Digital Thermometer Talk

[szpond]

Hey all,

For my Six Sigma & Statistical Process Improvement course at Uni I'll be conducting a study based on the performance of two brands of digital thermometers relative to each other.

I am interested in this topic because I purchased a Zilla digital thermometer for about $6-$7 on clearance awhile ago. Soon thereafter, I purchased an ExoTerra digital thermometer for between $15 and $20. Now, the Exoterra has more features, but I wanted to see if price really did determine performance in these cases. Do they show the same temperatures under the same conditions?

I'll be conducting an experiment by using an A vs. B model of paired hypothesis testing to rule out variability among trials. I'll be using different bulbs, different domes, and different distances away from the bulbs. I figure I'll test between room temperature to 110 degrees F to see if they hold true to each other.

The reason I emphasize that i'll be testing them relative to each other is that there really is no way for me to know which is right or if either of them are showing the true temperature at that point in time in those conditions.

If this interests anybody, I will post my findings in a few weeks.

Does anyone have any input on this subject? Have you seen a difference in the digital thermometers you use? This may be pushing it, but does anyone know how exactly these thermometers are calibrated or some general ideas on how they may work? I have a couple theories.

Thanks all.

 

[kdc5019]

This is a very interesting subject.

There are a bunch of digital thermometers out their and it teases the curiosity of many on which thermometer to buy. I have seen a huge different in different models of thermometers. Some times +- 5 Degrees.

This will prove to be great research.

Im trying to think of something that you could use as a control and the only thing i can think of that has proven to be reliable in many studies is an IR Thermometer

http://www.amazon.com/BAFX-Products...4&sr=8-2&keywords=infrared+thermometer+amazon

And by using two different domes and two different lights, your introducing variability.. why not use the same baseline and use the same dome and bulb at varying heights and temps?

 

[szpond]

This is a very interesting subject.

There are a bunch of digital thermometers out their and it teases the curiosity of many on which thermometer to buy. I have seen a huge different in different models of thermometers. Some times +- 5 Degrees.

This will prove to be great research.

Im trying to think of something that you could use as a control and the only thing i can think of that has proven to be reliable in many studies is an IR Thermometer

http://www.amazon.com/BAFX-Products...4&sr=8-2&keywords=infrared+thermometer+amazon

And by using two different domes and two different lights, your introducing variability.. why not use the same baseline and use the same dome and bulb at varying heights and temps?

Thanks so much for the link there, I'm going to read up on this product. I can't wait to see what comes out of this study.

I want to try different combinations of bulbs, distances, and domes to see what type of readings I can get. I have a few domes and many incandescent bulbs to measure the radiant heat at a certain distance away.

Though by pairing each experiment, I am reducing the amount of unexplained variation between pairs. But within pairs, there is a pair-wise dependence...whereas, from pair to pair, I can assume independence. I am talking in circles. Anyway, I wanted to use only one dome but my professor suggested I create many different environments utilizing all of the products I have at hand.

So, as an example, I'll be doing something like this:
In ideal conditions (no significant airflow, no objects nearby that give off heat, maintain a fairly steady temperature) - use the first thermometer and measure room temperature. Then turn on the light at a certain distance away for a certain amount of time. Record that hotter temperature and find the difference between hot temp - room temp. Then, move on to do the same thing for the second thermometer, in the SAME conditions (long after the light is turned off and the room temperature can be assumed "back to normal" as it was before), determine the difference. I will be testing those differences against each other for each situation/environment.

Though, that is my professor's want. What I originally wanted to do was to ignore the room temperature altogether and just test the temperatures that each thermometer shows under the same conditions. Though, he has the worry that they will vary together (in his words, one could be a few degrees off each time, pointing to calibration error) and thus give me the conclusion that my hypothesis is false. By doing it his way, it will show me more on how they behave.

Rambling over! Any suggestions? So far I have thought of using a material like styrofoam to poke the digital thermometer probe through to keep it in place while it is being heated, for I've read that the styrofoam has a high melting temp and won't bounce much heat back. I know that I really cannot use metal to hold the probes in this case. I also thought of using just a wooden dowel on two props and tying the thermometer probes to it each time, but I worry that this method wouldn't ensure the probe stays straight-up towards the light.

 

[MelissaB]

Great experiment! I can't wait to hear about your results.

 

[Djturna4thakidz]

I am into this too! I need to buy a couple new thrms

 

[kdc5019]

two other things off the top of my head. Are your temperature probes the same color? or are they different? is one black and one white, do they ahve the same surface area to absorb head for a reading? Also time is variable, how long are you holding the probe at a specific distance to allow it to settle?

Just different things to consider in your experiment.

 

[szpond]

two other things off the top of my head. Are your temperature probes the same color? or are they different? is one black and one white, do they ahve the same surface area to absorb head for a reading? Also time is variable, how long are you holding the probe at a specific distance to allow it to settle?

Just different things to consider in your experiment.

Thank you for your input!! It is highly valued. They are both black. Seemingly the same type of plastic coating. Their function shouldn't differ, so I figure their calibration and the way they work doesn't differ either - but this is something I may find out!
As far as the amount of time goes, I'd love to hear some suggestions. I was going to do 5 minutes to let the heat reach its constant. I could do longer as well to ensure the bulb is not still warming up. What do you think?

 

[Psychobunny]

Unless you have a standard by which to compare, a themometer that has a certificate of calabration, how do you know either of them are correct?

What would be the point is compairing 2 thermometers of unknown accuracy?

 

[szpond]

Unless you have a standard by which to compare, a themometer that has a certificate of calabration, how do you know either of them are correct?

What would be the point is compairing 2 thermometers of unknown accuracy?

Noting my first post, there is really no way for me to know the true temperature at the place in time at any moment. Much like how, if you have two technicians measuring the same thing, who is to say that either of them are right?

This is why I am comparing them to each other. My original hypothesis is that they perform the same way (as intended - for they have the same function). Though, this study will tell me ONLY if they do or do not perform the same way. I will not have causation at the end of this.

Empirical study can only identify differences, not prove identity. Once a statistically significant result is observed, then the practical significance of the difference can be assessed. I am only doing part 1.

Ideally, I'd like to know if the cheap clearance digital thermometer is "just as good" as the more expensive digital thermometer. Meaning, if they perform the same way. I can't tell you by the end of this if either of them are correct. That's not what I'm testing for.

 

[kdc5019]

Thank you for your input!! It is highly valued. They are both black. Seemingly the same type of plastic coating. Their function shouldn't differ, so I figure their calibration and the way they work doesn't differ either - but this is something I may find out!
As far as the amount of time goes, I'd love to hear some suggestions. I was going to do 5 minutes to let the heat reach its constant. I could do longer as well to ensure the bulb is not still warming up. What do you think?

IMHO 5 minutes is too short, ive done tests with halogen bulbs at varying distances at it took a solid 10 minutes to reach an equilibrium point.

Unless you have a standard by which to compare, a themometer that has a certificate of calabration, how do you know either of them are correct?

Your right you cant determine that, its comparing the two. It was suggested that he gets a thermometer that is certified and has a temperature tolerance as a baseline

What would be the point is compairing 2 thermometers of unknown accuracy?

Im pretty sure that you can find on their respective websites, what the temperature tolerances are.

 

[szpond]

IMHO 5 minutes is too short, ive done tests with halogen bulbs at varying distances at it took a solid 10 minutes to reach an equilibrium point.




Im pretty sure that you can find on their respective websites, what the temperature tolerances are.

The longer the better to reach that point, so I will extend it out. Thank you.
I have been trying to find more information on these models, but it appears to be rather scarce. The Zilla thermometer was clearanced, so I worry I won't be able to find another one in stores to check out the packaging. I want to attempt to contact their manufacturers to see if I can get any answers as well, but I am not sure what they'd be able to tell me.

 

[mowryrd]

As for your question about how a digital thermometer works if it's anything like a temp sensor in a car they simple run an electrical current through a metal that changes it's resistance with temp. The device converts the resistance into a temp reading.

 

[Psychobunny]

Noting my first post, there is really no way for me to know the true temperature at the place in time at any moment. Much like how, if you have two technicians measuring the same thing, who is to say that either of them are right?

This is why I am comparing them to each other. My original hypothesis is that they perform the same way (as intended - for they have the same function). Though, this study will tell me ONLY if they do or do not perform the same way. I will not have causation at the end of this.

Empirical study can only identify differences, not prove identity. Once a statistically significant result is observed, then the practical significance of the difference can be assessed. I am only doing part 1.

Ideally, I'd like to know if the cheap clearance digital thermometer is "just as good" as the more expensive digital thermometer. Meaning, if they perform the same way. I can't tell you by the end of this if either of them are correct. That's not what I'm testing for.

Oh, I understand what your doing now, sorry

 

[szpond]

As for your question about how a digital thermometer works if it's anything like a temp sensor in a car they simple run an electrical current through a metal that changes it's resistance with temp. The device converts the resistance into a temp reading.

Thanks so much for your comment! I was FINALLY able to get ahold of one of the manufacturer customer assistants that was able to provide me with some answers about how one of them works! Tomorrow, I am going to try the second company...wish me luck! Hopefully they turn out to be the same.

 

[szpond]

Oh, I understand what your doing now, sorry

I appreciate your comments, truly! Walking myself through a detailed answer is the best way to go to get me to better understand the subject, so I thank you for it! Anyway, I'll be writing up my methodology properly tomorrow. Tomorrow I'll be thinking more about how I'm really going to start this...

One main concern I have with my standard method is how I can get the sensor to sit upright facing the radiant heat source for an accurate reading for the full amount of time it must sit. I have been given a suggestion - a plate of syrofoam (large pocket, I would probably describe it) on a wooden rod spanned between two bases to elevate everything from the floor. Mainly I am trying to avoid metal 100%, but in all honesty I am not sure how to approach this,

are there any readers that have input?