Cardiac current measurement; Every heartbeat of our human body will produce cardiac current, and the wireless heart rate chest strap is such an instrument that can sense cardiac current. The pole pieces of the sensor are located on both sides in front of the chest strap. After the user wears the chest strap, the pole piece in the chest strap collects the fluctuation amplitude of the exerciser's heart current, and then sends it to the heart rate meter through wireless transmission technology, which is converted into BPM value for easy observation. At present, this is the mainstream and a more accurate method to measure exercise heart rate. Its principle is consistent with that of ECG measurement. Another advantage of this method of measuring heart rate is that it can continuously measure heart rate during exercise. According to the types of sensing electrodes, wireless heart rate chest strap can be divided into traditional hard heart rate chest strap and new flexible fabric soft chest strap. The hard heart rate chest strap is made of conductive rubber electrode blocks embedded in the hard plastic strap. Flexible fabric soft heart rate chest belt adopts flexible film electrode and is welded on the flexible fabric belt by hot pressing. It is very light and comfortable to wear, which reduces the friction interference caused by the movement of the chest belt during exercise.
Photoelectric transmission measurement method; Photoelectric measurement is to measure pulse by using the change of hemoglobin absorbance in blood vessels. The watch is equipped with an infrared emitting beam loop and a receiving and reflecting loop. The advantage of this method is that it is very simple to measure the heart rate without a chest strap, but because the signal is very weak and easily disturbed by the outside world, the measurement data is inaccurate, so it is generally necessary to measure the heart rate in a quiet state, which is not suitable for continuous measurement of the heart rate during exercise. The green photoelectric measurement method consists of two light-emitting diodes with green wavelength and a photosensitive sensor, which is located on the back of the heart rate meter. The principle is based on the fact that the blood in the blood vessels of the arm will change its density when it pulsates, thus causing the change of light transmittance. The LED emits light waves with green wavelength, and the photosensitive sensor can receive the light reflected by the arm skin and sense the change of light field strength and convert it into heart rate. At present, MIO ALPHA, FITBOX HXM and Adidas SMART RUN heart rate meters in the United States all adopt this technology. The green photoelectric heart rate measurement completely abandons the heart rate chest strap, which can continuously measure the heart rate, calculate the average heart rate, record the maximum heart rate and set the heart rate alarm interval.