Research On The Application Of Deep Body Temperature Sensor Based On Heat Flow Principle During Knee Thermotherapy

The monitoring of the deep body temperature at the human knee joint is very important for the treatment and rehabilitation of joint patients.In order to measure the temperature of the deep body in the arthritis.This paper is based on the principle of biological heat transfer and the single double-channel heat flow model.The method of improving the core temperature measurement technique is proposed.According to the characteristics of the knee joint,it is divided into 6 areas and arranged with sensor probes in 12 locations.The heat transfer experiment of human knee joint and sensor probe is simulated based on knee deep temperature measurement model.Firstly,In steady-state conditions,maintain the knee core temperature of 38℃,according to the temperature difference on both sides of the sensor and the temperature at different thickness of the knee joint,the relationship between the tissue depth and heat resistance of different parts and the heat resistance is analyzed by using the heat transfer equation.Secondly,a thermal therapy simulation model is established by maintaining a core temperature of 38 ℃.Specifically,by setting the point heat source,a deep heat therapy experiment of a high frequency heat therapy instrument is simulated.The deep temperature of the particular location is calculated by using the heat resistance against the location probe display temperature,and the resulting show that the error is within0.62 ℃.The cause of the error is analysed and the relationship between the heat therapy temperature and the heat resistance of the body tissue is obtained.Finally,Based on the simulation results,the heat transfer theory of knee joint is established and this theory is verified by heat plate experiments and human body experiments.In the thermal plate experiment,the sensor thermal equilibrium is established at about 7.7 min,with an average error of 0.15 ℃,and the source of error of the human experiment is analyzed.This kind of ergonomic temperature sensor based on simulation experimental theory may be used for continuous measurement of deep body temperature in knee joint patients.And then,the heat transfer equation in this paper requires the temperature value of the skin surface,in order to determine the skin temperature,in this paper,a wearable multichannel temperature monitoring system is designed by means of constant voltage Bridge circuit.The STM32F103C8T6 was taken as the CPU,NTC(negative temperature coefficient)thermistors as the temperature sensing component,ADS1256 as the temperature signal conditioning module,bluetooth as the wireless transmission module.Display device is designed by LABVIEW.A bridge circuit composed of NTC thermistors and resistors is used to collect eight-channel temperature signals.A 24-bit high precision ADC module is used to amplify filter and convert analog voltage signals and to access body temperature data.Then transmission the data to the computer through bluetooth.Meanwhile,a stein-hart equation is used to fit the temperature-resistance curve of NTC thermistors.The impact of environmental interference and uneven distribution of body temperature is reduced by the means of software and hardware.The measurement error of temperature sensor is analyzed.The experiment show that the resolution of the measurement system is 0.01 ℃,and the accuracy of temperature measurement can reach ±0.02 ℃.This system presents a new design scheme,which has strong stability and high practical measurement accuracy.The measuring circuit has the advantages of simple structure,low cost,low power consumption and small volume,and can be used in the system that needs precise temperature measurement.