Temp measurement and accuracy

[swmcl]

Hi all,

I have been stuggling with temp measurement. I started out with a cheaper ($200 - China) multimeter with temp probe. Then I borrowed a little solid temp probe from work that had a long straight metal shaft with the probe inside. This second probe read 2.3 degrees C different to the original. I then thought I'd buy a thermometer from B&H (the Patterson one) with as much accuracy as possible (0.1 degree graduations). Alongside that purchasing decision, I went and bought a calibrated multimeter as well (an expensive Extech 570A which is really 'accurate' ...) (This mulitmeter will replace the other Chinese one for all functions - it aint just a temp meter !)

The Extech and the thermometer are about 1.5 degrees C different. The Extech and the original Chinese one are about 2.5 degrees C different. The Extech is reading similar to the probe from work.

Which one do I trust ?? Just how accurate are the thermometers ?? I know the thermometers are certainly slower to repond to variations.

Given that 1 degree matters in processing ...

Cheers,

Steve

[Vaughn]

It does not matter how accurate they are (at least within several degrees of "normal"), as long as they have good precision. In other words, as long as they give the same temperature under the same circumstances every time.

Do all your work and testing with the one thermometer and you are set. If you get another thermometer, calibrate it to your original.

Vaughn

[Leigh]

Hi Steve,

I expect your multimeters are using Type K thermocouples, since those are most common and cheapest.
Consumer-grade Type K thermocouples have a rated accuracy of ±2.5°C (~5°F).

Even the best laboratory-grade Platinum thermocouples are only rated ±1.0°C (~2°F).

======

I just looked through the offerings at McMaster-Carr. They have quite a selection.
The one I would get is catalog nr 3569K58 at $53.92.
It's rated accuracy is ±0.4°F (~0.2°C). It comes with an NIST certificate of calibration, so you know it's right.
It looks like this: 70763 The site is http://www.mcmaster.com
Great folks to deal with. No minimum order and no handling charges, just actual shipping.

======

You can calibrate any thermometer that has sufficient range (some have a very narrow range of readings).

Mix up some ice water (preferably distilled water for both) in an insulated cup. Swirl it around to make sure
it's reached equilibrium. The thermometer should read 0°C or 32°F.

Put some distilled water into a pot and bring it to a good rolling boil. Your reading should be 100°C (212°F).

While distilled water is not essential, any significant mineral content or contamination
may change the actual temperatures from the ideal.

- Leigh

[Jay DeFehr]

I've only recently re-acquired a thermometer, previously using my finger with no ill effects, but then I only "measured" the water, and not the mixed developer. Of all the tests people seem willing to perform, it's rare anyone tests the degree of precision necessary for their process. I'm speaking of myself here, and not being critical of anyone else. Now that I have a thermometer again, I use it.

[tgtaylor]

Steve,

Leigh's suggestion of how to calibrate the thermometer seems correct to me - at least that is how I vaguely remember calibrating the thermometer in college. I currently use two Jobo thermometers that came with the CPA-2: one reading in degrees Centigrade and the other in degrees Fahrenheit and both read identical. I set my Patterson adjustable to the Jobos and all three read identical so I am comfortable with their readings. That said I always check the Patterson to the Jobo as it is fairly easy to knock the former out of adjustment - which is the reason for the included wrench.

Thomas

[Joe O'Hara]

A couple of issues here. When a thermometer is said to be able to read to 0.1 deg F (or C), that is what is called "resolution". Resolution is just how precisely you can read it. It says nothing about how close the reading is to an accepted temperature standard. The latter is "accuracy". If you take a random thermocouple or thermistor-type probe and connect it to a multimeter, no matter how many digits it has to the right hand side of the decimal point, that will not guarantee an "accurate" reading if the probe is not calibrated (i.e., adjusted or measured against a standard). Your experience in getting readings to within a couple of degrees is what I would expect from devices like that. As Vaughn stated, for B/W work, reproducibility is more important than accuracy. Plus or minus a degree or so is OK, just tinker with the times until you get negatives you like. For color, it is a different story. To get a calibrated lab thermometer that will get you within 0.25 deg F will cost you about $85 the last time I checked. That was too much for me so I bought 5 different fever thermometers and calibrated my dial thermometer with the average of those at 100 deg F, which is within their specified range and exactly where C-41 wants to be. It is unlikely to be more than 0.5 deg F off unless I'm really unlucky. I'd be suspicious of the boiling-water or ice-water methods since (1) the boiling point of water is affected by atmospheric pressure and (2) unless you develop your film at 32 F or 212 F there's no assurance that you won't be off be a degree or more at your working temperature due to linearity errors in your thermometer (especially if it is one of the electrical kinds). Bottom line: the man who has one thermometer knows what the temperature is; the man with two is never sure.

[Shen45]

Hi all,

I have been stuggling with temp measurement. I started out with a cheaper ($200 - China) multimeter with temp probe. Then I borrowed a little solid temp probe from work that had a long straight metal shaft with the probe inside. This second probe read 2.3 degrees C different to the original. I then thought I'd buy a thermometer from B&H (the Patterson one) with as much accuracy as possible (0.1 degree graduations). Alongside that purchasing decision, I went and bought a calibrated multimeter as well (an expensive Extech 570A which is really 'accurate' ...) (This mulitmeter will replace the other Chinese one for all functions - it aint just a temp meter !)

The Extech and the thermometer are about 1.5 degrees C different. The Extech and the original Chinese one are about 2.5 degrees C different. The Extech is reading similar to the probe from work.

Which one do I trust ?? Just how accurate are the thermometers ?? I know the thermometers are certainly slower to repond to variations.

Given that 1 degree matters in processing ...

Cheers,

Steve

Ancient photographic saying --" Man with 2 thermometers is never sure what the temperature is, man with one thermometer is blissfully unaware what the real temperature may really be."

For B&W Vaughn's advice is exactly correct.

[Heroique]

It does not matter how accurate they are ... as long as they have good precision. In other words, as long as they give the same temperature under the same circumstances every time.

I like what Vaughn says, so let’s give it give it an example:

If you like results when your thermometer reads “68 F,” then you want to be sure that each time your thermometer says “68 F,” you're getting that very same temperature from job to job – even if it might be different than the “real” temperature.

What makes inferior thermometers so exasperating is that w/ each indication of, say, “68 F,” you may actually be getting varying temperatures. Maybe 67 for one job, and 71 for another, even though your thermometer always says 68…

I like dial (analog) thermometers, but I’ve noticed they have a tendency to vary w/ barometric pressure changes! Maybe the better dial thermometers don't do this.

[Doremus Scudder]

Many good labs keep an expensive calibrated thermometer in a safe place to check other thermometers against occasionally and make adjustments.

I've got an old Kodak Process Thermometer that I use for that purpose and a few of the Kodak color thermometers as well. They all seem to read within less than 0.5°C of each other.

The analogue dial thermometers are another story. I've got stickers on them telling me the error at my processing temperature (e.g., "reads +2°F") for the ones with no adjustment. For the others that can be twisted to adjust the reading, I adjust against the process thermometer at processing temp. If it's wrong, at least I'm consistent. :rolleyes:

Acquiring a good, calibrated thermometer (the one Leigh suggests would be fine if it is that accurate through its entire range) and using that to calibrate other thermometers to.

BTW, there are lots of other threads on this topic here. Do a search for even more than you wanted to know.

Best,

Doremus

[E. von Hoegh]

Hi all,

I have been stuggling with temp measurement. I started out with a cheaper ($200 - China) multimeter with temp probe. Then I borrowed a little solid temp probe from work that had a long straight metal shaft with the probe inside. This second probe read 2.3 degrees C different to the original. I then thought I'd buy a thermometer from B&H (the Patterson one) with as much accuracy as possible (0.1 degree graduations). Alongside that purchasing decision, I went and bought a calibrated multimeter as well (an expensive Extech 570A which is really 'accurate' ...) (This mulitmeter will replace the other Chinese one for all functions - it aint just a temp meter !)

The Extech and the thermometer are about 1.5 degrees C different. The Extech and the original Chinese one are about 2.5 degrees C different. The Extech is reading similar to the probe from work.

Which one do I trust ?? Just how accurate are the thermometers ?? I know the thermometers are certainly slower to repond to variations.

Given that 1 degree matters in processing ...

Cheers,

Steve

First, as long as the thermometer will repeat, it's good to go.

Second, with your thermocouple probe, it's easy to check it at two points. A beaker of icewater will stabilise at 0C until all the ice melts. A pot of water boiling at sealevel will stabilise at 100C. If you are not at sealevel, find your altitude on a map and google the boiling point for that altitude (and your current barometric pressure).

Virtually any thermometer can be checked at 0C, not all will go to boiling point.
I have a certified calibrated mercury thermometer to check my other thermometers.

[tgtaylor]

I just checked my therometers and the Jobo "color" therometer reads 18.6C (65.48F) and the Jobo "B&W" reads 65.5F. Both are of the mercury type in glass tubes and are kept together. The Patterson dial theromenter read ~65.3F but is was stored inside a cabinet away from the 2 Jobo's but in the same room. Since I live at sea level I instinctively trust the Jobo readings which I use to calibrate the Patterson's. Guessing the temperature with your finger I have found to be several - as much as 10 degrees off mark. Your nose would make for a better probe as it is more sensitive than the finger.

Judgng from the replies it looks like I lucked out and got 3 good therometers:)

[Bruce Watson]

I have been struggling with temp measurement.
.
.
.
Which one do I trust ?? Just how accurate are the thermometers ?? I know the thermometers are certainly slower to repond to variations.

You can only trust the precise ones. That is, the ones that are repeatable. They may not be terribly accurate, but if they are within a degree or two they should work fine for photography.

Now, pick one and get rid of the rest. Comparing thermometers will drive you crazy.

[swmcl]

Vaughn, I know you are correct and I do appreciate your reply.

Thanks Leigh for your insights. This thermometer is not able to go below 15C so I can't do the iced water trick. Plus I'm 600m above sea level for the 100C as well ... I might go the McMaster one though ... I should've mentioned the new Extech multimeter is NIST calibrated. McMaster-Carr seems to only ship to the US ... dumb heh!

Bruce ... I'm building a precessing tank on the side. One that is like a big Jobo. I need to find something accurate and repeatable for when I eventually get the project up and running. The project uses thermistors which can also theoretically offer a great resolution.

Thanks all !

(Now I need to find a way of getting the McMaster-Carr probe to Australia ... anyone got a PayPal account with the inclination ? )

[Leigh]

(Now I need to find a way of getting the McMaster-Carr probe to Australia ...
Hi Steve,

I have an open account with McM, so no problem getting the thermometer.

Don't know how much it would cost to ship it and such.

- Leigh

[photobymike]

i use a Kodak Process Thermometer either a type 2 or 3 ... i prefer type 2... I like to buy on ebay but they always send us mail. Besides getting broken the USPS specifically lists the them as hazard and forbids them in the mail system. Ten thousand dollar fine and responsible for clean up is what they say on there website....i have 3 broken when i have received them. Well anyway they are accurate.

[Jim Jones]

Many good labs keep an expensive calibrated thermometer in a safe place to check other thermometers against occasionally and make adjustments.

I've got an old Kodak Process Thermometer that I use for that purpose and a few of the Kodak color thermometers as well. They all seem to read within less than 0.5°C of each other.

The analogue dial thermometers are another story. I've got stickers on them telling me the error at my processing temperature (e.g., "reads +2°F") for the ones with no adjustment. For the others that can be twisted to adjust the reading, I adjust against the process thermometer at processing temp. If it's wrong, at least I'm consistent. :rolleyes:

Acquiring a good, calibrated thermometer (the one Leigh suggests would be fine if it is that accurate through its entire range) and using that to calibrate other thermometers to.

BTW, there are lots of other threads on this topic here. Do a search for even more than you wanted to know.

Best,

Doremus

Yes, indeed. Analog dial thermometers should be checked often against a reliable meter. If they are stored together in a darkroom with stable temperature, this is easy to do at room temperature whenever you use the dial thermometer. Keeping the darkroom, chemicals, film tanks, and wash water at the desired developing temperature saves a lot of bother.

[swmcl]

Leigh,

It doesn't matter much ... if McMaster is the only place we know of then the cost must be borne ...

I'll send a PM to discuss further ..

Cheers,

Steve

[Drew Wiley]

Certified thermometers can be obtained from just about any serious lab supply firm, typcially for around $250. Just be sure it's a model optimized for the mid-ranges typical of photo processes. I personally use the Kodak Process Thermometer Type II. Never had good luck with electronic probes due to slow response times. McMaster sells direct to end
user with a credit card. I'd probably try Lab Safety Supply first.

[Louie Powell]

It does not matter how accurate they are (at least within several degrees of "normal"), as long as they have good precision. In other words, as long as they give the same temperature under the same circumstances every time.

Do all your work and testing with the one thermometer and you are set. If you get another thermometer, calibrate it to your original.

Vaughn

Vaughn has the right idea, but it's not expressed clearly.

The issue isn't precision. The term 'precision' refers to the 'fine-ness' of the measurement. A thermometer that measures to 0.1 deg us sufficient for photochemical processing.

The critical issue that Vaughn meant to say is 'repeatability'. That is, if the liquid is 100deg, then the thermometer should register 100 deg every time it measures the temperature of that liquid.

The third measurement concept is 'accuracy' which refers to how closely one instrument compares to an absolute reference instrument. Accuracy is important to achieve predicable results, but the photochemical process does allow for minor variations in temperature if compensating changes are made in time.

But as Vaughn said, of the three concepts - precision, accuracy and repeatability - the most important is repeatability because if your thermometer is repeatable, then the results that you will achieve will be both predictable and repeatable. No one cares about how accurately you measured the temperature of your processing solutions - all they care about is whether your negatives are properly developed.

[Leigh]

...of the three concepts - precision, accuracy and repeatability - the most important is repeatability...
Absolutely correct.

As long as a thermometer gives you the same reading every time for a given temperature,
it will work fine for process control.

Any actual error between what the thermometer says and the true temperature will be compensated automatically
when you calibrate your process. We all calibrate our development process, yes?

- Leigh

[Vaughn]

Thanks for the info, Louie. I have always seen it as it relates to target shooting (which I do not do, so chances I am wrong with this, too).

Accuracy is hitting the bullseye, precision is a good grouping (shades of "Young Frankenstein", LOL!)

Vaughn

PS -- here at the university, we have a bunch of dial thermometers. I "calibrate" them all from the built-in sink thermometer. Accurate? I do not know, but all our dial ones read the same! (for awhile, anyway!)

[Heroique]

For perfect clarity, we need an example where the thermometer is repeatable, but neither accurate nor precise. ;^)

[Drew Wiley]

Depends what you are doing. Repeatability is always critical, accuracy sometimes is. No
different from a measuring graduate or weighing scale in this respect - for some formulas
you need to be spot on, for others ... But as far as Vaughn's analogy goes, that's why
they invented shotguns

[Leigh]

For perfect clarity, we need an example where the thermometer is repeatable, but neither accurate nor precise.
That's easy.

A good dial thermometer (very repeatable)
where the dial has been turned 90° from its proper position (quite inaccurate),
and only has temperature lines at 20°C increments (very imprecise).

- Leigh

[rdenney]

That's easy.

A good dial thermometer (very repeatable)
where the dial has been turned 90° from its proper position (quite inaccurate),
and is only calibrated in 10°C increments (very imprecise).

- Leigh

Better yet, a thermometer with no scale at all.

Rick "accuracy=0, precision=0, highly repeatable" Denney

[tgtaylor]

This is not 1812 but 2012 and the thermometer has been around for a long time now, is sophisticated, and inexpensive. I just placed my 4 therometers side by side for a comparison and the 2 Jobo's and Patterson Dial read identically - 65F; the small probing thermometer for cooking read 66F. While I'm not the betting type, I'd wager that the former 3 are within 1 degree of "true accuracy."

Thomas

[Leigh]

The following will serve to define the three parameters under discussion...

Precision:
The granularity of the measurement, i.e. how small an increment can be detected and displayed.
This is a function of the measurement technology used and of the method used to display the value.
E.g. if you stick your arm out the window, you can tell how warm the air is, but with very low precision.

Accuracy:
How close the reading is to the true value of the parameter.
Stated another way, it's the magnitude of the error, less error = more accurate.
For example, measuring air that's 20.0°, a reading of 20.1° is more accurate than a reading of 21.0°.

Repeatability:
When you take ten readings of the same thing, they should all be exactly the same. This is perfect repeatability.
The extent to which they differ is a measure of the repeatability. The greater the variation the worse the repeatability.
In target shooting this is the size of the group of holes in the target... smaller is better.

HTH

- Leigh

[Leigh]

Better yet, a thermometer with no scale at all.
Lacking a scale, the instrument could not properly be called a thermometer.

It could be a strain gauge.

- Leigh

[Leigh]

...I'd wager that the former 3 are within 1 degree of "true accuracy."
Disregarding some very odd and unlikely source of error, I would agree.

As a practical matter, any thermometer that is accurate within one degree is certainly satisfactory for photographic work.

- Leigh

[Drew Wiley]

Junk is junk, and there are a lot of junky thermometers out there. Does this matter? Maybe
not for garden-variety black and white work, but just try something like color separation
negatives, which have to match precisely between processing cycles. And I certainly wouldn't trust ANY dial thermometer or chepie mercury unit for that kind of thing.

[Heroique]

Okay, I think we’re all on the same page about the three parameters, but just for fun:

What would an archer’s target look like if, say, three shots proved repeatable – but were not accurate or precise?

[E. von Hoegh]

The following will serve to define the three parameters under discussion...

Precision:
The granularity of the measurement, i.e. how small an increment can be detected and displayed.
This is a function of the measurement technology used and of the method used to display the value.
For example, if you stick your arm out the window, you can tell whether the air is hot or cold, but with very low precision.

Accuracy:
How close the reading is to the true value of the parameter.
Stated another way, it's the magnitude of the error, less error = more accurate.
For example, measuring air that's 20.0°, a reading of 20.1° is more accurate than a reading of 21.0°.

Repeatability:
When you take ten samples of a reading, they should all be exactly the same. This is perfect repeatability.
The extent to which they differ is a measure of the repeatability. The greater the variation the worse the repeatability.
In target shooting this is the size of the group of holes in the target... smaller is better.

HTH

- Leigh
Or how about:
Precision = (group size) Repeatability.

Accuracy = (group placement) How close to the true value.

Resolution = How finely the scale can be read.

[Leigh]

What would an archer’s target look like if, say, three shots proved repeatable – but were not accurate or precise?
Precision does not have a proper analog in target shooting.

An inaccurate but repeatable group of arrows would have the first one somewhere on (or off) the target,
with the next one stuck in the back end of its predecessor. :eek:

- Leigh

[Leigh]

Or how about:
Precision = (group size) Repeatability.
Accuracy = (group placement) How close to the true value.
Resolution = How finely the scale can be read.
Yeah, that would work, but it's at variance with the terms commonly used in metrology.

- Leigh

[E. von Hoegh]

Yeah, that would work, but it's at variance with the terms commonly used in metrology.

- Leigh

I know, I was trying to come up with terminology understandable to those competent in English, but not necessarily technonerds. (winking smiley)

[Leigh]

I agree.

The essence of language is communication.

It doesn't matter what you say, if the listener doesn't understand the terminology, the message is lost.

The concepts of measurement that have teen discussed above are ancient, going back at least to the Babylonians.
It's just a question of how to express them in modern terms.

- Leigh

[rdenney]

Precision does not have a proper analog in target shooting.

What about the spacing of the rings on the target?

Rick "not asking for approval, and not expecting any" Denney

[Leigh]

What about the spacing of the rings on the target?
That would be accuracy in the printing process.

Precision is the fineness of the displayed measurement, the number of digits on a DVM display, for example.

A reading of x.xxxx is more precise than a reading of x.xx.

- Leigh

[SergeiR]

Put some distilled water into a pot and bring it to a good rolling boil. Your reading should be 100°C (212°F).
Nope. Depending on the altitude boiling point may be different from 100C.


Anyway - as long as under same conditions measuring device will give same results - not really important. Can just tape up scale to the desired point even if it reads 100 at 90 - who cares as long as its 90 every time ;)

[rdenney]

That would be accuracy.

Precision is the fineness of the displayed measurement, the number of digits on a DVM display, for example.

A reading of x.xxxx is more precise than a reading of x.xx.

- Leigh

Leigh, you can sure be both patronizing and disputatious. Must be part of the old-fart gig. But at least you didn't violate my expectations.

That's why I said the spacings of the rings, not their position. A target with three rings that is a foot wide provides less ability to measure precision than a target with ten rings that is the same foot in width. Each measures error, but one does so with more precision.

Rick "a licensed engineer in a number of states who can stamp ground surveys that live or die on the difference between accuracy and precision" Denney

[Vaughn]

...Rick "a licensed engineer in a number of states who can stamp ground surveys that live or die on the difference between accuracy and precision" Denney

In my forestry engineering classes (public land surveying -- back in the early 70's) the instructor mentioned that many of the corners set in Humboldt County back in the 1800's were actually "set" at the corner of the bars of Eureka (and with the future President Grant probably at the same bars -- I don't think he enjoyed being stationed so far west...and so far from San Fransisco, too).

[Leigh]

Leigh, you can sure be both patronizing and disputatious. Must be part of the old-fart gig. But at least you didn't violate my expectations.
Hi Rick,

Wow. I've been accused of a number of things in my life, but this is the first time for 'disputatious'. :p

I thought you were talking about the position of the rings on the target, not the number of rings.

I agree with you in the latter case re precision.

- Leigh

[Leigh]

Nope. Depending on the altitude boiling point may be different from 100C.
True statement.

- Leigh

[Heroique]

Hmm. I think we’re almost there. :D

Can we set aside “accuracy” for a moment for this fine-tuning question:

Does a “repeatable” event always presume that someone’s definition of “precision” is being met? It’s beginning to sound to me that these two parameters are not independent from each other; one must come with the other.

The example of one arrow splitting its predecessor is “repeatable,” Leigh has explained, without the repeatable event being “precise.” (“Precision does not have a proper analog for target shooting,” he says.) But isn’t there an implicit definition of precision at work here? Namely, hitting the back end of the preceding arrow, and not missing it?

A few posts back, Rick did mention that a thermometer w/o a scale has zero precision, but is highly repeatable. But how can one make a claim for repeatability if there’s no scale at all?

[Leigh]

A few posts back, Rick did mention that a thermometer w/o a scale has zero precision, but is highly repeatable. But how can one make a claim for repeatability if there’s no scale at all?
I agree with Rick on that point.

You can draw a line on the glass with a wax marker.
If the needle always falls directly under that line, the reading is repeatable even though you don't know the actual value.

All readings are limited by the precision of the instrument, so that applies equally to the issue of repeatability.

A good example of enhanced repeatability that does not affect the precision is mirrored scales on panel meters.

You read the instrument by looking past the needle to the reflection of your eye's pupil in the mirror. When the
the needle bisects the image of the pupillary disc, your eye is lined up directly over the needle and you can read
the meter scale more accurately than if you had not corrected for parallax.

This enhanced accuracy is reflected in the spec for the meter, with mirrored-scale meters being typically 1%
as compared with the 2% spec for non-mirrored meters.

- Leigh

[E. von Hoegh]

A non mirrored meter (thermometer) can be enhanced by making a mark over the needle, on the glass. This works only for that one needle position/value though.

[E. von Hoegh]

What about the spacing of the rings on the target?

Rick "not asking for approval, and not expecting any" Denney

That will affect the scoring, not the precision/shooter of the rifle itself.

[E. von Hoegh]

Nope. Depending on the altitude boiling point may be different from 100C.


Anyway - as long as under same conditions measuring device will give same results - not really important. Can just tape up scale to the desired point even if it reads 100 at 90 - who cares as long as its 90 every time ;)

Depending upon the altitude and barometric pressure.

[Drew Wiley]

Why an accurate thermometer is important : At 10,000 ft when water starts boiling, you
can put your finger in it and it will still be lukewarm. Your food will not cook. At sea level
if you do the same, you will have your finger for dinner. Even more important is the morning
if you like hot coffee. Maybe frivolous information to a lot of you, but after a long day on
the trail, and a cold evening arriving, I happen to like a hot meal. However, a Kodak Process thermometer is not necessary. I just wait for what is termed a "rolling boil".

[tgtaylor]

Maybe frivolous information to a lot of you, but after a long day on
the trail, and a cold evening arriving, I happen to like a hot meal. However, a Kodak Process thermometer is not necessary. I just wait for what is termed a "rolling boil".

A high altitudes a "rolling boil" (the boiling point) occurs at a lower temperature than at sea level. Any therometer can be calibrated to read accurately at any altitude/pressure by simply doing the math incorporating the barometric pressure and altitude. I'm sure that there's an app for it also.

Thomas

[ic-racer]

simply doing the math incorporating the barometric pressure and altitude.
Even easier if you known the pressure at the location of your thermometer (using a gauge). In that case you don't need to know the altitude.

[Drew Wiley]

Yeah, it's probably just a matter of time till someone shows up in the mtns with a barometric calibrated temp probe on their combination camera/cell phone/GPS. It sure is
annoying to have someone along with on the trail punching little buttons to check on their
stock portfolio or purchase something online. I thought the whole idea of getting outdoors
was to get away from that crap.

[Vaughn]

back in my wilderness ranger/trail building days I took the fire crew out for a week to get them in shape. One of them was a CB nut and wanted to bring one along. I nixed it. But then I was always getting in trouble for not calling in on my radio everyday...I always said I was down in a canyon and could not hit a repeater...:)

I was also in favor of a no-rescue policy in the wilderness, too, but never got very far in getting the policy instated. But at least I got our sign policy to state that we'd only sign trail junctions. If people want to know what creek they are at, they should know how to read a map! And since the budget was cut so badly after I left 21 years ago, most of the routed oak signs I installed have fallen off, so the wilderness is just about unsigned again!

[Drew Wiley]

Nowadays you've got those simplified sattelite GPS 911 units which will only signal emergency, but will do so with a selective degree of urgency. I actually wouldn't mind
owning one of those if I was traveling alone way off trail during old age. But last summer
a wilderness ranger in Sequoia was commenting on how many false alarms they were getting which tied up their time and energy, and potentially distracted from true emergencies. So they're thinking about whether or not to impose stiff fines for calling a
a search or helicopter party for something like mosquito mania or leg cramps, or for the
fact that the freeze dried dinner won't cook fast enough even though the water
is boiling.

[Heroique]

Most of the routed oak signs I installed have fallen off, so the wilderness is just about unsigned again!

(Warning: thread drift continues below...)

I like it when the wilderness reclaims the land.

Go Wilderness!

People who can’t read maps usually perceive disintegrating trail signs as an encroachment by the wilderness, not as a reclamation.

[Lungeh]

Why an accurate thermometer is important : At 10,000 ft when water starts boiling, you
can put your finger in it and it will still be lukewarm. Your food will not cook. At sea level
if you do the same, you will have your finger for dinner. Even more important is the morning
if you like hot coffee. Maybe frivolous information to a lot of you, but after a long day on
the trail, and a cold evening arriving, I happen to like a hot meal. However, a Kodak Process thermometer is not necessary. I just wait for what is termed a "rolling boil".

At 10,000ft ASL pure water boils at 194° (90°C). Hot enough to burn my finger... just not as quick. Most food will cook, cakes will even bake.

The terms "accuracy, precision and reliability" are widely accepted across (pretty much) all technical fields with only minor redefinitions for specialty jargon. If you share a lab/equipment there are further refinements such as "inter-observer reliability" and so on.

Nice discussion of metrology, verging on epistemology if you are perspicacious enough.

[Drew Wiley]

You obviously have not spent the hundreds of nites I have in the mtns, often waiting for
the food to cook. And I don't know what your standard of pure water is. Up there it's about as pure as it gets, almost direct snowmelt, plus about 50% mosquito larvae content.

[Vaughn]

People who can’t read maps usually perceive disintegrating trail signs as an encroachment by the wilderness, not as a reclamation.

I once got a letter from a wilderness user complaining about our signs -- said that we should someone out into the wilds from the city and have him/her tell us where to put the signs. I do not think I ever wrote back...bad ranger, bad ranger!

But between the lack of trail maintenance and some fires that have rolled through there, the Yolla Bollys are getting more and more wild again. I am taking my three boys there this summer and we are going to do a week's worth of trail mainentance volunteering. Just got a email from the wilderness person on the district -- I have to get "certified" to use a cross-cut saw! It would be funny if it weren't so stupid!

Vaughn

[E. von Hoegh]

You obviously have not spent the hundreds of nites I have in the mtns, often waiting for
the food to cook. And I don't know what your standard of pure water is. Up there it's about as pure as it gets, almost direct snowmelt, plus about 50% mosquito larvae content.

I hate underdone larvae.....

[BetterSense]

I have Taylor waterproof digital thermometers. I use them for photography and brewing, and they are cheap and work great. But really, I have found that I can sense water temperature well enough by just feeling it with my hand. That's all the precision I need for B&W.

[Bruce Douglas]

For boiling point, what you really need to know is what the barometric pressure is. Pressure affects the boiling point. Barometric pressure not only varies with altitude but also with the weather.

I checked the accuracy of the old Premier dial thermometer I use with two electronic thermometers and decided it was reading two degrees F high. I develop my film in Xtol at 68 degrees F. When I want solutions at 68 deg F I adjust their temperature so my dial thermometer indicates 70 deg. F.

The most important thing the thermometer does for you is to ensure that you are developing film under consistent conditions to yield consistent results.

[Heroique]

I think we need a good scientist around here to distinguish between “boiling point” and “normal boiling point.”

Otherwise, this thread’s going to get bloody, brutal and ugly – and finally locked.

[Leigh]

... to distinguish between “boiling point” and “normal boiling point.”
You actually expect anybody on this board to understand the meaning of "normal"?

You certainly are an optimist. :p

- Leigh

[ic-racer]

I think we need a good scientist around here to distinguish between “boiling point” and “normal boiling point.”

Otherwise, this thread’s going to get bloody, brutal and ugly – and finally locked.

Yes, at 101.325 kPa which you are measuring with your barometer.