Max6675 pin 2 confusion

metron9

From the datasheet.


Alumel Lead of Type-K Thermocouple.
Should be connected to ground
externally.


I have read through some of the trials and tribulations of others on using the max6675. My plan is to make a small board with a regulator and a 6675 where the thermocouple leads are soldered to that board and then have a 5 pin connector (+DC,-DC,SPI) strip to connect that to my main controller board.

I am just not sure what the datasheet means by Externally. T+ and T- are connected to the thermocouple leads but what is connected externally?

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

Franklin

I think it means T- should be tied to ground.

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- Stephen

PJAllen

http://ryanjmclaughlin.com/2009/07/max6675-thermocouple-interface/

Tracy Allen

The differential thermocouple input is high impedance and needs a path for amplifier bias currents to flow to ground. Without that, it can drift outside the common mode range and is extra sensitive to AC and noise pickup. Those effects can ruin the accuracy. Here is another reference for the Stamp... emesystems.com/OL2therm.htm.

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Tracy Allen
www.emesystems.com