For any of you that have a remote sensing thermometer I have the following
Are they accurate enough that I could trace out the 1/2 inch, 12 inches on
center, heating tubes in the concrete slab of my shop. I would start on a
cold day, turn on the heat and start probing in an area where I would like
to bolt down some machinery. It would seem that if I used one with a laser
pointer, it should work. Slab is 6 inches thick, and tubes are
approximately in the middle. The specs on these thermometers claim 0.2%
All opinions greatly appreciated.
I doubt these would work. There was something that was on the market a
couple of years ago, and probably still is. It is a liquid crystal
temperature sensing strip that you stuck across the kid's forehead.
Also, Edmund Scientific had larger sheets of the stuff. They have a
picture of someone making a color pattern after putting their hand on
the thing. So, it is quite sensitive over the temperature range of
interest, and it shows relative temperature DIFFERENCES over an area.
This will make it 100 times faster to find the cool spot between the
I stumbled across a website showing a thermograph of buried hydronic pipes.
The URL defeats me just now but I do remember that the difference between
the pipes and room temperature floor was no more than about 2 degrees F.
Based on this, I conjecture that resolution is much more important than
accuracy or precision. If your remote thermometer will easily resolve (say)
0.1 degree F, I would guess that it would work a treat in locating hydronic
pipes buried in concrete.
OTOH, if you can borrow a thermal camera, you would get your information
Most of them seem to have about a 1:6 spot size: that is, they average over
a spot whose diameter is 1/6 of the distance from the sensor to the target.
So if you're 1' from the floor, you've got 2" resolution. There are some
that have a tighter focus than that. Make sure you know what you're
Have you tried something as simple as turning up the heat, mopping the floor
with some water and seeing where it dries first? Might work.
The resolution and precision (repeatability) of the
instrument will be more important than the accuracy in
discriminating small differences in the temp of the
concrete, and the difference will be very small. If the
thermometer is sensitive enough, and you take enough (many)
measurements, and record them on a grid so you can get a
visual sense of how the temps trend, it might work. But
that's essentially what the IR imaging device suggested by
others would do automatically.
The suggestions to dampen the floor and look for the
pattern of the tubing in the drying floor just ain't going
to work unless the tubing is a lot closer to the surface
than you think. My shop floor is exactly the same
arrangement as yours. It'll get damp a couple times every
summer in especially humid weather, and I'll turn the heat
on for an hour to bring the slab up a few degrees. In ten
years I've never seen an image of the tubing on the floor
as it dries.
Would a stud sensor work? Concrete is admittedly pretty dense, but
maybe there's enough change when you come to one of the pipes that it
would pick it up.
Not sure if there are metal detectors with a narrow field of
detection, but wouldn't that work as well?
I wonder if there's any way to make the pipe "magnetic" so that
something iron you run across the floor would be attracted to each
Run a sound run into the pipes and pass a stethoscope over the floor
looking for the loudest spots?
RWL ******* Remove NOSPAM to reply *******
The sensors that the gas companies use to locate pipes prior to
digging will work well if the pipes are metal. My neighbour is a
plumber and has such an animal. I'm not sure of the name but one half
of the box is clipped to any pipe, the other half is the locator, with
audiable tones and a sensitivity setting. You may be able to rent one
if you don't know a friendly plumber/drainage contractor.
I've played with this toy before and I'd guess accuracy is within half
an inch of center.
been doing this sort of thing for 25 years, one way or another (i am a
radiant heat installer). some tricks are;
your IR thermometer idea works well most times, but re-bar,
differences in slab thickness or tube height , uneven insulation , or
other objects can fool the thermometer.
a spray bottle of water works sometimes, if the atmosphere is right it
will evaporate a little quicker right over the tubes, sometimes. Real
cheap way to go.
if there are no splices in the system you can blow a magnetic ball
bearing through the system and detect it with a compass or mag flux
sensor , sometimes. Be careful , this trick can backfire if bearing
gets jammed. Nice part of this trick is that if there is a leak , and
you put the system under air pressure, the bearing will be drawn to the
leak by the escaping air. this trick once saved a 1/4 million dollar
marble floor from the jackhammer.
a electrical snake can be inserted into a 3/4 inch or 1/2 inch PEX loop
, how far depends on the turns. Then energize the snake with lots of
electric and trace it down. once you have any line traced, the other
lines can be estimated as 12 inch OC. this has worked for me many
times, and I now carry an electricans cable tracer to make it very
most times a good guess works well also, the odds are with you by at
least 12 to 1 per hole , and if you guess wrong it is no big deal to
hammer out a section of floor and patch the pipe.
Ivan, tell us where you are. If you're near the Twin Cities in Minnesota,
I'll bring my IR camera and we'll see if it works on this application. My
engineering unit can distinguish about 0.1 C differences; I don't think
accuracy matters for this project.
Disclaimer: I write much of the software for a line of IR cameras which I'll
not advertise here.
Pete (in St. Paul, MN)