Remote sensing thermometer question

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 pipes.
Jon

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 faster.
--Winston

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 getting.
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.

Or chop up some ice cubes with a blender, spread the resulting 'snow' on the floor and see where it melts first.

I think an IR sensor camera would be a first try. See if you can find somebody who does that sort of sensing to measure house insulation efficiencies.
Jim

Spray floor evenly with water. Watch where it evaporates first.

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.
Ned Simmons

Or call any industrial electrician and ask who they use to do the thermal imaging of installed equipment.

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 pipe.
Run a sound run into the pipes and pass a stethoscope over the floor looking for the loudest spots?
RWL
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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.
Good Luck.

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 easy.
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)