Development of thermistor based low cost high sensitive respiration rate measurement system using audio software with audio input

Clinical investigation of lungs can be find out by measuring respiration rate. Different methods are present to measure the human respiration rate like Respiratory Rate measurement using Piezoelectric Sensor, Measurement of Respiratory Rate using Laser Doppler Vibrometer, Respiration Rate Measurement System Using Pyroelectric Transducer, Impedance Pneumography Method, Measurement of Respiration Rate by Capnography and Respiratory rate measurement using PPG (Photoplethysmography) signal. However, all of these techniques are very cost effective. We have design a new system using NTC (Negative Temperature Coefficient) type thermistor and Wheatstone bridge and a differential amplifier using IC-741. This system can be used to measure the respiration rate along with display of its waveform in a computer screen. In this system the output signals is taken and after some impedance matching it is used in audio input to a computer. A freely available software Audacity (version 2.1.0) downloaded from internet and installed in to the computer to see the waveform of output signal. The used thermistor is highly sensitive which changes it resistance -7KΩ per °C rise in temperature.