Infrared Thermometer on Sale - Fiberglass RV


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Old 06-17-2007, 02:27 PM   #1
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Harbor Freight has an Infrared Thermometer with Laser Sighting on sale for $19.95, both on their website and at the local stores (at least it was at ours, bring website page in for price matching if needed the clerk said). After some informal testing, it appears to be reasonably accurate and consistent.

Use this for testing trailer hub, transmission coolers, refrigerators, and assorted pets.

* Readings in Fahrenheit or Celsius
* Temperature range: -27 to 482F (-33 to 250C)
* 40 hour battery life
* Exclusive ergonomic trigger control
* 6:1 spot size to distance ratio

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=93984 You can also view the product manual on that page. It claims an accuracy of 2%, or 4F, whichever is higher.

This photo when expanded is slightly smaller than life-size!
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Old 06-17-2007, 04:32 PM   #2
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Hot idea
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Old 06-17-2007, 05:09 PM   #3
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All IR thermometers work quite well close to 72 F air temperatrue. The farther away you get from standard room temperature the worse they are. It has to do with the physics of Infrared radiation and 4th order curves. As far I know there's only two manufacturers of IR thermometers that will work over a wide range of air temperatures. They sell under the brand names of Surface Patrol and RoadWatch. They are also a lot more expensive that $19.95.

So buyer beware, sometimes you don't get what you pay for.
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Old 06-17-2007, 05:57 PM   #4
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I only travel when its 72F so I'm good to go with this cheapo IR gadget!
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Old 06-18-2007, 11:39 AM   #5
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For those of us in Canada, Princess Auto carries similarly priced IR thermometers. The accuracy specs are printed in detail on the packaging, so you can judge how well it suits the purpose. They have two models: one looks generally like the Harbor Freight item, and has a wide field of view (wider than 6:1); the other is a much more directional "spot" design (12:1?). I just bought the spot version, but have not had a chance to try it out.
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Old 06-18-2007, 11:50 AM   #6
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Used mine on the coffee pot today. Just after brewing the side of the glass pot was 155F, about 20 minutes later 168F, and another half hour about 185F. The hot plate was 255F or so.
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Old 06-18-2007, 07:15 PM   #7
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If you go to the Harbor Freight site and search "thermometer", you will not only come up with the referenced $20 IRT, but there's another (without the laser) for $10. Don't know the relative technical differences.
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Old 06-18-2007, 09:39 PM   #8
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I'm currently and have been for several years 1/2 of the design team for RoadWatch brand of IR thermometers. RoadWatch is used by most state DOTs to tell when to put down salt, sand, etc. on cold roads. The biggest single obstical to over come is the way IR energy works along with the basic IR sensor. The raw sensor will work very well over a wide range of "object" temperatures, but not so well over a wide range of air temperatures. It has to do with something called the "black body curve". To make the unit (RoadWatch) work over a wide range of air temperatures a lot math is involved. Even more calculations involved in making each unit work the same, often call calibration. We've spent close to 15 years creating the math necessary to make the units work from -40F to 130F air temperatures.

My point is that there cannot be the calculations necessary in such a cheap unit. Relying on a $20 or even a $300 IR thermometer is like relying on a $1.00 pair of tires. The problem is that the farther away from room temperature (72) the more inaccurate they are and direction of inaccuacy is to read colder than the actual temperature.

They can be fun to play with, but please don't rely on them to tell you if you have a problem.
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Old 06-18-2007, 11:24 PM   #9
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I intend to use mine for the mission-critical task of checking trailer hub temperatures. I can either grab the hub with my hand and determine that its hotter than the day before, but maybe not as hot as the long day two days ago, or use this IR device and have a much, much better idea for $20. Or I could just ignore the hubs and hope the good results from the bearing check I did 10,000 miles ago is still good.

Sometimes you just got's to use the best tools you can afford and hope for a good outcome.
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Old 06-19-2007, 08:57 AM   #10
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Byron, Your comments on errors in reported temperatures from infrared thermometers are very interesting and your credentials to make such comments are impressive. Like Patrick, I walk around my rig and trailer feeling hubs and tires with my hands and often find myself jumping back and forth between hubs as I try and register the differences. Even if the inexpensive IR units have an accuracy that varies with air temperature, wouldn't they still be of some use when one is trying to simply identify relative differences in hub temperature, as Patrick and I say we do -- when the air temp is constant? The absolute temp, while it might be nice to know, is less important to me than the relative difference. (Guess I'd be in trouble through when both hubs are going at the same time.)

And Byron, put me at the front of the line when you are looking for volunteers to field test your units at high elevations in the mountains.

I'm always astonished at the backgrounds and levels of expertise represented on the forum-- and the willingness of so many to share that expertise.

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Old 06-19-2007, 09:15 AM   #11
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I'm currently and have been for several years 1/2 of the design team for RoadWatch brand of IR thermometers. RoadWatch is used by most state DOTs to tell when to put down salt, sand, etc. on cold roads. The biggest single obstical to over come is the way IR energy works along with the basic IR sensor. The raw sensor will work very well over a wide range of "object" temperatures, but not so well over a wide range of air temperatures. It has to do with something called the "black body curve". To make the unit (RoadWatch) work over a wide range of air temperatures a lot math is involved. Even more calculations involved in making each unit work the same, often call calibration. We've spent close to 15 years creating the math necessary to make the units work from -40F to 130F air temperatures.

Awesome credentials and comments. Thank you. I've wondered about these things as well.

My comments are more about trailer bearings and inspection. Personally, I've always checked my bearings by hand and if they're anything warmer than body temperature, I know I have a potential problem... Mostly, my hubs are cold after a multi-hour drive. Now, granted, the situation is probably different now that my trailer has brakes, but after a 1 hour highway drive this weekend, I came home to find my hubs cold to the touch... So, in my non-expert opinion, you don't really need a thermometer to gauge the condition of your bearings...

As an amateur who does his own automotive work, I can tell you I don't repack the bearings on any of my vehicles every year, nor every two years, nor even every 10,000km... Trailer bearings aren't any different from automotive bearings (albeit smaller than your average truck bearing, but about the same size as the bearings on your jeep or honda)... Boat trailer bearings are slightly more prone to having issues given they regularly get dunked in water... I will also admit to checking my bearings after an offroading trip where I've driven through a river or stream for any appreciable distance...

So, if you're dunking your hubs in rivers/lakes for more than a few seconds, then by all means, check/repack them. Otherwise, just feel with your hands.
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Old 08-03-2007, 08:13 AM   #12
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These are on sale again thru the 8th- this time for $17.99!
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Old 08-03-2007, 04:28 PM   #13
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I ordered the less expensive, smaller one without the laser -- It seems to be reasonably accurate (compared to touch, not tenths) but I sometimes have to trigger it several times to get good readings.
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Old 12-10-2007, 10:19 AM   #14
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On the latest TV program "Cool Tools" (Dec 07) they showcased an IR thermometer and explained that it measures the IR wave lengths and converts it to the temp reading.
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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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Quote:
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.

Quote:
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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