They are supposed to give instant temperature readings of the surface
they are pointed at. But when I point it at the shiny copper pipe out of
my water heater, it reads just a degree or two above the cold water
input pipe (also shiny copper), even though the output pipe is so hot I
can barely touch it.
Are you using it within the specs? Different IR thermometers have
different fields of vision. If you're trying to take a reading from
too far away it might be picking up too much of the background. The
curved surface and reflectiveness of the material might have something
to do with it as well.
Even before my original post, I had been holding the thermometer within
one-half inch of the pipe, just to eliminate background readings from
being averaged in.
Here's how the plumbing is: the output of the heater is a threaded
nipple (can't tell if it's copper or steel). Screwed into the nipple is
a 2" long copper coupling. The output of the coupling is soldered to the
copper pipe that supplies the house. (Same arrangement on the supply side.)
At the nipple, I'll measure about 98F. At the middle of the coupling,
about 78F. Just above the coupling, about 73F. Still seems far to low,
considering how it feels to my hand.
At the laundry sink nearest the heater (about six feet), water measures
50F out the cold faucet, and 110F out of the hot faucet. Ambient is
I figured out why I there was such a small difference between the hot
and cold pipes: No hot water was being drawn. So the water in the supply
pipe was being heated, by conduction, from the water in the tank. When I
felt the supply pipe at least three feet ahead of the heater, it
definitely felt much colder. But the IR thermometer still read about
68F, a much smaller difference that I would expect based on the touch test.
I dare not "rough up" the pipe, because I worked too hard to polish it.
But I darkened a section with a black Magic Marker; that section read
about 3 degrees higher than 1/4 inch away directly off copper.
You really need to know what the focus angle is to have any clue at all
as well as what the instrument is designed for regarding surface
emissivities. Some of the less expensive are pretty basic and quite
flawed for anything but large flat surfaces (again, based on our
evaluation of competitors' products when designing one as noted previously).
Also, as I presume this is 1/2 or 3/4" pipe you may well be seeing
geometry effects from the curvature as well; there's almost certainly no
firmware compensation for that effect.
As somebody else noted, if knew which particular instrument, just
_might_ have significantly more specific information on how it works
internally. ( :) )
Below our target market so no direct help, sorry.
Did look at the users' guide for the device however...
Note particularly the following note 3 --
Also note this isn't claimed to be a very accurate device and it does
use a fixed emissivity as I suspected. That makes a big difference.
I'd also suspect you're having a difficult time in ensuring that the
spot of sensitivity is actually only on the pipe and that the curvature
is an issue as well since as you move the device closer to the pipe
probably you're occluding your view of the laser and the parallax
problem of where it's aiming as opposed to the "sweet spot" gets larger
as you get nearer to a small object.
The actual accuracy claimed is only the larger of 3% or reading or 5F
for room temperature ambient anyway in the calibration--that's not very
good and when taken to random object it's almost nothing.
To make one that worked well under a wide range of conditions was a real
trick when we were designing one; it wasn't at all hard to find ways to
fool almost all we bought/tested as benchmarks nor was it easy to
eliminate such problems from our product. In some areas we did quite a
bit better, others were hard enough that "not so much"...
My overall conclusion would be likely it's just as good as the
particular instrument will/can do; you're expecting to much of an
inexpensive tool for the conditions.
The manual states the emissivity is fixed 0.95. Ignoring the definition
of emissivity, does this mean that the accuracy figures in the
specifications apply only to surfaces with 0.95 emissivity?
My intended uses are very simple and do not require accuracy:
1. To locate insulation gaps in the envelope of my house (by scanning
the walls and ceiling and areas around the electrical outlets)and
looking for temperature changes.
2. To locate leaks in the hvac ducts in the attic. The ducts are above
the insulation in the attic's floor and are made of insulated fiberboard
(shiny, silvery exterior, fiberglass insulation on the inside). I'm
particularly concerned with losses at the junctions.
So this inexpensive thermometer seems suited for these uses.
Only the manufacturer knows for sure; there's insufficient detail to
know what their calibration/specification are in reference to but that
would be the logical surmise, yes. They claim a reference back to NIST;
however all that necessarily would imply would be a fixed target and
that it passed under those specific conditions. One would presume that
target would have an emissivity of 0.95.
For those applications where only a differential is needed absolute
accuracy isn't particularly important, true.
For the exterior house it'll probably work fine; for the location of air
leaks in the attic it may not be so good as you may not have a good
target. The basis for the differential being of value is that the
surface is consistent; if that isn't so you may not be so able to find
the hot spots particularly if it is simply an air path.
When it warms up a few degrees here in central New Jersey, I'll venture
into the distant bowels of the attic. Near its entrance (via pull-down
ceiling stairs), the duct temperatures were about what I'd expect (mid
50 degrees). Right at the pickoff points to the individual rooms, at the
fittings with the damper doors, temperatures were about 95F around the
circumference (attic ambient, 38F). But the square inches of all these
pickoffs are trivial - probably less than 1 percent - compared to the
overall surface areas of all supply and return ducts. There may be much
greater losses at questionable joints further into the attic.
Thanks, again, to all who responded.
It may be the unit, a Ray Tech works well. Cheaper units are not
accurate 3-5 degree + or - is common so you cant even test a room
accurately. Better units will have 1 degree + - accuracy and measure
metal, its the only safe and quick way to do it.
I have a copper/stainless pan like that. Some surfaces don't emit waves
very well. Your readings could be affected by cooler waves from another
surface being reflected off the metal.
I think I'd wrap it in a thin layer of tape and let the tape generate
I just bought a Ryobi IR/Sonic Measurer. I noticed the same problem with
pipes. Like others have said, it may be that it can't read accurately on
small round items due to reflection or some such. The IR gets scrambled,
much like radar on a stealth plane.
I also noticed that the Sonic Measurer doesn't work when aiming through
a narrow opening, or when there is a closer item to the path of the
Thanks, everyone, for your replies. They have been very informative.
I put a piece of black electrician's tape around the hot water pipe
closest to the heater's outlet; the temperature reading on the tape now
jumped to what I would expect, about 110F. I ignored the red laser
pointer and just held the reading portion of the meter about 1/4" from
the tape. On the shiny copper just above the tape, the reading was about
Someone asked how I measured the cold and how water temperatures. I used
a dial-type, quick-reading meat thermometer under running water from the
laundry faucet. I found, however, that if I point the IR thermometer
where the water hits the laundry tub, the two readings matched.
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