This is truly the gadget every one likes. Whenever I'm doing product demonstrations, it's the surface thermometer that is the favorite toy. The last couple of years have brought down the price significantly along with instrument choices. My first offering was by Fluke, which is very well known electronics instrument builder and the model I sold was over $300.00. Now, just under a $100.00 buys you a great model that includes a laser pointer.
A surface thermometer reads the surface temperature of anything its pointed at and is able to switch from Celsius to Fahrenheit. Laser sighting allows you to read the exact point and the temperature is instantly displayed in a LCD screen. The back-lit screen feature is preferred by horse people because you can use in low light or at night. To use: select a target and point. The smaller the target, the closer you should be to it. When accuracy is critical, make sure the target is at least twice as large as the spot. As the distance from the object increases the spot size of the area is measured by the unit becomes larger. ie: Your reading 1" spot if your 8" from the target, your reading a 2" spot if you 16" from the target and a 3" spot at 24" from the target.
So, just how do horse people use them? Some call surface thermometers the poor mans scanners or mini thermographer. I first heard the name Scanners by owners of the Acuscope equipment (microcurrent stimulators) that owned early models of surface thermometers. The readout was a red, yellow, and green system with some noise and colored lights on the little black box to indicate the hot spots. Because they scanned over an area looking for hot spots they were called scanners. A Thermographer is an imaging technique that assesses temperature with a color images. As such it can be used to detect heat or a 'hot spot', and since heat is one of the cardinal signs of inflammation it can be used to detect injury at very early stages.
Apparently those using surface thermometers have developed the knack to find specifics they are looking for. At the track they will scan the front legs looking for the slightest difference in heat. To do this effectively can be tricky. Surface thermometers are affected by; drafts, Sun Light, and change in the weather.
You must try to make equal comparisons. Say you are looking for front leg splints before they have surfaced. The action of a splint ready to "pop out" will create a small amount of heat that might not be noticeable by the touch. So, they use the surface thermometer to take numerous measurements over each front leg and compare the two. Being very careful to stand at the same distance and out of drafts for each measurement. The measurements should be similar; if over (5) degrees or higher they consider this suspect and treat accordingly. Well, you can see it doesn't take a genius to figure out this can be valuable information. Others have used them looking for heat coming from the hoofs or hock problems, shoulder and backs. Checking one of my horses with chronic wind puffs, it was easy to see which leg was having problems. The problem leg was measurably colder than the other. So if you can't afford expensive diagnostic tests a surface thermometer may be a worthwhile investment.