MAX31855 with washer thermocouple problem
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MAX31855 with washer thermocouple problem

by RosscoS on Tue Nov 13, 2012 8:00 pm

I have a MAX31855 breakout board that I am using with a washer type thermocouple so that I can attach it to a boiler.

When the thermocouple is sitting in air, it reads fine, however when I attach it to the boiler, the serial display indicates a problem with the thermocouple.

I have connected the GND of the boiler to the Arduino & MAX31855 GND.
I have tried putting Mica washers between the washer and the boiler, also between the washer and the screw with zero success.

Thanks in advance for any assistance.
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Re: MAX31855 with washer thermocouple problem

by adafruit_support_bill on Wed Nov 14, 2012 10:01 am

The MAX31855 is not compatible with grounded junction thermocouples. You need to insulate the washer from the grounded tank.
I have tried putting Mica washers between the washer and the boiler, also between the washer and the screw with zero success.

Mica washers won't prevent the screw from contacting the sides of the hole in the washer.
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Re: MAX31855 with washer thermocouple problem

by Nidaybak on Wed Nov 14, 2012 12:01 pm

It is remarkable, very much the helpful information
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Re: MAX31855 with washer thermocouple problem

by RosscoS on Fri Nov 16, 2012 4:09 am

adafruit_support wrote:The MAX31855 is not compatible with grounded junction thermocouples. You need to insulate the washer from the grounded tank.


Would I be correct in saying that one alternative would be a ungrounded junction washer type thermocouple? Or am I way off?
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Re: MAX31855 with washer thermocouple problem

by adafruit_support_bill on Fri Nov 16, 2012 6:03 am

ungrounded junction washer type thermocouple?

Yes, that should work.
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Re: MAX31855 with washer thermocouple problem

by RosscoS on Fri Nov 16, 2012 4:15 pm

A bunch of teflon tape on the screw and a few mica washers did the trick!
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