Questions on pt100 probes

[Sensorcat]

Sensorcat
You know, you made a trivial mistake then. The ice is supposed to be moist/moistened and not swim in "cold water". Water has the highest density at 4 degrees Celsius. This causes ice to "dribble to the bottom of the vessel", while ice has a lower density at approximately 0 degrees Celsius, so it "floats". This is one of the reasons why fish survive in lakes in winter. The ice in the thermos must be constantly "drained" of excess water - this is NECESSARY in such an implementation. The sensor is not meant to be "pushed to the very bottom of the vessel". The sensor is to be in the "middle part of the snow block" - pressed.
There is a very nice pdf explaining how to do this on the New Zeland National Laboratory website.

Although you should not think that my own experiments involved a single icecube floating on water, I do know now, thanks to the valuable resources posted by mzzj, that the ice bath has to meet harder requirements with little tolerance (for instance, having small pieces of ice). That's why I prefer to see this as difficult, not as easy, which was the first point I wanted to make in this thread. Murphy is my witness that it is preferable to see tasks as difficult rather than easy, if you want to achieve stable and reliable results. Note that I never claimed that I know how to prepare a good ice bath, so I did not make 'a trivial mistake.'

And this leads to my second point: If you need reliablity, you need a process. A process makes all relevant factors explicit, not implicit, and avoids the human factor. Standards that have to do with assurance of quality or safety therefore involve auditing, with the auditor always asking one question, in endless variations: 'How do you make sure that ...?' And if you reply 'I know that.' - 'It's easy.' - 'Never has been a problem.' you should not get your certificate (provided that the auditor does his job properly), because that's not a process. And having a process is certainly not limited to technology with the highest requirements! Whenever not meeting requirements (tight or loose) has dire consequences, you need a process. Who does not understand this should not think of designing something serious, because if you do anyway, things like this happen:
https://www.eevblog.com/forum/chat/baltimore-francis-scott-key-bridge-collapse/

[MiDi]

Sensorcat
There is a very nice pdf explaining how to do this on the New Zeland National Laboratory website.

Standards Lab NZ Document

[Yuu]

Does anyone have a title for whatever this Nicholas & White 2001 paper/text is?

I'm interested how they derive their "polishing function." It doesn't appear to be some newton root finding method.

Edit: found it
Nicholas J V and White D R (2001) Traceable Temperatures: An Introduction to
Temperature Measurement and Calibration (John Wiley and Sons, Chichester).

[mendip_discovery]

Traceable Temperatures, produced by Wiley.

Physical copies are hard to come by.

[arvee]

Hi,

Fluke has a webpage for the PT100 https://us.flukecal.com/pt100-calculator

Here is my calculator in HTML.

Details of the Newton root iteration be found in the comments of the calculator.

RV

[BarrowBoy]

Here I go again. Newbie, 10th post. Very addictive forum. Love Temperature discipline, but again not typical hands on, although I know and am trained in creating a TPW, and I don't mean making one from scatch...lol. I mean the process of creating the all important ice mantle within the TP cell. Try making one....your first skill is to learn  glassblowing, and bonding dissimilar glasses.

If range is 0-100C, then any reason a Thermistor is not being used? They have a far greater value change across their working range and are very good in this temperature range IMO. Below is something I found online which is a good summary of why I ask.

[BarrowBoy]

NIST, BIPM and NZ national standards labs have some good guides:
https://www.measurement.govt.nz/resources/#collapse-control-1-5
https://nvlpubs.nist.gov/nistpubs/Legacy/TN/nbstechnicalnote1411.pdf
https://www.bipm.org/documents/20126/41773843/Specialized-FPs-above-0C.pdf/10265617-c79f-0ea5-8da9-8d359e21c6be



If I needed to verify the ice bath I have 3 resistance bridges, 5 triple point cells and close to dozen SPRT's at my disposal.
But if the ice bath is prepped according to above guides I'd suspect anything else before the ice bath. Haven't seen ice bath deviate more than 0.003C in my career if it is prepped properly.

Thank you for posting these.along with gravity.

Gee, you have got the gear to confirm your claims...lol. One thing I'd mention here is purity of water, can be a key consideration when best practices need to be employed. Some would agree that's all the time, others only as deemed necessary.

[Yuu]

If range is 0-100C, then any reason a Thermistor is not being used? They have a far greater value change across their working range and are very good in this temperature range IMO. Below is something I found online which is a good summary of why I ask.

No reason in particular. The pt100 stuff is just what I stumbled into learning about atm.
For my temp range, could a thermistor be more accurate? (yes I know an RTD is a type of thermistor technically but it's my understanding that thermistors in this context are typically semiconductor material with a negative temperature coefficient)
If so, any recommendations for like a stainless-steal-sheath probe preferably under $100?

I'm willing to bet, for this temp range, accuracy of thermistors and pt100 probes are comparable and it more primarily depends on how much you're willing to spend.
Like I think Fluke sells both types of probes with pretty darn good accuracy but they're expensive lol.

[jchw4]

No need to make it overly complicated if you don't work in primary laboratory with 10000 eur SPRT's
Properly prepared ice-water bath is easily better than 0,005 Cel accuracy and with some care 0,002Cel accuracy is quite possible. All you need is 10 eur thermos flask and 1 eur worth of distilled water. (ok, also some means to freeze the water but most of us have freezer)

+1

I don't have access to any serious gear, but a few years ago I bought  a 4-ch Omega thermometer from ebay for $20 (with thermocouples and case!).

So I decided to do an ice test. I looked at a Fluke youtube video about their lab and how they make their triple cells and decided to do some quick and dirty first experiment before trying to make distilled ice and so on.

I had:

• ~0.5L Thermos flask that I received as a swag (you can order these for $10 now starting from 1 item with custom labelling included!). Cannot be cheaper.
• Tap water.
• Tap water ice from the ice generator in my fridge. I guess most modern US fridges have it.
• 4 straws that I could fit my thermocouples. I terminated one end with some glue.

I just filled the flask to the top with ice, inserted straws and filled the rest with water. I also made some foam "lid" out of some random piece that I had around. I was afraid that it could freeze immediately because of the -18C in the freezer, but looking at the log it never happened.
So you can see that it went to zero in about 15 minutes. Note that thermocouples were sitting in an air-filled straws.

The log had all zeroes for about 6 hours, but then it went up 0.2-0.3 C . I guess that I incerted them too deep. Next day (~18 hours after start) I pulled straws up and it went back to 0 C for another 15 hours! So if I had not put the straws too deep, I could have 2 full days of 0C !

Note that even though the meter has specified accuracy of +/-1C and resolution of 0.1C, it stayed at 0.0...0.1 C for many hours!

After that I never tried going deeper with distilled water, proper ice/water balance and everything elese you see on youtube.

Just try yourself with the regular water and maybe adjust your experiment later if your gear has better stability than the simplest ice bath  Mine is clearly not good enough for that.

But if you post your results here, experienced folks could probably help you with improvements.

[jchw4]

BTW, could somebody suggest how to do a boiling water test? It feels way more complicated than the ice bath, but I was thinking of maybe getting current air pressure at my place from weather.com and adjusting readings to the boiling temperature table that I can probably find online.

Does it make sense to try that?

[mendip_discovery]

Too many variables with the boiling water technique.

What I have is a dry block calibrator and that is fairly good at holding temperature. But I use a master probe that is known and I can use that for the temperature. Expect me to revise this over the next year or so as I delve into the world of temperature.

[ap]

Building a gallium cell may also be an option for you...

[BarrowBoy]

Building a gallium cell may also be an option for you...

Unlikely..lol. Nice website BTW.

If range is 0-100C, then any reason a Thermistor is not being used? They have a far greater value change across their working range and are very good in this temperature range IMO. Below is something I found online which is a good summary of why I ask.

No reason in particular. The pt100 stuff is just what I stumbled into learning about atm.
For my temp range, could a thermistor be more accurate? (yes I know an RTD is a type of thermistor technically but it's my understanding that thermistors in this context are typically semiconductor material with a negative temperature coefficient)
If so, any recommendations for like a stainless-steal-sheath probe preferably under $100?

I'm willing to bet, for this temp range, accuracy of thermistors and pt100 probes are comparable and it more primarily depends on how much you're willing to spend.
Like I think Fluke sells both types of probes with pretty darn good accuracy but they're expensive lol.

It's actually a recommendation I was given by Fluke. Well not really Fluke, more their division based in Salt Lake City, formally known as Hart Scientific. Bang for Buck, it's a Thermistor solution. But over over 100C, or below TPW, and you need RTDS.  Here is a link for their premium Thermistor probes. Note the text at the foot of page. Also often thermistors are preferred due to their rate of change over the 0-100C span, but they can by design  a small sensor, with very fast settling time / stability, and very little stem convection, which improves accuracy when measuring and ease for calibration.

https://www.fluke.com/en/product/calibration-tools/temperature-calibrators/fluke-hart-secondary-thermistor-probes

Also this article may help, differs a bit from my advice on range, it notes (-80C thru +150C) which is news to me, but hey were here to learn

https://www.analog.com/en/resources/analog-dialogue/articles/thermistor-temperature-sensing-system-part-1.html