Questions on pt100 probes - Page 1
Forum section: electronics / general

author: Yuu
author_rank: Regular Contributor
timestamp: July 05, 2024, 01:11:56 pm
content: Hello all,I'm going to put together a simple pt100 circuit with an ADS122C04 soon and I had some questions about pt100 probes.What is the best way to program resistance interpretations? There's really three things I could do:1. utilize 0.3850 ohm/C2. utilize polynomial fit (1 but more complex)3. use a lookup tableDownloading a pt100 csv table from fluke and comparing that to values obtained using 0.3850 ohm/C, I calculate at times an end temp difference of 0.38 C which is significant.So if I want this to be as accurate as possible over my temp range (0 to 100C) then it's clear options 2/3 are more accurate.Here's another thing I don't understand. They give these probes classifications and mine is a class A meaning\( \pm 0.15 C \pm 0.002 |T_C|. \)Does that uncertainty in temp assume the user is using the resistance measurements in one way or another? In other words, are they assuming you're using a linear fit or polynomial fit for ideal pt100 curve?

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 05, 2024, 02:15:41 pm
content: You might want to look up IEC 60751 which is the standard that defines them.0.15 + (0.002 x Temp °C) = Toleranceso0.15 + (0.002 x 100 °C) = 0.35 °CClasses are,AA = ± (0.1 + 0.0017 x °C)A = ± (0.15 + 0.002 x °C)B = ± (0.3 + 0.005 x °C)C = ± (0.6 + 0.01 x °C)Formulas for the calculating,For the range - 200 °C to 0 °C:$$ R_{t} = R_{0}[1+At+Bt^{2}+C(t-100 °C)t^{3} $$For the range of 0 °C to 850 °C:$$ R_{t} = R_{0}(1+At+Bt^{2}) $$where\$ R_{t} \$ is the resistance at the temperature \$ t \$;\$ R_{0} \$ is the resistance at \$ t = 0 °C\$The constants in these equations are:A = 3.9083 x 10-3°C-1B = -5.775 x 10-7°C-2C = -4.183 x 10-12°C-4EDIT: To clean up text and to fix errors.

author: Yuu
author_rank: Regular Contributor
timestamp: July 05, 2024, 04:31:11 pm
content: Ahh okay. So they make their table with the following polynomial fit for ideal pt100 curve:\[ R_t = R_0 (1 + At + Bt^2)\]and that's also how they "interact" with their tolerance for the 0 to 850 C range.Meaning, given a measured resistance, you calculate temp using either a lookup table (generated from above) or via math. Then, for that calculated temp, the actual temperature should be \(\pm (0.15 + 0.002 \cdot |T|)\) for Class A. Where that uncertainty stems from the fact the probe isn't an ideal pt100 probe (e.g. may contain impurities) and its resistance curve may drift from the ideal curve.

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 05, 2024, 05:06:52 pm
content: I would think of it as the probe tolerance, much like a resistor rather than an uncertainty. However, it would make up a part of an uncertainty if you were to try and account for most of the errors in the system. Probe + reader etc.

author: EC8010
author_rank: Frequent Contributor
timestamp: July 05, 2024, 05:14:29 pm
content: Exactly what I was going to say. It's a resistor. I had a couple of Farnell 219-1840 Class A PT100 probes measured for resistance at the triple point of water and whilst they were within 0.4% of 100 ohm, they weren't spot-on. That tolerance is probably the major player in the uncertainties.Interestingly, the triple point of water is determined acoustically - at that temperature there are crackling noises. One day, that might be the deciding point in a pub quiz. Probably need to be a pub near a scientific establishment, though.

author: Yuu
author_rank: Regular Contributor
timestamp: July 05, 2024, 07:12:49 pm
content: Quote from: mendip_discovery on July 05, 2024, 02:15:41 pmI'm seeing negatives in front of B and C, see attachment.Hehe, you know it sucks I can't access probably more up-to-date standards without paying for them for some reason. Who does that??? That's like me having to use "alternate methods" to access research papers because journals want to charge you even though you know they get enough fake money from universities anyway.

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 05, 2024, 07:37:59 pm
content: Oops, my mistake. I missed that bit when typing it up.It's scary how expensive standards are, especially when you are just looking. I findpdf's while having acoffee.comhandy for that. However, I usually end up buying them in the end as it is for work.

author: Sensorcat
author_rank: Regular Contributor
timestamp: July 05, 2024, 08:38:54 pm
content: Quote from: EC8010 on July 05, 2024, 05:14:29 pmOne thing to consider is that this measurement is not easy. For an accurate result, one has to:Reach the triple point.Maintain that point, at least for one integration interval.Make sure that the resistor grid is at the same temperaure of the water, even though there is a barrier between both, which has thermal resistance.Make sure that the resistor grid is at the same temperaure of the water, even though there is an electrical connection to the outside, which also conducts thermally.Take self-heating of the resistor into account.Preferably use Kelvin-connection, since the other constraints favor long electrical connections.Since I don't know your work, I'm not saying that you did not achieve a very accurate measurement. But even the first condition alone is tricky: How do you make sure that your entire water reservoir is at triple point? How do you detect if slight variations in water temperature exist inside the reservoir? If you detect the triple point, how do you know which part of the water body has it? Did you have access to a proven triple-point cell for the measurement?

author: mzzj
author_rank: Super Contributor
timestamp: July 05, 2024, 08:43:00 pm
content: Quote from: EC8010 on July 05, 2024, 05:14:29 pmtemperature is not determined acoustically, only the physical integrity or level of vacuum in the triple point cell.Triple point cell makes nerve-wracking cracks and clicks if you "slosh" the water inside it but it happens also at room temperature.Once triple point conditions have formed inside the cell and the ice is annealed it sits quietly without making any noise.

author: mzzj
author_rank: Super Contributor
timestamp: July 05, 2024, 08:47:32 pm
content: Quote from: Sensorcat on July 05, 2024, 08:38:54 pmNo need to make it overly complicated if you don't work in primary laboratory with 10000 eur SPRT'sProperly 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)

author: Sensorcat
author_rank: Regular Contributor
timestamp: July 05, 2024, 09:20:24 pm
content: Quote from: mzzj on July 05, 2024, 08:47:32 pmI have measured 1°C temperature differences in an ice-water bath, perhaps more. It's a myth that an ice-water bath as such has uniform temperature. There's gravity and convection, and there is a surface and a bottom, wich means that an open bath has no thermal symmetry. How do you prepare your bath to get this surprising accuracy? And how do you verify that? Now irony intended, if you have a way to reach that accuracy with simple means, and proper verification, I would like to learn how. Please note that I view this from an industrial perspective, which means you have to put your claims into a data sheet, and if it's wrong, an unsatisfied customer is the minimum consequence.

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 05, 2024, 09:29:04 pm
content: Quote from: Sensorcat on July 05, 2024, 09:20:24 pmI know a lab near to me that has 17025 for temp and they use the ice in a thermos perfectly fine for 0.035 °C k=2 at 0 °C. I don't have 17025 yet but I have an IsoTech Venus with the ability to do -55 °C to 140°C. Its my project for the next year, when I am not onsite.

author: mzzj
author_rank: Super Contributor
timestamp: July 05, 2024, 10:33:55 pm
content: Quote from: Sensorcat on July 05, 2024, 09:20:24 pmEasy, fill the whole container with crushed ice and some water, making sure that ice is not floating on top of water. Or if there is water layer in the bottom don't insert your thermometer so deep that it reaches water-only part of the bath.(Alternatively use circulating mixer)NIST, BIPM and NZ national standards labs have some good guides:https://www.measurement.govt.nz/resources/#collapse-control-1-5https://nvlpubs.nist.gov/nistpubs/Legacy/TN/nbstechnicalnote1411.pdfhttps://www.bipm.org/documents/20126/41773843/Specialized-FPs-above-0C.pdf/10265617-c79f-0ea5-8da9-8d359e21c6beIf 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.

author: mzzj
author_rank: Super Contributor
timestamp: July 05, 2024, 10:35:32 pm
content: "The melting point of water is a very simple, effective and inexpensive temperaturereference. As shown in Figure 12, the melting point of pure water at atmosphericpressure of 101325 Pa is near 0.0024 C. However, this is not the ice point as it is usedas a temperature reference. The practical ice point is the equilibrium temperature of iceand air-saturated water, which occurs at a pressure of 101.325 kPa at the lowertemperature of 0.0 C almost exactly. The 0.0024 C difference is caused by dissolvedair in the water and ice.Historically the ice point was the defining point for many temperature scales untilthe more precise water triple-point cells were developed. It still has a major role inthermometry since it is a fixed point that can be readily achieved by almost anylaboratory with a minimal cost. The main advantage of the ice point is that it can bemade very simply and cheaply and, so long as the basic principles are followed [ASTM2002, Nicholas and White 2001], it is relatively easy to achieve uncertainties of 10 mK,and with a little care it can be realised with an uncertainty of 1 mK, and with great carewith an uncertainty of about 100 K [Harvey et al. 2012]."

author: Yuu
author_rank: Regular Contributor
timestamp: July 05, 2024, 11:00:58 pm
content: Quote from: mzzj on July 05, 2024, 10:33:55 pmThank you for posting these.

author: Sensorcat
author_rank: Regular Contributor
timestamp: July 05, 2024, 11:34:02 pm
content: Quote from: mzzj on July 05, 2024, 08:47:32 pmSome quotes from the third document you linked:QuoteQuoteQuoteYeah, easy. 11€. If we get to know what compressing quite firmly is, we can do that on the kitchen table, and guarantee not to exceed 5mK error. Just that we don't know what we have, unless we can practice with a proven standard, which exceeds the BOM of 11€ quite a bit.

author: mzzj
author_rank: Super Contributor
timestamp: July 06, 2024, 07:57:47 am
content: YMMV. Opinions and experiences wary from your 1000mK to 0.1mKIn my experience ice bath compaction or fine ice is not that critical if you have enough immersion depth. 30xD or 40xD usually takes care of that.And we use "Slush method" mentioned in next chapter that is not so picky about ice fineness or compaction.Contamination and water purity is critical point but easily taken care by using distilled water and not washing your face with the ice bath.Typical tap water around here has ~5mK lower freezing point due to dissolved salts.

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 06, 2024, 09:19:38 am
content: Also worth reading is,Euromet Guides - No. 13 | Guidelines on the Calibration of Temperature Block Calibrators | TC-T | Version 4.0, 09/2017https://www.euramet.org/publications-media-centre/calibration-guidelinesWhile it is easy to do the maths to go from Temp to Ohms, doing the ohm to temp is another issue. I like maths but I don't know it well enough to work out the best way to do it, and of course any documentation I find is always assuming I understand coding and maths to a level beyond my comprehension.

author: EC8010
author_rank: Frequent Contributor
timestamp: July 06, 2024, 09:30:54 am
content: OK. Two posters have queried a couple of my comments. Fair enough. I had my two PT100 sensors calibrated at water triple point in a calibration laboratory. I know they had in-calibration 3458A available (and almost certainly used) but I didn't make a note of the water bath apparatus used (which I was shown). In discussion with the head of the laboratory, he mentioned the crackling. Perhaps I misinterpreted his comment, but I took it to mean that the crackling was an indication that the triple point had been achieved. I know for sure that the PT100 connection was a Kelvin connection since I provided that. I assume that (as a calibration laboratory) that they knew that considerable time is required to achieve stability. Hope that helps.I shall read the ice bath preparations - then I can do a calibration good enough for my needs at home.The various comments made have reaffirmed my conviction that it's quite difficult to measure temperature accurately. I glue small PT100 sensors to whatever I want to measure and make an effort to keep the glue film as thin as possible because of the temoperature drop across it. I also insulate the outside of the sensor to maximise thermal resistance to the environment to minimise the thermal potential divider effect. But in doing so, I must slightly change the cooling of the measurand. Like I said, measuring temperature is tricky. But whilst my measurements may not have perfect accuracy, they do reveal small changes repeatably, and that's often more important.

author: nfmax
author_rank: Super Contributor
timestamp: July 06, 2024, 09:48:26 am
content: Quote from: mendip_discovery on July 06, 2024, 09:19:38 amA recommended way to do this is given in Nicholas & White on page 242. They use a recursive technique: an initial approximate solution is improved by repeated application of a 'polishing' function.Given a measured resistance ratio W(t), i.e. the ratio of the measured resistance to the resistance at 0˚C (nominally 100Ω, but you can use a measured calibration value) and the PRT100 formula constants A, B, and C, calculate an initial temperature estimate t0 (in ˚C) using the quadratic formula on the equation:W(t) = 1 + A*t0 + B* t0^2Then use the calculated t0 to calculate t1:t1 = (W(t) - 1)/(A + B*t0 + C*t0^2*(t0 - 100))(the C term is only required if t0 > 0 ˚C)For 'normal' temperatures, one application of the iteration is 'good enough', but you can repeat it to claculate t2 in terms of 1, etc.This is simple enough to set up in Excel: then you can play with it and compare the results with published PRT tables, to convince yourself it works!

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 06, 2024, 12:56:33 pm
content: Well I have got the maths working, it's not neat but it does the job. I just did a loop until it gets the same value as the resistance. I am sure there is a better way to do it but meh.@YuuI will post the maths to github as I used python to do it and you can use what you need to do what you need. I am still playing with it at the moment so I will post later.My motivations is partly due to the MD at work telling me that he would like me to get 17025 accreditation for temperature so I am interested in the maths as well.

author: mzzj
author_rank: Super Contributor
timestamp: July 06, 2024, 04:03:08 pm
content: Quote from: mendip_discovery on July 06, 2024, 09:19:38 amI have used approximate inverse function of the reference function. Was fairly straightforward task to do even with excel and the 6th degree function I have been using is accurate to 0,003mKmOhm.For some reason there is no commonly used or "approved" inverse polynomial function for IEC60751. (ITS-90 SPRT's and thermocouples have published reference functions and their inverse polynomials)Not the best way to do it on small microcontroller but even slowly 8 bit AVR can crank the 6-th degree polynomial probably in 10-20milliseconds.

author: Yuu
author_rank: Regular Contributor
timestamp: July 06, 2024, 04:03:51 pm
content: Quote from: mendip_discovery on July 06, 2024, 12:56:33 pmOh cool. Thanks. It'll probably be a week or two until I get the pcbs, get them soldered, etc... etc.. but I'll let you know what I end up doing when programming the calculations. I'm pretty good at math so hopefully it'll turn out nice hehe.

author: TUMEMBER
author_rank: Regular Contributor
timestamp: July 06, 2024, 04:25:16 pm
content: SensorcatYou 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.

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 06, 2024, 06:27:24 pm
content: For those that are interested,https://github.com/mendip-defender/conversion_calculators/It is not perfect, but its better than nothing.I need to learn how to make interactive Jyputer Notebooks that way people can play with it a little more.Note: Already updated to correct a small error > to a >=

author: Sensorcat
author_rank: Regular Contributor
timestamp: July 06, 2024, 08:16:06 pm
content: Quote from: TUMEMBER on July 06, 2024, 04:25:16 pmAlthough 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/

author: MiDi
author_rank: Frequent Contributor
timestamp: July 06, 2024, 08:26:48 pm
content: Quote from: TUMEMBER on July 06, 2024, 04:25:16 pmStandards Lab NZ Document

author: Yuu
author_rank: Regular Contributor
timestamp: July 07, 2024, 09:45:19 pm
content: 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 itNicholas J V and White D R (2001) Traceable Temperatures: An Introduction toTemperature Measurement and Calibration (John Wiley and Sons, Chichester).

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 07, 2024, 09:48:46 pm
content: Traceable Temperatures, produced by Wiley.Physical copies are hard to come by.

author: arvee
author_rank: Contributor
timestamp: July 09, 2024, 10:27:46 pm
content: Hi,Fluke has a webpage for the PT100https://us.flukecal.com/pt100-calculatorHere is my calculator in HTML.Details of the Newton root iteration be found in the comments of the calculator.RV

author: BarrowBoy
author_rank: Contributor
timestamp: July 09, 2024, 11:42:24 pm
content: 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.

author: BarrowBoy
author_rank: Contributor
timestamp: July 09, 2024, 11:52:30 pm
content: Quote from: Yuu on July 05, 2024, 11:00:58 pmGee, 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.

author: Yuu
author_rank: Regular Contributor
timestamp: July 12, 2024, 06:26:17 pm
content: Quote from: BarrowBoy on July 09, 2024, 11:42:24 pmNo 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.

author: jchw4
author_rank: Regular Contributor
timestamp: July 13, 2024, 10:27:33 am
content: Quote from: mzzj on July 05, 2024, 08:47:32 pm+1I 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 bathMine is clearly not good enough for that.But if you post your results here, experienced folks could probably help you with improvements.

author: jchw4
author_rank: Regular Contributor
timestamp: July 13, 2024, 10:37:21 am
content: 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?

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 13, 2024, 12:57:43 pm
content: 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.

author: ap
author_rank: Frequent Contributor
timestamp: July 13, 2024, 02:30:15 pm
content: Building a gallium cell may also be an option for you...

author: BarrowBoy
author_rank: Contributor
timestamp: July 14, 2024, 10:16:27 am
content: Quote from: ap on July 13, 2024, 02:30:15 pmUnlikely..lol. Nice website BTW.Quote from: Yuu on July 12, 2024, 06:26:17 pmIt'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-probesAlso 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 learnhttps://www.analog.com/en/resources/analog-dialogue/articles/thermistor-temperature-sensing-system-part-1.html

author: mzzj
author_rank: Super Contributor
timestamp: November 09, 2024, 08:55:44 pm
content: Quote from: jchw4 on July 13, 2024, 10:37:21 amBit late to the party but for anyone interested try digging old NIST documents. Previous temperature scale IPTS-68 (used up to 1990) was based on water boiling point and some laboratories had specific apparatus for water boiling point calibration.IIRC you can't immerse the thermometer to boiling water, instead you need to form closed space for the steam to collect and heat up the thermometer with the steam.And be vary of the air pressures. Most weather services and all airports give you "sea level adjusted" barometric pressure that can be totally different from true air pressure.An extreme example would be Albuquerquehttps://photovoltaics.sandia.gov/weather/Weather.htm

author: MiDi
author_rank: Frequent Contributor
timestamp: December 01, 2024, 10:48:15 am
content: Quote from: jchw4 on July 13, 2024, 10:37:21 amAs for ice bath you need pure water e.g. deionized (standard labs use VSMOW2), an accurate abs. pressure sensor e.g. BMP581 and the calculatorcoolpropfor BPW at the measured pressure.