Cost of PT100 sensor calibration - Page 1
Forum section: electronics / general

author: benseno
author_rank: Regular Contributor
timestamp: March 04, 2025, 07:59:55 pm
content: I am working on project (DIY) which includes temperature measurements too.While the job doesn't require too precise measurement, i got curious about cost requiring to calibrate cheap class B PT100 at home for a temperature range -40 +70 Celsius and maximum achievable precision.Of course, budget is the main limitation here - 2-3K$.The list of equipment could be:- diy water bath- 6.5 digits multimeter capable of measuring sensors (around 1K$)- TP water as a first reference- boiling water as a second, or accurate body thermometer along with water bath as a second reference point in calibration.Signal conditioning circuit cost is not taken into the consideration.Is +-0.15 C precision can be achieved using above setup?Thanks

author: mendip_discovery
author_rank: Super Contributor
timestamp: March 04, 2025, 09:03:53 pm
content: Use this to get the low end,https://www.nist.gov/system/files/documents/2017/04/28/Ice-Melting-Point-Validation-Method-for-Data-Loggers.pdfPersonally, I would get a good quality probe calibrated and use that as a comparison even in an ice bath or hotblock.

author: bdunham7
author_rank: Super Contributor
timestamp: March 04, 2025, 09:38:36 pm
content: If you're spending that kind of money then get a Class A 4-wire RTD.I don't think you need to go with vacuum apparatus for an actual triple-point setup, atmospheric pressure ice-baths are pretty accurate and you can compensate for atmospheric pressure, although the coefficient is pretty low and probably can be ignored in most cases at that accuracy level.The boiling point is probably harder to do accurately and you need at least an accurate barometric reading for compensation--that coefficient is not so low!All in all, it sounds like a great excuse to buy a 6.5-digit DMM. Keithley DMM6500 would be a good choice. I think you probably can acheive your calibration goal and hopefully if you start with good equipment such as I suggest your corrections will be very small.

author: pdenisowski
author_rank: Super Contributor
timestamp: March 05, 2025, 05:24:55 am
content: Quote from: bdunham7 on March 04, 2025, 09:38:36 pmExactly. Absolutely want to use 4 wire in this case.

author: HighVoltage
author_rank: Super Contributor
timestamp: March 05, 2025, 10:26:06 am
content: For that kind of money you can even get an original FLUKE RTD temparature sensor with calibration certificateI showed myFluke 5616-12 RTDProbe here:https://www.eevblog.com/forum/metrology/high-resolution-temperature-measurement-with-no-accuracy-requirement/msg4621303/#msg4621303It came with a extensive calibration sheet, showing many temperature points.

author: Overspeed
author_rank: Frequent Contributor
timestamp: March 05, 2025, 04:13:11 pm
content: Quote from: benseno on March 04, 2025, 07:59:55 pmHelloTake in consideration than : calibration is not only two point that a minimum of 3 to display linearity as linearity is also an important factora triple point water is not exactly a ice bath but you can built something close if your target is only +/- 0.15 deg Chow to use a triple point water from Flukehttps://youtu.be/EkFmrWsSzgAfor 100 deg C , you need to take care of the atmospheric pressuremain concern is points between 0 and 100 as gallium point is quite ( rather costly ) so easiest way is to use dry blockhttps://youtu.be/U9-kKBZJHmARegardsOS

author: Doctorandus_P
author_rank: Super Contributor
timestamp: March 06, 2025, 08:34:13 pm
content: What do you mean with "maximum achievable precision". My first guess, is that when you use "cheap" sensors, that long term drift of the sensor itself is going to be the main limitation. What is the use of calibrating to 0.01K if your sensor deviates 0.5K half a year later?To get an idea of what short of precision is achievable for sensors in your budget range, select a bunch of them and then get and study their datasheets.

author: Overspeed
author_rank: Frequent Contributor
timestamp: March 07, 2025, 07:53:53 am
content: Quote from: Doctorandus_P on March 06, 2025, 08:34:13 pmHelloI agree that need clarification , that possible to use lower Pt100 quality for single value or limited range measurement as 23 deg C in a lab , no need to have a perfect linearity up to 100 deg or more .If the goal is to measurement temp from 0 to 70 deg C in the 0.15 deg C that another challenge with low cost Pt100 except to purchase several batches and sort them which is time consumingRegardsOS

author: Henrik_V
author_rank: Regular Contributor
timestamp: March 10, 2025, 05:36:59 pm
content: Ice bath and a clinical thermometer (in a stirred water bath) should give you u about 50mK at 0°C and 37°C.And always remember: The thermometer will report the temperature ist feels, that may or may not be the temperature you want to measure