Paterson Certified Thermometer reability

[radialMelt]

I’m not sure there is a whole lot you can do unless you spend relatively big money on a calibrated/certified thermometer. I did that years ago because I needed (wanted is probably more accurate ) one for non-photographic purposes, and I use that as a reference for the cheaper thermometers I actually use for photo stuff (several Patersons). They are all +/- a few 10ths of a degree C and that is plenty good for black and white photography. Color processing is more sensitive but I don’t know what level of accuracy is needed.

Kodak states temps should, ideally, be accurate to .15C. Of course this is super difficult to achieve in a home setting. However, I would absolutely love to have a thermometer I can trust.

 

[snusmumriken]

Are there any current offerings in the way of thermometers that can be trusted fully?

Apart from the technical points in post #38 above, one thing I learned from a career in biology was that temperature is a momentary measure reflecting the dynamic relationship between the thermometer and its environment, unless that environment is extraordinarily stable. Two theoretically identical thermometers (if they can be found) placed in the same bath, may never read exactly the same. Having said that, any one glass thermometer will do the same thing in the same circumstances, every time. How precisely do you want to measure temperature, and how accurate must that be? Certification presumably relates to accuracy. But surely the important aspect of the Kodak recommendation is precision (i.e. cut out variation for consistent results), rather than accuracy relative to the freezing point of krypton or something.

 

[JerseyDoug]

Correct me if I'm wrong but if they are supposed to be accurate to +/- .12C, then the max difference between the two thermometers should be .24C, no?

Apologies. You're right. I deleted the offending paragraph.

 

[BobUK]

I have been thinking about Kodak and Paterson.
Kodak being American would most likely use the Fahrenheit scale, whilst Paterson being European, I think, would use the Celsius scale.

With the help of an online converter I found that each step up of 1 C would be 1.8 F on the Fahrenheit thermometer scales.

So would that make the Fahrenheit scale a more accurate scale to use?

Also a given percentage accuracy e.g. 1% would be completely different in practice between each scale.

Can some one tell me if my reasoning is correct please?

 

[Chan Tran]

I have been thinking about Kodak and Paterson.
Kodak being American would most likely use the Fahrenheit scale, whilst Paterson being European, I think, would use the Celsius scale.

With the help of an online converter I found that each step up of 1 C would be 1.8 F on the Fahrenheit thermometer scales.

So would that make the Fahrenheit scale a more accurate scale to use?

Also a given percentage accuracy e.g. 1% would be completely different in practice between each scale.

Can some one tell me if my reasoning is correct please?

The scale doesn't matter.

 

[MattKing]

I have been thinking about Kodak and Paterson.
Kodak being American would most likely use the Fahrenheit scale, whilst Paterson being European, I think, would use the Celsius scale.

With the help of an online converter I found that each step up of 1 C would be 1.8 F on the Fahrenheit thermometer scales.

So would that make the Fahrenheit scale a more accurate scale to use?

Also a given percentage accuracy e.g. 1% would be completely different in practice between each scale.

Can some one tell me if my reasoning is correct please?

On a thermometer like this, the Celsius markings are farther apart, and there is more room to add markings for partial degrees Celsius.
So there is no difference.

 

[_T_]

Standard practice for calibrating a liquid thermometer is to measure the reported temperature in an ice bath and a beaker of boiling water.

So I highly doubt that a few minutes of even scalding hot water would make a difference. And if it did, recalibrate it by measuring some ice water and a pot of boiling water and write down how far off from predicted the results are.

You would want to calculate the predicted temperature for boiling water at your elevation for this.

Also you would know if the hot wash water had changed the calibration because you would see that the column of liquid had become discontinuous, so you could just look at it. Pretty sure someone mentioned that before. But it's a good idea to calibrate even a brand new thermometer because they can have some error.

 

[cmacd123]

Standard practice for calibrating a liquid thermometer is to measure the reported temperature in an ice bath and a beaker of boiling water.

although many thermometers are not actually rated to withstand 100C.

Kodak did at one time sell special reference thermometers, for a couple of Hundred bucks. the idea was a photo lab would have one and check the other ones in the lab against it. the ones that were closest to matching would be assigned to the critical stages (like reversal first developer) and the ones which are off by a half degree C would work for things like Fixer.

for a whole lot of Money you can even get a real Lab brand suplier thermometer with a certificate that says it was checked against the National Bureau of Standards. a manufacturing plant could perhaps justify having one from their own calibration lab.

the NRC here in Ottawa even can provide calibration for temperature for a few thousand dollar per point... https://nrc.canada.ca/en/certificat...ces/thermometry-humidity-calibration-services

 

[Chan Tran]

You can always use the ice point and boiling point to check the thermometer for example the Kodak Process Thermometer Type 3 only reads from 50 to 140F so it can't read either the ice point or boiling point.

 

[MattKing]

You can always use the ice point and boiling point to check the thermometer for example the Kodak Process Thermometer Type 3 only reads from 50 to 140F so it can't read either the ice point or boiling point.

I expect you meant to say: "You can't always use the ice point and boiling point to check the thermometer. For example, the Kodak Process Thermometer Type 3 only reads from 50 to 140F so it can't read either the ice point or boiling point.

 

[Chan Tran]

I expect you meant to say: "You can't always use the ice point and boiling point to check the thermometer. For example, the Kodak Process Thermometer Type 3 only reads from 50 to 140F so it can't read either the ice point or boiling point.

yes you're right. I meant to say you can't. If you subject such a thermometer to 212F I am quite sure it would be damaged.

 

[MattKing]

yes you're right. I meant to say you can't. If you subject such a thermometer to 212F I am quite sure it would be damaged.

And you might have mercury all over the place!

 

[mshchem]

With the Kodak thermometers you can use an ice bath to pull the liquid down into the bulb if it becomes separated.

 

[BobUK]

The scale doesn't matter.

On a thermometer like this, the Celsius markings are farther apart, and there is more room to add markings for partial degrees Celsius.
So there is no difference.

Perhaps I did not explain myself very well.


Assuming a rise of 1 degree C is the same as a rise of 1.8 degrees F.

To find 1% of 1 degree C , divide by 100. Likewise, to find 1% of 1.8 degrees F , divide by 100.

This equals 0.01 of a degree C and 0.018 of a degree F respectively.

Both figures are the same temperature shift.

But possibly a non mathematical person such as myself, looking at these figures or ratios, with reference to a percentage accuracy figure would think the Centigrade figure was more accurate.

Sorry, the thought is in my head, but trying to get it over is one over those you see it or you don't.

Hopefully some one else is on the same wavelength as me.

Thanks for replying.

 

[Chan Tran]

Perhaps I did not explain myself very well.


Assuming a rise of 1 degree C is the same as a rise of 1.8 degrees F.

To find 1% of 1 degree C , divide by 100. Likewise, to find 1% of 1.8 degrees F , divide by 100.

This equals 0.01 of a degree C and 0.018 of a degree F respectively.

Both figures are the same temperature shift.

But possibly a non mathematical person such as myself, looking at these figures or ratios, with reference to a percentage accuracy figure would think the Centigrade figure was more accurate.

Sorry, the thought is in my head, but trying to get it over is one over those you see it or you don't.

Hopefully some one else is on the same wavelength as me.

Thanks for replying.

2 different units so for example 1 cm is more resolution than 1 inch. But if you divide the 1 inch into 10th then the inch scale has more resolution. Then again you divide the cm scale into 10th or mm then once again the cm scale has more resolution. So the resolutions don't match but they can be made more or less and it doesn't depend on the unit used. Very often this resolution stuff is irrelevant because the accuracy of most instrument is less than its resolution. For example a lot of digital thermometer can display in 10th or a degree but most rarely has accuracy of better than 1 degree.

 

[RalphLambrecht]

Hot tap water is usually about 50°C/120°F. If your thermometer's range is less than that, you could risk breaking the thermometer by leaving it in too-hot water for a long time (the internal pressure can crack the tube or top of the glass column). However, if your thermometer is intact and the fluid column is not separated, no damage has been done and the thermometer is likely as accurate as it always was.

Do check for cracks and fluid separation. The latter problem can be remedied by heating the thermometer slowly till the fluid reaches the very top of the column and rejoins, then remove it quickly from the heat source and let it cool slowly.

If you're still in doubt, find a reliable thermometer to check against.

Doremus

Would it make sense to measure the outside temperature and compare the result to the actual report of the local weather station?

 

[Chan Tran]

Would it make sense to measure the outside temperature and compare the result to the actual report of the local weather station?

Not at all! If you do that you might as well just feel like how hot or cold it is.

 

[cmacd123]

Would it make sense to measure the outside temperature and compare the result to the actual report of the local weather station?

may or may not be useful depending on how close you live to your local airport. and what the Terain is like between "here" and "There"