Terminology » Other Wireless » Blood Pressure Sensor: Basics, How it Works, and Interfacing

Blood Pressure Sensor: Basics, How it Works, and Interfacing

sensor pressure measurement arduino medical device

This page will cover the basics of blood pressure sensors, including their features, specifications, and how they work.

Introduction

When your heart beats, it contracts and pushes blood through your arteries. This force creates pressure on the walls of your arteries. Blood pressure is essentially a measurement of that pressure.

Blood pressure is recorded as two numbers: systolic pressure over diastolic pressure (e.g., 120/80).

What is a Blood Pressure Sensor?

Definition: A blood pressure sensor is a device used to measure the blood pressure in your body.

Regular blood pressure monitoring is crucial because high blood pressure can lead to serious health issues like heart attacks and kidney disease. Importantly, high blood pressure often has no noticeable symptoms, making measurement the only way to detect it.

Blood Pressure Sensor

The image shows a blood pressure sensor from Sunrom.

The instrument used to measure blood pressure is also known as a Sphygmomanometer.

The table below outlines blood pressure level categories and their corresponding values:

IndicationSystolic (mm/Hg)Diastolic (mm/Hg)
Hypotension<90<60
Desired90-11960-79
Prehypertension120-13980-89
Stage 1 Hypertension140-15990-99
Stage 2 Hypertension160-179100-109
Hypertensive Crisis>=180>=110

Technical Specifications (Sunrom Product Code 1437)

Here are the technical specifications for the Blood Pressure Sensor (product code 1437) manufactured by Sunrom, Gujarat, India:

  • Operating Voltage: +5V, 200 mA regulated
  • Wire Length: Approximately 2 meters
  • Output Format: Serial data at 9600 baud with 8 data bits, no parity, and 1 stop bit (ASCII format).
  • Output Parameters: Systolic, Diastolic, and Pulse Rate Readings
  • Sensor Pins: Tx-OUT, +5V, and GND

Blood Pressure Sensor: Working Operation

The blood pressure sensor provides output in an 8-bit ASCII format, ranging from 000 to 255. The three parameters – systolic, diastolic, and pulse rate – are separated by commas and spaces. The last byte of each data packet is always 0x0A in hex (or 10 in decimal), which represents a newline character, allowing you to view each reading on a new line in a terminal.

Let’s break down how to use a blood pressure sensor:

  1. Proper Positioning: Sit comfortably in a chair with both feet flat on the floor and your back straight. Rest for about 5 minutes before taking a measurement.
  2. Arm Placement: Place your arm at heart level (roughly chest level) and remain still and silent during the measurement.
  3. Cuff Placement: Wear the measuring cuff midway between your elbow and shoulder.
  4. Measurement: Turn ON the meter. It will provide readings within a few minutes.
  5. Data Display: The sensor can also be connected to the RS232 port of a computer to view readings using terminal software.

Blood Pressure Sensor Interfacing with Arduino

The following diagram illustrates how to interface the blood pressure sensor with an Arduino board:

GSR sensor interfacing with arduino

Note: Although the image is labeled as GSR sensor, the wiring connections are conceptually the same.

Here’s the pin connections between the blood pressure sensor and the Arduino board:

  • Vcc (Blood Pressure sensor side) - 5V (Arduino side)
  • GND - GND
  • Tx-OUT of blood pressure module - RxD pin of Arduino or microcontroller

Refer to dedicated tutorials on Blood Pressure sensor interfacing for specific Arduino source code examples.