Abstract
This paper presents a system capable of measuring temperature and relative humidity with polymer optical fiber (POF) sensors. The sensors are based on variations of the Young’s and shear moduli of the POF with variations in temperature and relative humidity. The system comprises two POFs, each with a predefined torsion stress that resulted in a variation in the fiber refractive index due to the stress-optic effect. Because there is a correlation between stress and material properties, the variation in temperature and humidity causes a variation in the fiber’s stress, which leads to variations in the fiber refractive index. Only two photodiodes comprise the sensor interrogation, resulting in a simple and low-cost system capable of measuring humidity in the range of 5–97% and temperature in the range of 21–46 °C. The root mean squared errors (RMSEs) between the proposed sensors and the reference were 1.12 °C and 1.36% for the measurements of temperature and relative humidity, respectively. In addition, fiber etching resulted in a sensor with a 2 s response time for a relative humidity variation of 10%, which is one of the lowest recorded response times for intrinsic POF humidity sensors.
Highlights
Humidity and temperature monitoring are important in applications such as structural health monitoring (SHM) and pharmaceutical, medical, and food processing and storage [1,2]
In order to overcome some of the limitations of humidity sensors and to achieve a system capable of measuring climate parameters, this paper presents the development of a low-cost system for measuring temperature and humidity with polymer optical fiber (POF) sensors
This paper presented a POF-based sensor system for the measurement of temperature and
Summary
Humidity and temperature monitoring are important in applications such as structural health monitoring (SHM) and pharmaceutical, medical, and food processing and storage [1,2]. The human body can tolerate a wide range of temperatures and humidity, there are three general regions of human comfort that have been defined [3]. These regions are as follows: (i) comfort in temperatures in the range of 29–34 ◦ C with relative humidity (RH) below 70%; (ii) neutral comfort in relative humidity below 80% and temperatures between 27 and 36 ◦ C; and (iii) discomfort in temperatures lower than 27 ◦ C or higher than 36 ◦ C or in relative humidity higher than 80% [3]. Temperature and humidity sensors suitable for wearable robotics should be able to operate within these defined regions of comfort
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