Keywords: temperature measurement, wearable, temperature, medical patches, wrist wearables, medical wearables, contact sensor, smart clothing, health sensing, bio sensing
This application note recommends how to add temperature measurements into a wearable product, either a wrist worn wearable, embedded clothing, or a sticky medical patch. The Maxim temperature sensors, such as the MAX30205, are integrated solutions that allow a direct connection to host micro controllers to read the temperature of the area that the sensor is physically in contact with. This application note also shows that integrating a temperature sensor in a wearable product requires very few components.
Figure 1. MAX30205 typical application circuit.
The Maxim wearable contact temperature sensors work by connecting the temperature measuring digital device to the target surface for temperature measurement. Temperature measurement with a clinical grade accuracy of ±0.1°C allows the user to have a good understanding of a person’s health and general well-being. The use of temperature measurements and other body vital signs (such as PPG and ECG) allows decisions about the user’s health to be made. Some companies assess the user’s core body temperature based on the skin surface temperature. Hence temperature is an important body vital sign in the growing marketplace of medical and consumer wearables.
The difficulty of measuring temperature in a wearable product is making sure that you are measuring the user’s temperature and not the temperature of the wearable product. Also make sure the electronics in the wearable do not influence the temperature measurement, making the measurement invalid.
Because of the complexity involved, designing the product requires some trial and error. Some protocols to test and confirm the temperature measurement must also be done before an industrial design is considered complete.
Consider the following recommendations and suggestions based on the use case of a wearable that is measuring the surface temperature of human skin: