Photoelectric heart rate measuring method for pig based on CC2541

ObjectiveThe paper aimed to develop a pig ear tag measuring heart rate which was based on the principle of photoplethysmographic(PPG) so as to realize the on-line monitoring of pig heart rate. MethodAccording to PPG prin-ciple, SoC chip CC2541, photoelectric pulse sensor and MPU6050 were used to develop a pig ear tag measuring heart rate based on CC2541 bluetooth 4.0 and then analyzed main source of movement interference for pig heart rate. Meanwhile, heart rate signals of human body simulating pig movement were collected and imported into MATLAB software. Fast fourier transform(FFT) was used to analyze effects of PPG signals, frequency domain of movement signals and low frequency sampling on the extraction of heart rate. FFT was transplanted into CC2541 and directly extract the heart rate. ResultThe relative motion between pig ear and sensor was the main internal cause in movement interference. When the clamping pre-ssure between pig ear and sensor was within the scope of 0.6-1.5 N, the sensor can output full PPG signal waveform. The ear tag could accurately obtain the heart rate when pigs were in static state, while the heart rate data was extracted effective-ly by FFT algorithm when pigs were in movement state. Under the limits of CC2541 RAM capacity, the ear tag could satis-fy FFT algorithm to extract the heart rate when using 128 sampling points. The heartbeat rate was 2.813 Hz treated by FFT in CC2541 so the pig heart rate=2.813 Hz×60 s=168.78 beat/min. The heart rate was 160.00 beat/min by manual measure-ment in static state. The two results were basically coincide. ConclusionHeart rate measuring pig ear tag based on CC2541 bluetooth 4.0 enjoys the characteristics of small size, strong anti-movement interference and low power consump-tion, which is suitable for long-term and dynamic monitoring of pig heart rate. It provides a new method for the study of pig health early warning, animal welfare, behavior modeling and others.