How To Make ‘Automatic Blood Pressure Monitor’?


A blood pressure (BP) meter or a device used to measure blood pressure is available in a number of models, ranging from professional monitors used in health care facilities to inexpensive, portable monitors used in homes for one-handed application. Digital BP meters generally measure both systolic (peak pressure in the arteries) and diastolic pressures (minimum pressure in the arteries) by an oscillometric detection method, using a piezoelectric pressure sensor. The method uses a cuff to the upper arm and the pressures are determined automatically. To make the digital BP meter completely automatic, automatic inflation and deflation system is implemented using a microcontroller which executes control algorithms to monitor and regulate the cuff pressure. For accurate measurements, a low power MCU with some support for digital signal processing and a 10 bit or 12 bit ADC is generally required. An on-chip Real time clock (RTC) is required to store the value of Blood Pressure with timestamp. This is valuable for the patient and physician to track the variation during the course of the day and find the maximum and minimum. An integrated or external LCD display is used to show systolic and diastolic blood pressures simultaneously. To retrieve data from the device and analyze it offline, trend towards wireless connectivity which can be either blue-tooth or Wi-Fi, is upcoming.

Want to know more about BP monitors? Read the reference designs below which describe the complete hardware and software involved to build them.

  • Ultra Low Power Blood Pressure And Heart Rate Monitor: This reference design demonstrates a battery-powered, portable device to monitor blood pressure and heart rate that works in low-power mode displaying date and time. The device is easy to use with two buttons. To measure blood pressure, a ‘measure’ button is provided and to look at historical blood pressure, a ‘memory’ button is provided. The device can store 80 measured records in its EEPROM. The design leverages the features of the ultra low-power MCU MSP430F6638 with LCD to remain in standby mode and save power. More on this Reference Design
  • Wireless Blood Pressure Monitor: This reference design presents an intelligent and flexible handheld solution for arterial blood pressure measurement. The design is based on Flexis QE128 microcontrollers from Freescale that give the designers flexibility of expansion from low-end to high-end products. They allow designers to design one software and hardware platform for several projects in a modular way. A module can be added to create a new design. The software is non-blocking in which each module is treated as a separate task so that if one module stops running, others are not affected. The pressure variations in the cuff attached to the upper arm are used to produce the heartbeat signal. Using the heartbeat signal, a HCS08 determines the systolic blood pressure (SBP) and diastolic blood pressure (DBP). The system comes with many useful features like 4-language navigation menu, USB to download historical data, OLED display and wireless RF interface to communicate with other devices such as router. More on this Reference Design
  • Portable Blood Pressure Meter based on Low-power MCU: This reference design describes how to develop a low-cost, low-power, handheld or portable blood pressure meter with user interface. This design can measure both pulse rate and blood pressure using the system-on-a-chip PIC24FJ128GC010 MCU. The MCU uses eXtreme Low Power (XLP) technology and provides 18nA deep sleep mode. The MCU drives the pump by sending a PWM signal. The cuff pressure signal and the oscillation signal are derived from the pressure sensor and sent to the ADC of the MCU for measurement. The results for blood pressure and pulse rate can be sent to an integrated LCD, USB and wireless interface. More on this Reference Design
  • Low-cost Blood Pressure Monitor: This reference design explains the implementation of a blood pressure monitor in two ways. Both solutions use microcontrollers with one of them utilising a simpler design and more cost-effective. The first design uses a Renesas V850ES MCU which provides a signal to automatically inflate and deflate the cuff attached to the arm using a pump and valve. The signal of the pressure transducer in the cuff is provided to the ADC on the MCU to measure the pressure which, in turn, is used to calculate systolic and diastolic blood pressures. An LCD display is controlled by an external LCD controller. A USB port provides connectivity. The second design is a low cost implementation using Renesas 78K0R/Lx3 device which uses on chip ADC and DAC and an integrated LCD to reduce the external component count. An external USB or wireless device, provides connectivity. More on this Reference Design
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