How to Develop Intelligent Blood Oxygen Monitor PCBA

In the modern health management system, pulse oximeters have become a focal point of public attention due to

 their convenient and efficient health monitoring features. 

From professional diagnostics in medical institutions to daily health care at home, as well as in scenarios such 

as sports fitness and sleep monitoring, pulse oximeters are ubiquitous. 

A pulse oximeter is a medical device used to measure blood oxygen saturation and pulse rate in the human body. 

It features a simple structure, ease of use, and straightforward operation, making it one of the commonly used medical devices.


Product Structure: A pulse oximeter typically consists of a blood oxygen sensor, a display screen, and a power supply. 

The blood oxygen sensor is responsible for measuring blood oxygen saturation and pulse rate, the display screen shows the measurement results, 

and the power supply provides the necessary electricity for the normal operation of the pulse oximeter.


Working Principle: The working principle of a pulse oximeter is based on the photoelectric effect.

 It uses the reflection and absorption characteristics of infrared

 and visible light to measure blood oxygen saturation and pulse rate. During measurement, the pulse oximeter sensor is clipped onto a finger. 

The light source inside the sensor illuminates the blood, and then the reflected light returns to the sensor. 

Sensors inside the probe detect the intensity of the reflected light, allowing the calculation of blood oxygen saturation and pulse rate.


Product Parameters:


The main product parameters of a pulse oximeter include measurement range, accuracy, display method, power supply, and power consumption.

 Here's a brief introduction to these parameters:


1. Display Mode: TFT screen display;


2. Blood Oxygen Saturation: Measurement range: 35%–100% (70%–100% is normal blood supply);


   ① Measurement Accuracy: ±2% within the range of 70%–99%, undefined for ≤70%;


   ② Resolution: ±1% for blood oxygen saturation;


3. Pulse Rate: Measurement range: 30BPM–250BPM; Measurement accuracy: ±3BPM or ±3% of the measured value;


4. Power Supply: 2 AAA 1.5V alkaline batteries;


5. Power Consumption: Less than 50mA;


6. Auto Power-off: Automatically shuts off 8 seconds after no finger is inserted;


7. Operating Environment: Operating temperature: 5℃–45℃


   ① Storage temperature: -20℃–60℃


   ② Humidity: 15%–80% during operation, 10%–80% during storage; Atmospheric pressure: 70kPa–106kPa.


Applicable Groups: Pulse oximeters are suitable for a variety of people, including the elderly, patients with cardiovascular diseases, 

and patients with respiratory system diseases. They are particularly helpful for individuals with respiratory diseases or sleep

 apnea syndrome by monitoring blood oxygen saturation, identifying potential issues in time, and taking necessary measures.


In summary, a pulse oximeter is a convenient and easy-to-use medical device that helps people better understand their health status and 

enables timely diagnosis and treatment when health issues arise.

Working principle of a pulse oximeter: Hemoglobin in human blood exists in two states

oxyhemoglobin (HbO₂) and deoxyhemoglobin (Hb). 

These two types of hemoglobin have different light absorption characteristics at different wavelengths. 

Typically, a pulse oximeter uses two light-emitting diodes (LEDs) with different wavelengths, 

one in the red light range (around 660 nm) and the other in the near-infrared range (around 940 nm).

 Oxyhemoglobin absorbs less red light and more near-infrared light, whereas deoxyhemoglobin absorbs more red light and less near-infrared light.

 When these two wavelengths pass through body tissues 

(such as fingers or earlobes), the absorption levels vary according to the different ratios of oxyhemoglobin to deoxyhemoglobin, 

resulting in differences in transmitted light intensity.

 A photodetector measures the transmitted light, converts the optical signal into an electrical signal, and sends it to the pulse oximeter's microprocessor. 

Developing a pulse oximeter PCBA (Printed Circuit Board Assembly) is a systematic engineering task that involves hardware design, 

software development, testing, 

and verification. Below is a detailed introduction to the steps to start development: 

- Define functional requirements: Determine the basic functions the pulse oximeter should perform, such as measuring blood oxygen saturation and pulse rate, 

displaying data, storing and transmitting information. Additional features could also be considered, such as alarms or exercise modes.

- Establish performance indicators: Set performance indicators for the pulse oximeter, such as measurement accuracy, 

response time, and anti-interference capability. 

These indicators will serve as an important reference for subsequent design and testing.

- Identify target user groups: Different user groups may have varying demands and use scenarios for the pulse oximeter. For example, 

medical professionals may prioritize measurement accuracy and data reliability, whereas general consumers may focus more on ease of use and device comfort. 

- Schematic design: Based on the results of the requirement analysis, design the PCBA schematic. This includes selecting appropriate microcontrollers, sensors, 

displays, power management chips, and other key components, as well as defining their electrical connections.

- PCB layout design: Translate the schematic into an actual PCB layout. During the layout process, 

factors such as component placement, 

routing rules, and electromagnetic compatibility (EMC) must be considered to ensure the PCB’s performance and reliability.

- Select appropriate sensors: The core sensor of a pulse oximeter is the photodetector used to detect the absorption of different light wavelengths by human tissue.

 Choose sensors with high sensitivity, low noise, and good stability, and ensure their interface is compatible with the microcontroller.

Power Management Design: Design a reasonable power management circuit to ensure that the PCBA can be supplied stably in different operating modes.

 Consider using low-power design to extend battery life.

Writing Drivers: Write drivers for hardware components such as sensors, displays, and communication interfaces to ensure they work properly. 

The drivers need to implement functions such as data collection, processing, and transmission.

Implement Measurement Algorithms: Develop algorithms for measuring blood oxygen saturation and pulse rate. 

These algorithms need to accurately calculate blood oxygen saturation and pulse rate values based on the data collected by the sensors, 

in combination with human physiological characteristics.

Design User Interface: If the oximeter is equipped with a display, a simple and intuitive user interface needs to be designed

 to allow users to view measurement results and operate the device easily. 

The user interface should have good interactivity and readability.

Data Storage and Transmission: Implement data storage functionality to save measurement results to internal memory or external storage devices.

 At the same time, support data transmission functions, such as transferring data to mobile phones, computers, and other devices via Bluetooth, USB, and other interfaces.

Hardware Testing: Conduct hardware testing on the PCBA, including electrical performance tests, functional tests, and reliability tests. 

Check circuit connectivity, 

power stability, and component operating conditions to ensure the hardware design meets requirements.

Software Testing: Test each module developed for the software, including unit tests, integration tests, and system tests.

 Verify the software's functional accuracy, stability, and compatibility to ensure it runs normally.

Overall Performance Testing: Integrate the hardware and software for overall performance testing. Simulate real usage scenarios to test performance indicators 

such as the measurement accuracy, response time, and anti-interference ability of the oximeter, ensuring the product meets design requirements.

Compliance Testing: Conduct compliance testing for the oximeter according to relevant standards and regulatory requirements, 

such as electromagnetic compatibility testing and safety performance testing. Ensure the product meets market entry conditions.

Prototype Production: Produce PCBA prototypes according to the design plan for small-batch production. 

During the prototype production process, promptly identify and resolve any issues that arise.

Production Process Optimization: Optimize the production process to improve efficiency and product quality. For example, optimize soldering 

and assembly processes to reduce defect rates during production.

Continuous Improvement: Continuously improve and optimize the oximeter based on user feedback and market demand. 

Continually enhance product performance and user experience to meet market competition needs.