What is a thermometer?
A thermometer measures temperature. AcuRite offers three types of thermometers; tube thermometers, bi-metal coil thermometers, and digital thermometers with thermistors. Here is an overview of all three types:
Tube Thermometers: A tube thermometer’s operation is simple; as temperature increases, liquid contained at the bottom of a glass tube expands, making it rise upward. As temperature decreases, the
liquid level falls. A gauge alongside the tube translates the liquid level into a temperature reading.
Instead of mercury, AcuRite’s tube thermometers are filled with 99.7% coal oil and 0.3% red pigment. This combination delivers accurate, reliable performance. It’s also safe in the event the thermometer is
Bi-Metal Coil Thermometers: As the name implies, the design of a bi-metal coil thermometer centers around a coiled metal strip. The strip is actually two plies of metal, with each ply made of a
different, specially-selected type of metal. The two metals were chosen because they expand at different rates when temperature rises. The outermost ply will be made of a metal that expands at a faster rate than the
inner ply. This creates a “push-pull” between the two strips. In other words, as temperature increases, the outer strip will be trying to unravel the coil while the inner strip will be pulling against it,
trying to keep the metal more tightly coiled. The amount the coil unravels will be mechanically translated into a temperature reading on an analog dial. The more a coil unravels, the higher temperature reading.
Digital Thermometers with Thermistors: All of AcuRite’s digital thermometers and weather stations measure temperature using a device called a thermistor. Thermistors are thermally sensitive
resistors which change in electrical resistance as temperature rises or falls. To put it another way, the thermistor has an electrical current flowing through it. Depending on the temperature it’s exposed to, the
thermistor will make it easier or harder for electricity to pass through…sort of like putting a kink in a garden hose to reduce the flow of water. There are two types of thermistors:
- Negative Temperature Coefficient (NTC) thermistors exhibit a decrease in electrical resistance when subjected to an increase in temperature.
- Positive Temperature Coefficient (PTC) thermistors exhibit an increase in electrical resistance when subjected to an increase in temperature.
The amount of electrical resistance applied by the thermistor will be electronically translated to a temperature reading on the thermometer’s digital display. Thermistors are especially useful because (depending on
the model and specifications) they can measure temperatures ranging from -100° to more than 600° Fahrenheit. They are also extremely precise over their entire temperature range, resulting in accurate, reliable