A Bi-Metal thermometer has two metal strips formed into a coil. Metal changes volume with temperature so the coil will tighten with cooling and unwind with exposure to heat thus turning the attached point. For accurate readings the entire expanse of coil must be exposed to the product you are testing. Bi-metal thermometers should also be checked for calibration if dropped, exposed to temperatures greater or less than the span of the dial, or other excessive uses. The Cooper-Atkins Corporation Bi-Metal Pocket Tests have an external dimple on the stem to indicate exactly where the coil ends and its appropriate insertion point.

To help monitor the temperatures of your equipment or food, Cooper-Atkins offers a variety of monitoring thermometers to fit you specific needs. Many have color-zoned dials and HACCP guidelines.