High accuracy digital thermometer

[EricTheRed]

For those using digital thermometers with .1° accuracy - would you mind sharing the make and model with me?

TIA

[TwoSheds]

I use a lot of items from Thermoworks for cooking and sometimes brewing:

https://www.thermoworks.com

The Thermapen remains the gold standard for quick reads but their probe based models are great. The Chef Alarm and wi-fi enabled Smoke are great for alarms.

Distilling I use Auber DSPR400 with PT100 probes built into the boiler or vapor path.

https://www.auberins.com/index.php?main ... cts_id=559

I'm also putting together a temp meter to monitor additional probes in the still:

https://www.auberins.com/index.php?main ... cts_id=618

But that one doesn't have the .1 accuracy.

Hope that helps, or at least gets the conversation rolling.

TwoSheds

[EricTheRed]

thanks
there are so many out there from cheap to hugely expensive!
Getting a list of those that those on this forum are happy with will make things easier.

Then it is just finding a supplier in RSA that can supply!

[Metalking00]

The probe type one i use for my reflux is a cheap no name one, but it seems relatively accurate. It reads boiling water as 100, and doesnt jump around.... i wouldnt mind having a nicer, higher accuracy one, but as long as it registers changes accurately im not worried if the actual numbers are correct.

I also have a ~$200 IR thermometer with variable emissivity settings, and a probe attachment. If you have an idea of the thermal emissivity of what youre measuring it is very fast and accurate, even from a ways away. I dont recall the brand or model at the moment, but if youre interested in such a thing ill go check.

[Demy]

I use a cheap thermometer and it is really accurate, I have compared it to 3 thermometers and it seems reliable. There are certainly better ones on the market

[Metalking00]

I have the suspicion that expensive thermometers are ofter cheap thermometers in disguise. I cant help thinking about a time i took apart a "made in USA" tool to find the parts inside stamped with "made in china"...

[EricTheRed]

but as long as it registers changes accurately im not worried if the actual numbers are correct.

That is precisely my aim - detecting the subtle changes in temp. The dial ones i have react slowly - too slowly for me

[Metalking00]

Im not sure exactly how quickly mine reacts., but it seems fast enough. I took it apart once and found the actual sensor is just sitting loosely inside the "outer probe", the metal spike part. I think that if the outer part could be filled with something more conductive, like the paste they use between computer chips and heat sinks, that it would improve responsiveness and accuracy a lot.

As far speed. When i use it with my boka it will register a large change in relix ratio within a few seconds, maybe 2?

[EricTheRed]

Im not sure exactly how quickly mine reacts., but it seems fast enough. I took it apart once and found the actual sensor is just sitting loosely inside the "outer probe", the metal spike part. I think that if the outer part could be filled with something more conductive, like the paste they use between computer chips and heat sinks, that it would improve responsiveness and accuracy a lot.

that is part of the problem with the ones i have. They have a copper/brass insert that you fit to the column, then insert the actual thermometer with a metal protrusion into it - so any changes in temp have to first affect the metal, then the metal probe before finally registering a change. Plus it is a pita to read at 2.1 meters off the floor!

Edit: - like this one

image.png

[Metalking00]

Like you say, my boka has a copper tube soldered into the column that the thermometer slides into. Its a close fit, but not perfect. It doesnt seem to cause problems. How instant of a reading do yoy need? I can see a mintue being an issue, but a few seconds is reasonable. Mine seems to react within a few seconds, even with the gap from column to probe and probe to sensor.

Thermal paste is cheap, and itd probably increase response considerably

[Metalking00]

I have one of those dial thermometers and i dont use it because its slow and very very jumpy. The jumpiness makes it unusable...

If your column is set up for that style thermometer, perhaps you could put a cork in its place and stick a spike-probe type digital through the cork so its in direct contact with the vapor. That'd eliminate one interface. Try out a cheap one like i or demy uses, it may be satisfactory.

[Salt Must Flow]

Im not sure exactly how quickly mine reacts., but it seems fast enough. I took it apart once and found the actual sensor is just sitting loosely inside the "outer probe", the metal spike part. I think that if the outer part could be filled with something more conductive, like the paste they use between computer chips and heat sinks, that it would improve responsiveness and accuracy a lot.

that is part of the problem with the ones i have. They have a copper/brass insert that you fit to the column, then insert the actual thermometer with a metal protrusion into it - so any changes in temp have to first affect the metal, then the metal probe before finally registering a change. Plus it is a pita to read at 2.1 meters off the floor!

Edit: - like this one

image.png

I make my thermowells like shown in this topic only I use this 4mm ID x 6mm OD copper tube. The ID of the tube fits 4mm RTD sensors, thermocouples and most thermometer probes perfectly.

I love this copper tube because it is very sensitive to temp change and the wall is only 1mm thick.

[EricTheRed]

Salt
Thanks for that

[Ben]

I second the Auberins units. High precision and can be calibrated, thermocouples are fluid and vapor proof.

[NZChris]

I use the cheapest LCD Digital Thermometer with a lead that I can get. A couple of dollars each, I buy them half a dozen at a time and use them for all manner of purposes, including the Bokakob head, and never noticed a problem with accuracy.

With the Bokakob, I don't need accuracy so much as I need the 0.1 resolution, as I only watch for temperature stability at the start and middle of the run, then for a 0.3 rise at the end.

[drmiller100]

I use a cheap thermometer and it is really accurate, I have compared it to 3 thermometers and it seems reliable. There are certainly better ones on the market

This. Then I calibrate in pure boiling water. I'm at 2800 feet above sea level so the numbers are off and barometric pressure changes can be noted.

The exact number isn't totally important.

You want repeatable not precise.

[TwoSheds]

This. Then I calibrate in pure boiling water. I'm at 2800 feet above sea level so the numbers are off and barometric pressure changes can be noted.

FWIW I've seen calibrating in an ice water bath recommended in some reliable sources as it doesn't vary with altitude the way boiling does.

[NZChris]

FWIW I've seen calibrating in an ice water bath recommended in some reliable sources as it doesn't vary with altitude the way boiling does.

Something I've never looked into is re-calibrating a thermometer to give me the boiling point/ABV relationship of a still charge when I'm distilling in the hills. I don't actually have any thermometers in those stills, but I would still be interested to know how accurately a thermometer that was re calibrated to read 212F/100C at, say, 3000ft, would agree with temperature/ABV tables at sea level.

[howie]

i use plastic cheap and nasty digital thermometers.
i don't care if they're not accurate, i only use them to observe temp changes.

[Hügelwilli]

Thermometers with a 0.1°C accuracy are very expensive and need maintenance. I would go a bit lower but then calibrate the whole system in place. Mount the sensor into your still, fully emerged in the vapor path and then distill water. There are calculators for the steam point of water at different pressure. Of course then the thermometer is well calibrated only for the still.

Why not in boiling water? Boiling water doesn't have a fixed temperature. The temperature of steam is much more fixed.

Why not ice water calibration? Because it is far away from our steam temperatures. A calibration in ice with a mediocre thermometer doesn't help much at 78°C.
But of course you can do a two point calibration, water steam and ice. But the ice-calibration is different because it doesn't happen in your still. So when water steam calibrating you take into account also factors like how much contact the sensor gets from outside the still via the sensor pod and the cables, and when ice-calibrating, you don't, the circumstances are different.
So probably the second calibration point should be ethanol steam instead of ice water. There are calculators with the aceotrope temperature at different pressures. But the problem is, that we don't have the real aceotrope at the top of our reflux stills, it is a bit lower in abv. But what does it to the temperature? Not much:
At normal pressure the aceotrope 97.2%abv has 78.17°C, 2%abv lower than the aceotrope is 78.4°C. So a good reflux still will probably have 78.3-78.4°C at the top at normal pressure.

I think the device from auber that TwoSheds mentioned, together with a Pt100 A 1/3 rating is a good choice. But it needs a calibration at least with water steam in place.

[drmiller100]

Boiling water doesn't have a fixed temperature. The temperature of steam is much more fixed.

Ummmm, what????

[Ben]

This is not that complicated. There is no need to try to figure out what your ethanol percentage boiling point vs atmospheric pressure is, or mess around with the math involved with figuring out what your steam temp is.

Look at your favorite weather app, find your barometric pressure and altitude. Plug it in to this calculator: https://www.thermoworks.com/bpcalc/ either calibrate your thermometer based on that, or note the difference. Or calculate your actual pressure and use a chart to determine your boiling point... these are known values.

Or use ice water. In the still you don't actually care what the temp is, you want precision (repeatability) in your thermometer from run to run. As long as the same thermometer reads the same in ice water every time you are likely good to go, your observations in the still behavior are valid from run to run. What's coming off the thermometer is just a number.

If you are talking about brewing/mashing its different, and making a double point calibration off of boiling and ice water makes sense.

[Hügelwilli]

Boiling water doesn't have a fixed temperature. The temperature of steam is much more fixed.

Ummmm, what????

Ummmm, yes!

I can measure very different temperatures in boiling water dependend on the distance to the heat source or the walls of the boiler or if I put a lid onto the boiler or not. A low tolerance PT100 and a device what costs new I think 200$.

And I am not the only one:
http://www.sites.hps.cam.ac.uk/boiling/index.htm
You should read not only thei but also all the links to experiments there. This knowledge is already 250 years old.
Some quotes:

However, happy-go-lucky sloppiness is not the most robust strategy of building scientific knowledge in the end, as the Royal Society Committee realized quite well. The committee's lasting contribution, the last of our three factors contributing to the fixity of the boiling point, was to find one clear method of reducing the variations of the boiling point due to miscellaneous causes. The following was the committee's chief recommendation: "The most accurate way of adjusting the boiling point is, not to dip the thermometer into the water, but to expose it only to the steam" (Cavendish et al. 1777, 845). Somehow, using the boiled-off steam rather than the boiling water itself seemed to eliminate many of the most intractable variations in the temperature:

"The heat of the steam therefore appears to be not sensibly different in different parts of the same pot; neither does there appear to be any sensible difference in its heat, whether the water boil fast or slow; whether there be a greater or less depth of water in the pot; or whether there be a greater or less distance between the surface of the water and the top of the pot; so that the height of a thermometer tried in steam, in vessels properly closed, seems to be scarce sensibly affected by the different manner of trying the experiment." (ibid., 824)

The recommendation to use steam came most strongly from Cavendish, who had already made the same proposal in his review of the instruments used at the Royal Society (Cavendish 1776, 380). But is the steam point really more fixed than the boiling-point? If so, why? (Read more about the fixedness of the steam point.)

[Hügelwilli]

This is not that complicated. There is no need to try to figure out what your ethanol percentage boiling point vs atmospheric pressure is, or mess around with the math involved with figuring out what your steam temp is.

Thanks for your opinion.

[drmiller100]

Boiling water doesn't have a fixed temperature. The temperature of steam is much more fixed.

Ummmm, what????

Ummmm, yes!

I can measure very different temperatures in boiling water dependend on the distance to the heat source or the walls of the boiler or if I put a lid onto the boiler or not. A low tolerance PT100 and a device what costs new I think 200$.

And I am not the only one:
http://www.sites.hps.cam.ac.uk/boiling/index.htm
You should read not only thei but also all the links to experiments there. This knowledge is already 250 years old.
Some quotes:

However, happy-go-lucky sloppiness is not the most robust strategy of building scientific knowledge in the end, as the Royal Society Committee realized quite well. The committee's lasting contribution, the last of our three factors contributing to the fixity of the boiling point, was to find one clear method of reducing the variations of the boiling point due to miscellaneous causes. The following was the committee's chief recommendation: "The most accurate way of adjusting the boiling point is, not to dip the thermometer into the water, but to expose it only to the steam" (Cavendish et al. 1777, 845). Somehow, using the boiled-off steam rather than the boiling water itself seemed to eliminate many of the most intractable variations in the temperature:

"The heat of the steam therefore appears to be not sensibly different in different parts of the same pot; neither does there appear to be any sensible difference in its heat, whether the water boil fast or slow; whether there be a greater or less depth of water in the pot; or whether there be a greater or less distance between the surface of the water and the top of the pot; so that the height of a thermometer tried in steam, in vessels properly closed, seems to be scarce sensibly affected by the different manner of trying the experiment." (ibid., 824)

The recommendation to use steam came most strongly from Cavendish, who had already made the same proposal in his review of the instruments used at the Royal Society (Cavendish 1776, 380). But is the steam point really more fixed than the boiling-point? If so, why? (Read more about the fixedness of the steam point.)

Thanks for your opinion. My experience is different.

[Hügelwilli]

Oh, I posted not only an opinion. I reported from my own experiments and linked to a website where you can read scientific evidence about this topic.

drmiller,
as always when you are posting you are only interested in fighting for your own opinions. Not a good method for improving.

[Twisted Brick]

Boiling water doesn't have a fixed temperature. The temperature of steam is much more fixed.

Ummmm, what????

Ummmm, yes!

I can measure very different temperatures in boiling water dependend on the distance to the heat source or the walls of the boiler or if I put a lid onto the boiler or not. A low tolerance PT100 and a device what costs new I think 200$.

And I am not the only one:
http://www.sites.hps.cam.ac.uk/boiling/index.htm
You should read not only thei but also all the links to experiments there. This knowledge is already 250 years old.

Excellent link, Hügelwilli. Looks like lots of good reading on Hasok Chang's site. Thanks for sharing.

[Hügelwilli]

Here a sketch of a two point calibration setup:

You see clearly that not the liquid but the steam is measured.
Those hypsometers were used originally for calculating the air pressure by measuring the temperature of water steam.

[NZChris]

At normal pressure the aceotrope 97.2%abv has 78.17°C, 2%abv lower than the aceotrope is 78.4°C. So a good reflux still will probably have 78.3-78.4°C at the top at normal pressure.

Which is exactly what my $2 LCD aquarium thermometer reads during a run.

[Metalking00]

Sometimes I, too, start to get wrapped up in the scientific minutiae of all the intricacies of this hobby. Then I remember I'm making whiskey in a bathtub...