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drhaney / pt100rtd

Pt100 sensor resistance-to-temperature conversion, ITS-90 conformant
BSD 2-Clause "Simplified" License
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Increase RTD reading #1

Closed Fabien-Roots closed 6 years ago

Fabien-Roots commented 6 years ago

Hi, I wont to know if it possible to increase the RTD Reading to the MAX31865.cpp, to have better resolution.

Actually the code give : rtd: 0x2015, ohms: 107.77

For my, instrumentation i needed rtd: 0x2015, ohms: 107.77# 7

Sorry i'm not a expert with the MAX31865, and i need help.

Thanks in advance

drhaney commented 6 years ago

The MAX31865 is a 15-bit device that confers 0.013 ohms resolution using a 430 ohm reference resistor. That's all you get. It doesn't make sense to create a resolution beyond that of the measuring chip.

However, you can print at any decimal resolution you like. See line 109 in pt100rtd/examples/pt100_temperature/ where it says

Serial.print(", ohms: ") ; Serial.println(ohms,2) ;

Change the 2 to any number between 1 and 15, the maximum decimal point resolution of 'double' type real numbers in C++. The full 15 decimal points is contained the the variable ohms.

Fabien-Roots commented 6 years ago

Thanks for the answer, i already make this (ohms,3) but the value have a résolution of 0,02°C, i cant have a better resolution, to have précise variation ( for example : 12.0312, 12.0311, 12.0313) i have only 12.030, 12.050, 12.010 ... Did you think that is possible to increase the RTD read for the MAX31865, because this value it's enought accurate to have a résolution of 0.001°C. Best regards