Medical sensor technology dominates the modern health equipment

Last Update Time: 2019-05-28 13:50:35

When patients enter the hospital today, they not only have to face doctors and nurses, but also face a series of advanced medical diagnostic and analytical equipment. Many devices are used to monitor their physiological parameters, such as body temperature, heart rate, blood pressure, blood oxygen. Level and so on. At the junction between the patient and these medical devices is a series of highly reliable and accurate sensors.

 

Industry research firm Marketsandmarkets predicts that the compound annual growth rate (CAGR) of the medical sensor market will be 8.5% from now until 2022, and the market size will reach $15 billion by 2022. There are many other similar trends and technologies in the industry that are driving this market growth, including increasing pressure on healthcare providers to further reduce operating costs. At the same time, the global population is aging, and consumers place high expectations on telemedicine.

At the sensor level closer to the patient, the continued development of MEMS, nanotechnology, ultra-low power sensors, wireless charging and new communication protocols can have a major impact. In addition, medical device designers are paying attention to sensor fusion and the development of multi-sensors that may offer more application space in the future.


Monitoring vital signs

Single-function sensors for sensing parameters such as pressure, temperature and airflow can be used in a variety of medical devices, from simple temperature measuring devices, blood pressure monitors and infusion pumps to magnetic resonance imaging (MRI), ultrasound, X-ray and Continuous medical equipment such as positive airway ventilation (CPAP).

Omron's D6F-01A1-110 high precision MEMS flow sensor can be used in breathing and ventilator equipment, anesthesia conveyors and oxygen concentrators. The device provides airflow measurement over a flow rate range of 0 to 1 liters per minute with an accuracy of ± 3% full scale. Similarly, Honeywell's HAFBLF0400C4AX3 high-precision airflow sensor provides flow measurement in the 400SCCM range with an accuracy of 2.5%. The sensor features an advanced onboard Asic for full calibration and temperature compensation for anesthesia and treatment of sleep apnea and nebulisers.

 

Among the most important medical pressure sensors, Amphenol's P162 is a board-mounted piezoresistive device capable of measuring pressures up to 300mm Hg. This compact sensor uses a 1150μm x 725μm chip and plays an important role in applications such as intrauterine pressure (IUP) measurements.

Like pressure and airflow sensors, temperature sensors are also a key component of a variety of medical devices. For example, Maxim's 700-DS600U temperature sensor operates from -40°C to 125°C with an accuracy of ±0.5°C. It can be integrated into an infusion pump for delivering fluids, drugs or nutrients to patients, as well as various forms of in vivo treatment. Maxim's portfolio also includes the MAX30205MTA+, which has an accuracy of ±0.1°C over the 0°C to 50°C operating temperature range and uses a high-resolution sigma-delta analog-to-digital converter (ADC) to measure The analog temperature is converted to a digital format that meets ASTM E1112 clinical temperature specifications when soldered on the final pcb. The sensor is suitable for body temperature measurement in medical environments and is suitable for body temperature measurement in fitness trackers. To continuously monitor body temperature in preterm infant incubators, Amphenol developed the MA300TA103C, a 9.52mm diameter biomedical NTC thermistor that operates from 0°C to 50°C.


Non-contact temperature measurement is a common application for temperature sensors such as the Melexis MLX90614ESF-BAA-000-TU. The MLX90614ESF-BAA-000-TU is an onboard infrared (IR) temperature measuring device consisting of two chips, including an infrared sensitive thermopile detector and a signal conditioning ASIC. The multichip sensor can be used at -40 °C~ Temperature measurement was carried out at a temperature of 85 ° C with an accuracy of ± 0.5 ° C.

 

Sensor fusion and multi-function sensor

In complex medical devices, although sensors with different functions have become commonplace, and more and more sensors need to be deployed in order to achieve better results. Just as the human brain integrates many different sensory inputs, such as smell, taste, touch, vision and hearing, to provide a better overall experience, technological advances can also combine input data streams from multiple sensors to achieve Sensor fusion.

Sensor fusion typically consists of three successive phases: data acquisition, feature fusion, and final decision consolidation. In the first phase, multiple sensors collect different types of signals, such as physical, chemical, biological parameter features or images. In the next phase, the collected signals are processed to extract relevant information and eliminate noise. Finally, the third phase performs data fusion through a series of decision algorithms.


A typical example of a sensor fusion implementation is a 9-axis 9-SFA system currently in use that includes a 3D accelerometer, a 3D gyroscope, and a 3D magnetometer. Each of the three sensors is capable of providing unique inputs, but with some operational limitations. For example, accelerometers provide x-axis, y-axis, and z-axis motion sensing, but are very sensitive to vibration. Similarly, gyroscopes can perform pitch, roll, and yaw rotation sensing, but are susceptible to zero bias drift. Although magnetometers provide x, y, and z-axis magnetic field induction, they are subject to electromagnetic interference (EMI). However, through data fusion, these sensor functions can be combined to obtain rich sensing data for a wide range of medical applications.

STMicroelectronics' SensorTile (STEVAL-STLKT01V1) is a 13.5mm x 13.5mm "turnkey" sensor fusion development board with one MEMS accelerometer, gyroscope, magnetometer, pressure sensor and a MEMS microphone (see Figure 1), the development board is equipped with a Stm32L4 32-bit ARm Cortex-M4 microcontroller. Similarly, NXP's FXOS8700CQR1 is a single package consisting of a 3-axis accelerometer and a 3-axis magnetometer with an optional i2C or point-to-point SPI serial interface with 14-bit accelerometer and 16-bit The magnetometer ADC resolution provides dynamic selectable full-scale acceleration ranges of ±2g, ±4g and ±8g, and a fixed magnetic field measurement range of ±1200μT. The main applications of this sensor in the medical field include patient monitoring, fall detection and rehabilitation.