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Equipment Discussions >> ATM, Optics and DIY Forum

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Carpal Tunnel

Reged: 02/18/11

Loc: Rancho Cucamonga, CA
Re: Instrumenting a Dob with Temperature Probes new [Re: tjmck]
      #5946827 - 06/29/13 04:03 PM


Look at Adafruit Industries. They have all the solutions you are looking for. If you want to go with K type thermocouples - $10 per, DS18B20 - $4 per, TMP36 - $2 per. Most popular controllers including Arduino and Rasperry Pi, Thermocouple Amplifier MAX31855 breakout board. They also have a data logger sheild for Arduino that incorporates a real time clock and SD card for data storage. Most importantly, they have tutorials on how to setup all of the items and a support community to solve issues.

As for measurement precision, a Class 1 K-Type thermocouple is only rated 1.5C Accuracy from -40C to +375C. For the DS18B20 0.5C Accuracy from -10C to +85C.

There a lots of ways to do what you want. I recently assembled a lab freezer temperature mapping system using an Arduino, Data Logger Shield and 16x DS18B20s that was programmed to take measurements off all 16 sensors every 6 seconds. The data was stored as a CSV file and easily read into a spreadsheet. You could also add a LCD and keyboard or touch screen and even run the whole thing from batteries if you wanted.



The accuracy figure quoted for the Class 1 Type K might be the absolute accuracy over the entire range, I am only interested in relative precision in 5C to 35C (41F to 95F) roughly (OC to 40C absolute limit - 32F to 104F).

Thanks, Omega had K-type thermocouples for only $3.60 per (pack of 5) and the voltage output datasheet in the range of interest suggested precision of 0.05C or better - but of course that is only one component in overall system precision.

Precision of 0.5 C or better between sensors (not overall accuracy, which could be less) would be what I am looking for. What is critical is the precision of the differential between sensors at a particular time. Neither absolute accuracy nor stability of individual sensor reading over long periods is important, they just all have to agree closely at the same time.

It sounds like I should get into Arduino at some point, just because. Not sure how soon I want to tackle it though.

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