The BP01 pressure sensor is a high-performance component designed specifically for monitoring blood pressure in portable electronic sphygmomanometers. It is built using a precision thick-film ceramic chip encased in a nylon plastic package, ensuring excellent linearity, low noise, and minimal external stress. The sensor features internal calibration and temperature compensation, which significantly enhance measurement accuracy, stability, and repeatability across the full scale. Within its operating range, the BP01 offers an accuracy of ±1% with a zero offset of no more than ±300μV.
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The working principle of the BP01-based sphygmomanometer involves several key circuits: a bias power supply circuit (A1, A2), a pre-processing circuit (A3–A6), a display circuit (A7), and the pressure sensor itself. This system can measure blood pressure in the range of 0 to 200 mmHg with a resolution of 0.1 mmHg. It operates on a 9V laminated battery.
The bias power supply circuit uses a dual operational amplifier LM10 with an internal reference voltage. A1 functions as a non-inverting amplifier, while A2 acts as a voltage follower. Together, they amplify the internal reference voltage (which is 200 mV) to provide a bias voltage (Vs) of 5V for the BP01 sensor. This is calculated using the formula: Vs = Vref × (1 + R2/R3).
The pre-processing circuit includes four op-amps (A3–A6). A3 serves as an offset correction circuit, while A5 acts as a buffer to isolate the output signal from the pressure sensor. A4 and A6 form a gain stage, where the gain AV is determined by AV = 1 + (R1/RT). The output voltage of this stage is given by Vout = 2 × (1 + R1/RT) × VIN, where VIN is the sensor’s output voltage.
The display circuit uses a three-and-a-half digit LCD driver. After amplification by the pre-processing stage, the sensor's output is displayed on the LCD screen, allowing users to read the measured blood pressure value.
To calibrate the device, the zero-voltage output adjustment is performed by adjusting the potentiometer RP1 until the sphygmomanometer displays 000.0. This ensures that the system is properly zeroed before use.
August 01, 2025