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Several thermocouples to one MAX31856?

asrock70

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I need to accurately measure a few (8) thermocouples , Using 8 pcs MAX31856 is economically and size unsuitable , my idea is use 1 x 19bit Thermocouple to Digital Converter MAX31856 + 1x analog swith ADG1607.

Can anyone estimate the impact of using an analog switch on accuracy?
 

KlausST

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Hi,

Did you do a forum search? If I remember right, then there was a similar discussion..

Klaus
 

asrock70

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Do you mean this thread, for example?
I didn't learn anything interesting from that .
In this reference design is mux used for switching Thermocouple
Her is solution for 16 Thermocouple , but nowhere does it address the impact on accuracy .

Due to the small MAX input currents, the resistance of the switch is not a problem, but I don't know what effect they will have leakage current of Mux.
 

FvM

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I think your question is essentially answered in the linked thread, there's also an estimation of expectable voltage error., presume you can convert it into temperature error.

I alsoexpect that you can calculate error terms based on TC and mux resistance yourself.
 

danadakk

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This is an example of a single chip solution using PSOC. Shown is two channels, a thermocoule and
a thermistor. To add channels simply config mux for more channels. I think you could do > 16 channels.
You could also mix Thermocouple types. All on one chip. Ignore the reference to the thermocouple kit,
shown below in IDE, you really do not need that.

1593948916226.png

Note most chip resources unused, see right hand window for resources used/left.
The unused of course you can use for other tasks. Core has ARM M3 in it.

https://www.cypress.com/file/123806/download ap note


Compiler and IDE free, https://www.cypress.com/products/psoc-creator-integrated-design-environment-ide

Boards to consider for dev -



Catalog of components onchip, attached. Note in PSOC land a component is an
onchip resource. Note each component has a lib of API calls to manipulate component
in code. Rare you have to write a driver for anything.

Tons of videos for learning. Basically drag and drop, wire on and off chip using wire tool,
and using APIs implement code.


Regards, Dana.
 

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