Breakout Board Giving Ba

Post by jessesmith »

Thank you franklin97355. I'm a bit bummed out, but I realize it's not adafruit's fault. Thanks for your help.

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