MAX31855 Thermocouple Amplifier and Multiplexer
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MAX31855 Thermocouple Amplifier and Multiplexer

by Meissnerb44 on Tue Jan 08, 2013 6:35 pm

I am trying to hook up the Max31855 breakout board to a Sparkfun multiplexer breakout board which holds the 16-Channel Analog/Digital Multiplexer/Demultiplexer CD74HC4067. I want to hook up 5 thermocouples to the multiplexer so that they can all be read without having to use 5 separate thermocouple amplifiers. I am having a hard time figuring out how this would work because I believe that the Max31855 breakout would need to receive the signal from both thermocouple wires at the same time. I could very well be mistaken but I am confused on how or if it could work. Any suggestions??

Thanks,
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Re: MAX31855 Thermocouple Amplifier and Multiplexer

by adafruit_support_rick on Tue Jan 08, 2013 7:14 pm

Well, you could use two multiplexers - one for each side of the thermocouples.

Or you could use 5 MAX31855 breakouts. You would need 1 CLK output, 1 data input, and 5 chip select outputs on your microcontroller.

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Re: MAX31855 Thermocouple Amplifier and Multiplexer

by cmccoy21 on Tue Jun 10, 2014 9:28 am

Hi,

I'm fairly new to electronics, can you help me better understand how one would connect the 8:1 multiplexers to the MAX31855 and Arduino UNO?

From my understanding, one multiplexer would take in the positive leads of the thermocouples and another multiplexer would take in the negative leads into the 8 analog inputs. Then the multiplexers each would send one analog output (one positive and one negative) to the terminal of the thermocouple amplifier.

But what about the select pins? Do those connect to the arduino? If there are 3 select pins per multiplexer, would the arduino need 6 analog pins?

Thanks!
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Re: MAX31855 Thermocouple Amplifier and Multiplexer

by adafruit_support_rick on Tue Jun 10, 2014 10:16 am

You can probably run the select pins in parallel. However, we don't support the multiplexer here - that's a SparkFun product. I'm not familiar with them, so I can't give you a definitive answer.

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