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Update 3 March 2015: Using a tub of ice in water for a freezing point reference (32⁰F) and simmering water for boiling point (210.5⁰F at 800 feet above sea level) — The temperature fluctuated a few degrees around approx. 29⁰F (or about 10% low) for the cold test, and it fluctuated around 211⁰F (expected). I do not know what was causing the fluctuations unless there were emissivity issues or real temperature fluctuations as my aim with the laser moved around a bit. Or maybe it was surface air temperature differences affecting the infrared view. This device accomplishes what is needed for temperature measurements that do not require a high degree of precision; e.g., finding cold drafts in one's home and many other uses.
This thermometer gun was helpful to me the very first time I tried it. It has always felt cool in the winter in our home, even with the thermostat set at 73⁰. Dr.Meter reported the temperature of a variety of objects in the house of different materials at about 69⁰. Interesting. But an indoor thermometer near the thermostat reports the temperature as 74⁰. So the mystery continues until I get a thermometer known to be accurately calibrated. Still, it sure doesn't feel like 73⁰, so right now I am more inclined to believe Dr.Meter.
Without a standard against which to compare its accuracy, I have to take its accuracy on faith. Subjective testing was illuminating. I at least got consistent results when I aimed at materials that seemed to be of the right type for the emissivity ratings for which this device is calibrated.
Accuweather reports the temperature where I live at 38⁰. So I went into the garage and had fun laser aiming at a number of materials and objects (concrete, floor mat, cardboard box, etc.), being careful to take into account the spot size for the distance from what I was measuring. And, indeed, the objects showed temperatures of 38⁰ plus or minus about half a degree.
Note: Dr.Meter has a spot size ratio of 12:1, meaning, the object being measured must be at least one inch in diameter when the meter is 12 inches away. At 12 feet the spot size must be at least 1 foot in diameter. A convenient reminder of this is stenciled as an image onto the side of the gun.
Temperature range spec: -58⁰F to 1022⁰F
Emissivity: 0.95 fixed
I had difficulty finding objects in my refrigerator or freezer that have the needed emissivity. I conclude that based on the wide range of reported temperatures. The measurements I was inclined to believe showed my freezer at about 0⁰ and my refrigerator at about 50⁰. According to the U.S. Food and Drug Administration, the refrigerator temperature should be kept at or below 40° F (4° C). The freezer temperature should be 0° F (-18° C). So we apparently need to drop our fridge temp....which I just did. I put a paper towel in the middle of the fridge to serve as a "trusted" material. It reported being at 72⁰ when I pulled it from near a warm oven. I was a bit startled to see it drop to 55⁰ within seconds of being put in the refrigerator. I wonder if the circulating air was being measured by the meter's IR sensor. In any case, I'll be able to see a relative drop in temperature of that material and others in the fridge after the fridge has had time to settle to its new cooler setting.
As another subjective test, I measured banana bread that had recently come out of the oven in several miniature bread pans. It was interesting to see how the cooling varied among each of them, ranging from 102-108⁰ and 84⁰ for the bread that had been pulled out of its pan and had been partially cut to eat.
Minimum/maximum temperature: The meter constantly adjusts as the aim is moved around. And in some cases temperature can vary quickly during a measuring period. So it was also handy to have a mode button that reported the highest and lowest temperatures encountered during the measuring session.
I didn't see it in the documentation, but the gun also has openings to install a strap that has a string loop.
I found it awkward to pull the trigger and at the same time push settings buttons. I just started using my other hand to press the buttons. Unfortunately the device defaults to Centigrade, so I had to push the button to change it to Fahrenheit for every measurement that I took. Similarly every time I wanted the laser to be on, but that is best set to off as default.
The tiny manual that comes with the device was written by someone for whom English is a second language. For other products sold by Hisgadget, this has not been a big issue. But for this device, the explanations were sometimes very confusing. I just figured it out by using it.
Above I reported an issue with having to change the C/F⁰ each time a measurement is made, but for infrequent use this is not a big deal. The 12:1 spot ratio seems to be fairly standard, though some can be as high as 50:1 or more. But other products cost a lot more. For example, the Fluke-62 costs $115 street price but has a lesser specs: spot ratio of 10:1 and a temperature range of -22⁰F to 932⁰F. At 20 bucks, the Dr.Meter is an amazingly good deal.
Now to go around our home to find leaks letting in cold air.