In the test kitchen, we use hands-free clip-on digital thermometers to monitor temperatures when deep-frying food, making candy, and—with some models—checking food as it cooks in the oven without needing to open the oven door. We tested four models, priced from $24.99 to $59. Three have probes that clip onto a pot, with a wire that transmits readings to a small countertop receiver. The fourth is a single unit that clips on entirely.
We made French fries, fried chicken, and caramel sauce, evaluating the thermometers for accuracy, functionality, and how well they fit a variety of pots and pans, from 1-quart saucepans to Dutch ovens. To confirm accuracy, we double-checked each reading with two additional laboratory-quality calibrated thermocouples. The three models with separate wire probes can be used in the oven, too, so we put them to another test: roasting pork loins. (The fourth model is for stovetop use only.)
Our final test was aimed at durability. Sous vide cookers are designed to hold water at a specific temperature for many hours, so we inserted the probe of each thermometer into the sous vide and recorded their displayed temperatures every 30 minutes for 5 hours. Then we checked the recorded temperatures against the machine’s readout and results from an additional lab-quality thermometer.
Accuracy is paramount, as anyone with a faulty thermometer knows. A few degrees in the wrong direction can spell scorched sugar or soggy fried chicken. But our numbers were befuddling: Two models were off when we made caramel, yet in the sous vide cooker—and for one model that also works in the oven, when we did the pork loin test—they were perfectly on target. What gives?
Experts told us that a thermometer can be inaccurate for many reasons, including heat or moisture damage and poor quality control during manufacturing. Also, as with our sometimes-faulty thermometers, they may work in a consistent environment like that of a sous vide or an oven roast but aren’t responsive enough to report quickly rising or falling temperatures with accuracy.
Of our two accurate thermometers, one was a basic model with a timer, simple controls, a programmable alarm that rings when you’ve hit your goal temperature, and a probe that fits securely on a variety of pots and pans as well as in an oven roast; it’s our Best Buy. But for the Cadillac of clip-on digital thermometers, nothing beat the accuracy and user experience of our winner. Its slightly wider keyboard, with buttons for every function, was so easy to use that we didn’t even need the manual. Its high- and low-temperature alarms, with adjustable backlight and volume, were useful and well designed. It has the highest maximum temperature, 572 degrees, of all four models, which is nice for the oven and grilling. Most importantly, it's the only thermometer in our lineup that can be recalibrated so that it stays accurate over the long term, just as professional thermometers do. It’s more expensive, but its accuracy, easy interface, and promise of longevity are well worth it.