A core temperature sensor is a medical device worn on the body to measure core temperature. They are designed to provide continuous temperature readings for up to seven days. When paired with a heart rate monitor, the core temp sensor can provide even greater accuracy of temperature readings. They can be worn on the body as a clip-on medical-grade adhesive patch or clipped onto a sports bra.
Resistive temperature detectors
Resistive temperature detectors (RTDs) are used to detect and record temperature changes in a variety of structures. They work by using a small metal wire wound in a coil or an etched grid on a substrate. As the temperature increases, the resistance of the metal increases. The resistance at a base temperature is proportional to the length of the element and the inverse of its cross-sectional area.
Resistive temperature detectors are commonly made from platinum wire wound around a ceramic bobbin. Compared to the thermocouple, they exhibit much more accurate and linear behavior. RTDs are more accurate and linear over a wider temperature range, and their linearization is easier than thermocouples.
Thermocouples
There are a variety of thermocouples on the market. The wire style sensor measures fluid temperature in an enclosed pipe or container. These sensors are useful for monitoring temperature trends over a short time span and for high-pressure applications. Probe style sensors are also available and use a thermowell. They must be warmed to the process temperature before they can begin collecting data.
Thermocouples are made of dissimilar metals and operate using the principle of thermoelectricity. The temperature gradient created by the temperature difference between two thermocouples generates a voltage. This voltage can then be translated to a temperature. However, it must be remembered that the cold junction is colder than the hot one, which limits their accuracy.
Surface mount temperature sensors
Surface mount temperature sensors are among the most widely used temperature-measurement technologies. They are a great choice for many industrial settings, from developing new products and refining manufacturing processes to reliability analysis and maintenance prediction. They are especially useful for applications that require the measurement of surface temperatures, such as motors and complex composite aerospace parts.
Surface mount temperature sensors offer several benefits over through-hole packages, including a smaller package size and a low-profile design. Furthermore, they are easy to assemble. Surface mount temperature sensors, however, tend to measure the temperature of the PCB rather than ambient temperature. This is due to the fact that ambient temperature measurement requires special layout techniques. Surface mount temperature sensors can also measure the temperature of a die.
Cold junction compensation
The basic concept behind cold junction compensation is to reduce the temperature difference between two thermocouples in direct contact. It is possible to do so by using a thermocouple that has a low pass filter (-3 dB at 10 Hz) at the junction between the two metals. To do so, a measuring device must be used, such as a transmitter or DCS input card. The measuring device should be able to automatically calculate compensation based on the type of thermocouple used in the measurement and can do so continuously.
The thermocouple is connected to a precision low-noise amplifier that can make gain, offset, and impedance adjustments to achieve the best signal. The amplifier then matches the conditioned signal to a multibit ADC, which sends it in digital format to a PC. From there, the PC can compute the actual temperature at the hot junction of the thermocouple.
