Abstract
We have developed a calorimetry sensor that can perform a local measurement of the surface heat dissipated from the human body. The operating principle is based on the law of conductive heat transfer: heat dissipated by the human body passes across a thermopile located between the individual and a thermostat. Body heat power is calculated from the signals measured by the thermopile and the amount of power dissipated across the thermostat in order to maintain a constant temperature. The first prototype we built had a detection area measuring 6 × 6 cm2, while the second prototype, which is described herein, had a 2 × 2 cm2 detection area. This new design offers three advantages over the initial one: (1) greater resolution and three times greater thermal sensitivity; (2) a twice as fast response; and (3) it can take measurements from smaller areas of the body. The sensor has a 5 mW resolution, but the uncertainty is greater, up to 15 mW, due to the measurement and calculation procedure. The order of magnitude of measurements made in healthy subjects ranged from 60 to 300 mW at a thermostat temperature of 28 °C and an ambient room temperature of 21 °C. The values measured by the sensor depend on the ambient temperature and the thermostat’s temperature, while the power dissipated depends on the individual’s metabolism and any physical and/or emotional activity.
Highlights
The main developments in calorimetry instrumentation have occurred in the area of thermal analysis, a field that has observed the construction of a myriad of devices that are only differentiated by the specific characteristics of the thermal process being studied [1,2]
The working principle for this small instrument is based on the law of conductive heat transfer and, as its operation requires a thermostat to reach a constant temperature, it can be classed as an isothermal heat conduction calorimeter [3]
We have developed a calorimetric sensor that can perform a localised measurement of surface heat dissipated from the human body
Summary
The main developments in calorimetry instrumentation have occurred in the area of thermal analysis, a field that has observed the construction of a myriad of devices that are only differentiated by the specific characteristics of the thermal process being studied [1,2]. This work presents a calorimetric sensor designed for localised measurement of surface heat dissipated by the human body. We attempt to measure the power transmitted by conduction using a thermopile placed between the human body and a thermostat maintained at a constant temperature. In this particular calorimetry application, the dissipation being measured does not occur inside the measuring device but rather outside it; this instrument does not, comply with normal calorimetry standards. The working principle for this small instrument is based on the law of conductive heat transfer and, as its operation requires a thermostat to reach a constant temperature, it can be classed as an isothermal heat conduction calorimeter [3]
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