Infrared Thermometer on Sale - Page 2 - Fiberglass RV


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Old 12-10-2007, 10:47 AM   #15
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We bought a more expensive one from Harbor Freight. Cen-Tech item 91778. As soon as we got home I checked room temperature. It is 7 to 8 degrees off. Tried it on my freezer and my freezer was well below 0. Now I need to find a good thermometer to put in the freezer to see what it really is because the IR has to be off there too. Oh heck, it is 0 outside now, guess I could stick my head outside and see what the faulty Cen-Tech says.

Oh well, it should still be better than nothing to check the hubs. I did want it for checking the heat put off by the George Foreman grills. Different grills have different information for how long to leave an item on. So I hoped to check the difference between the G5 and the cheapie, etc.

If people want this for stocking stuffers (ours is a bit big for that) be aware that it might not be so accurate.

Nancy
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Old 12-10-2007, 11:01 AM   #16
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We bought a more expensive one from Harbor Freight. Cen-Tech item 91778. As soon as we got home I checked room temperature. It is 7 to 8 degrees off. Tried it on my freezer and my freezer was well below 0. Now I need to find a good thermometer to put in the freezer to see what it really is because the IR has to be off there too. Oh heck, it is 0 outside now, guess I could stick my head outside and see what the faulty Cen-Tech says.

Oh well, it should still be better than nothing to check the hubs. I did want it for checking the heat put off by the George Foreman grills. Different grills have different information for how long to leave an item on. So I hoped to check the difference between the G5 and the cheapie, etc.

If people want this for stocking stuffers (ours is a bit big for that) be aware that it might not be so accurate.

Nancy

Two things determine accuracy of IR thermometers. One is the emissivity which the IR calibration device (what the factory used to calibrate it, if anything from Harbor Freight is calibrated), vs the emissivity of the item you're attempting the measure. Two, the air temperature. These devices are all set to work at room temperature. When you get away from room temperature (72F) the temperature readings somewhat follow the "black body" curve. In other words they're not correct, depending on air temperature not even close.

I probably answer this same type of thing 50 or more times a year. Customers want to know why our $600.00 product doesn't measure the right temperature. When I ask what they're using to compare it with, it's often something like the unit you purchased.

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Old 12-10-2007, 11:44 AM   #17
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The IRs don't measure air temperature (I think), so that might be part of the difference. I assumed at this price they're not real accurate but have used mine to establish a "base" temp for the hub and tires, both on the shady side (110F or so) and the sunny side (130F) of the trailer at rest stops, and hope that the guage will register accurately a big change that might indicate a problem.
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Old 12-10-2007, 12:58 PM   #18
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I would not be so quick to judge the IR thermometers as inaccurate. In assessing any instrument by comparing its reading with another one, the accuracy of the reference instrument has to be considered... and any thermometer sold for home use is approximate. The other problem is, as has been explained, that the IR instrument measures the temperature of a surface - subject to all sorts of conditions and effects. Sitting in a room in the winter, even if I knew the air temperature around me with perfect accuracy (and I don't), I wouldn't know what temperature to expect of various surfaces; an outside wall would certainly be much cooler than the room air.

Even if these things are way off (several degrees at room temperature), as a way to check if hub temperatures are reasonably or scorching hot they seem like a useful tool, as Patrick M. has suggested.

I have one; it certainly shows small temperature differences between objects which seem slightly different in temperature to the touch, and provided some interesting numbers when I did some brake testing. I have not used it for hub temperatures because (until I lost one on B. C. Highway 99) both of the Boler's hubs are hidden by full wheel covers that are a pain to remove and replace.

The application which Bryon has worked with - assessing road surface temperature - seems much more demanding of accuracy and challenging in conditions than checking hub or brake temperatures. I guess it's a matter of choosing the right tool for each job and understanding its limitations.
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Old 12-10-2007, 01:34 PM   #19
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I would not be so quick to judge the IR thermometers as inaccurate. In assessing any instrument by comparing its reading with another one, the accuracy of the reference instrument has to be considered... and any thermometer sold for home use is approximate. The other problem is, as has been explained, that the IR instrument measures the temperature of a surface - subject to all sorts of conditions and effects. Sitting in a room in the winter, even if I knew the air temperature around me with perfect accuracy (and I don't), I wouldn't know what temperature to expect of various surfaces; an outside wall would certainly be much cooler than the room air.
I'm not sure you understood what I said. Most IR thermometers are calibrated at room temps (72F). Air temperature variations away from the calibration point will effect the displayed IR temperature. It's all in the physics of the IR sensor (thermopile).

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Even if these things are way off (several degrees at room temperature), as a way to check if hub temperatures are reasonably or scorching hot they seem like a useful tool, as Patrick M. has suggested.

I have one; it certainly shows small temperature differences between objects which seem slightly different in temperature to the touch, and provided some interesting numbers when I did some brake testing. I have not used it for hub temperatures because (until I lost one on B. C. Highway 99) both of the Boler's hubs are hidden by full wheel covers that are a pain to remove and replace.
Yes you can get a reference difference when looking at large differences between something like hubs. But it won't work very well to say that day my hubs read 110 today and expect to measure 110 another day. If you measure both hubs at on the same day you might, emphasis on might, be able to tell if there's something wrong. If you take your hand held from a warm room to great outdoors when the temperature is considerably different the reading probably will change for up to 1/2 hour until the internal workings of the thermometer all get to the same temperature.

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The application which Bryon has worked with - assessing road surface temperature - seems much more demanding of accuracy and challenging in conditions than checking hub or brake temperatures. I guess it's a matter of choosing the right tool for each job and understanding its limitations.
The biggest problem working any IR temperature measurement is not the surface temperature, it's the air temperature. If I could keep the IR sensor at the same temperature all the time it wouldn't be a problem. FLIR that makes the IR video cameras super cools the IR sensor, I can't do that, neither can Harbor Freight's supplier. So we spend many many hours creating mathematical ways to compensate for different air temperatures and adjusting the math for differences from unit to unit.


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Old 12-10-2007, 05:58 PM   #20
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I'm not sure you understood what I said. Most IR thermometers are calibrated at room temps (72F). Air temperature variations away from the calibration point will effect the displayed IR temperature. It's all in the physics of the IR sensor (thermopile).
Yep, no problem understanding... I just meant that when someone says "my IR thermometer is wrong" they are likely aiming at a surface and comparing to an air temperature reference. Even if the air is at 72F, and the IR instrument is perfect and perfectly calibrated, the surface may legitimately be a different temperature, so the comparison leads to invalid conclusions.

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Yes you can get a reference difference when looking at large differences between something like hubs. But it won't work very well to say that day my hubs read 110 today and expect to measure 110 another day. If you measure both hubs at on the same day you might, emphasis on might, be able to tell if there's something wrong. If you take your hand held from a warm room to great outdoors when the temperature is considerably different the reading probably will change for up to 1/2 hour until the internal workings of the thermometer all get to the same temperature.
Good point... but if we're talking about "a little warm to the touch" versus "so hot it would burn my hand because the bearings are disintegrating" then the instrument is useful. If real mechanical problems do not produce a big enough temperature difference then it isn't useful; however, even an accurate contact thermometer would be limited in that case.

Also, if one bearing is dying or one tire is overheating due to excessive load or inadequate inflation (and those do seem to be the issues that people are concerned about), then a side-to-side comparison (as Byron mentioned) may be enough (yes, sunshine on the tires will have an effect). Since the instrument is in the same ambient conditions on each side, the calibration error would be similar and the comparison (if not the absolute value) would be meaningful.
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Old 12-10-2007, 06:01 PM   #21
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The application which Bryon has worked with - assessing road surface temperature - seems much more demanding of accuracy and challenging in conditions than checking hub or brake temperatures.
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The biggest problem working any IR temperature measurement is not the surface temperature...
I meant that measurement of the road surface temperature seems likely to be critical (a couple of degrees would make a big difference) compared to hub, brake, or tire temperatures; and that a road surface is nasty (variable in emissivity, and going by at speed, for instance) compared to mechanical components (such as stationary hubs, brakes, or tires). I understand that ambient air temperature is an issue in either case, but even then we tend to camp in ambient temperatures somewhat closer to the calibration point (e.g. 72F) than the road icing detection systems work in.
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Old 12-10-2007, 06:11 PM   #22
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I meant that measurement of the road surface temperature seems likely to be critical (a couple of degrees would make a big difference) compared to hub, brake, or tire temperatures; and that a road surface is nasty (variable in emissivity, and going by at speed, for instance) compared to mechanical components (such as stationary hubs, brakes, or tires). I understand that ambient air temperature is an issue in either case, but even then we tend to camp in ambient temperatures somewhat closer to the calibration point (e.g. 72F) than the road icing detection systems work in.
Just don't believe the numbers you see on the indicator.
Interesting assumption about camping at 72F or for that matter traveling only at that temperature.

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Old 12-11-2007, 12:09 AM   #23
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<chuckle>

So, we bought a travel trailer. No problem. How technical and complicated can owning a travel trailer be?

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Old 12-11-2007, 12:24 AM   #24
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<chuckle>

So, we bought a travel trailer. No problem. How technical and complicated can owning a travel trailer be?

Doesn't that depend on how many toys we have to have to go with it? <grinz>
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Old 12-11-2007, 06:34 AM   #25
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<chuckle>

So, we bought a travel trailer. No problem. How technical and complicated can owning a travel trailer be?

As technical and complicated as you want it to be. For some the gadgets and toys are part of the fun. Lucky for all of us, one size doesn't fit all.

As a geek by nature and training, I think gadgets are cool. My rule is: As long as the failure of a gadget doesn't curtail my camping...

A sometimes poster (Charles Watts) once posted a cautionary tale about having too much information. His story about having a remote thermometer in the trailer reefer and his angst over one or two degree drifts in it's internal temp serve as a warning to keep things grounded.

But I can understand back-to-basics campers. Been there done that, so over it. It's just not my style any more.

When my buddy first bought his Casita (long before me), I used to stare and poke at it in his side yard. I was so fascinated by all it's "systems" in a small compact package. (The ONLY thing I find fascinating about babies!)


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Old 12-11-2007, 07:21 PM   #26
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Gee, almost sorry I brought this thread back to life!

After playing with our new unit (aimed at objects close range) I have noticed that our IR is consistently 8-10 degrees cooler than the regular thermometers on/near the same object.

This should make me feel much cooler in the summer, but I don't need to know the book on my bookshelf (next to my room therm) says it is 52 degrees rather than my 60 degree bedroom. And I like the 9 degree daily high outside (in my protected north alcove) better than the 0 degrees with the IR.

Sure wish we had left the trailer in Tulsa for a January trip to Texas. Now we will have to do the air thing and stay in motels.

Nancy
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Old 12-12-2007, 10:36 AM   #27
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Not to worry Nancy, your other thermometer is not correct either, just like your watch does not have the exact time and your ruler does not have the exact measurement. The bureau of standards is the only people that have the exact measurements and everything else is just close. The scientific devices are closer and what we non-scientific people purchase are devices that are not as close but close enough for our daily life and that is good enough.

If you were a Scientist or the Military where you may require a precision time clock worth millions of $$ and measurements must be exact then close enough is not good enough.

The fact that your IR Thermometer is off a little will be good enough for you to spot cool spots around your doors and windows so you can take corrective action to plug those leeks and save some heating $$ in the winter and by doing so in the colder months it will save you $$ come summer during air condition time.

Your clock being several seconds or billionths of a second off will not matter because you will still get to your appointments on time, that is unless you are retired in which case It just doesnt matter.

When you take your IR thermometer camping and you read the hub temp you will most certainly know when something is wrong because it will not be just a few degrees off because a hub going bad will increasingly get hotter until it is really really hot and you can track it by taking the temp every time you stop for a break.

So relax and use your IR Thermometer as it was designed for and spot those leaks in your house and trouble spots on your vehicles and enjoy a trouble free life and well let the scientist worry about the small inaccuracies in our affordable daily measurement devices.
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Old 12-12-2007, 10:44 AM   #28
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I guess this all depends on what you call "small inaccuracies". A degree or two? how about 30 to 50 degress off or more?
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