If the minimum voltage of the sphygmomanometer can work at 4.5V, you need to install three batteries to work with the rechargeable battery of 1.2V, and then try to make the power supply work, because the four batteries can reach 4.8V. You can also use a 6V power adapter.
The principle of sphygmomanometer:
Electronic sphygmomanometer is a medical instrument that uses modern electronic technology and indirect blood pressure measurement principle to measure blood pressure. Electronic sphygmomanometer can be divided into arm type, wrist type and watch type; Its technology has experienced the development of the first generation (mechanical constant-speed exhaust valve), the second generation (electronic servo valve), the third generation (pressurized synchronous measurement) and the fourth generation (integrated gas circuit).
The first generation (mechanical constant-speed exhaust valve) technology is usually considered inaccurate because of the use of aging rubber valves, which has been eliminated by mainstream electronic sphygmomanometer manufacturers; Electronic sphygmomanometer has become the main tool for home self-testing blood pressure. Electronic sphygmomanometers are also increasingly used in hospitals and other medical institutions.