深圳市三联盛科技股份有限公司-彩客平台

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sensor accuracy should not be ignored in low-cost, large-scale sensor applications

2016-11-15

many research institutions predict that the market size of portable medical devices will reach about $20 billion in the next few years. among them, the market size of home care and medical equipment is expected to reach nearly 26 billion us dollars in 2022. the growth of market demand is mainly driven by mobile health monitoring equipment, personal oxygen generator and fixed equipment.
 
   in addition to home health care, smaller medical equipment is also required to transport patients in airplanes, helicopters and other space constrained situations. the smaller the equipment, the lower the manufacturing cost; the stronger the function, the higher the cost. advanced basic pressure sensors with the right level of accuracy provide a potential solution to these challenges. for example, in the health care market, more and more scientific and technological designs are striving not to interfere with people's lives, thus increasing the demand for miniaturized equipment. this trend is reflected in the oxygen generator, cpap ventilator and other equipment. in addition, space is the most valuable for medical processes that need to be carried out in small spaces, sometimes in remote areas. this means that traditionally bulky devices, such as ventilators, also need to be smaller.
 
   on the surface, there is a greater demand for smaller and more functional sensors than for sensing accuracy. however, in the case of fixed cost, the sensor accuracy should still be considered by manufacturers. only considering multi-function and sacrificing precision will bring bad results.
 
small volume, multi-functional sensor needs higher
 
   today, the demand for low-cost advanced basic pressure sensors is increasingly being submitted to oems in the vertical market. this means that for engineers who need to design and create low-cost, large-scale components in industrial manufacturing and health care, low-cost advanced basic pressure sensors have become a very valuable product. one of the most important factors affecting this demand is mobility.
 
   in the health care market, people increasingly hope that health care can be carried out without interfering with life, so the demand for smaller equipment is growing. this is reflected in the development trend of oxygen generator, cpap ventilator and other equipment. in addition, space is the most valuable and scarce resource for medical processes that need to be carried out in small spaces, sometimes in remote areas. this requires that traditionally bulky devices (such as ventilators) become smaller.
 
   the reduction of the volume of the equipment requires that the volume of the built-in components be smaller, and users also expect the device to be more functional. in the field of air pressure control, for example, the user requires that the device be as small as possible, but still be able to provide highly accurate readings. as a result, as these devices become smaller and more compact, there is an increasing demand for better functionality of components (e.g., sensors) themselves.
 
   of course, this is a dilemma. because higher precision often means higher price. this is not realistic for low-cost, large-scale applications. in higher cost applications, engineers can more easily decide whether to invest in higher accuracy based on error estimates. in the case of ventilators, for example, the cost of design and manufacture is about tens of thousands of dollars; in this case, if the price of a more expensive sensor (about $15) is less than 1% of the total cost, then the investment is entirely reasonable. however, when designing blood pressure monitoring applications, the design and manufacturing costs are only $40-120, so it would be unwise to spend $15 more to achieve the total error band of 1.5% fss.
 
   so how can we evaluate the accuracy level of low-cost sensors in a practical and economical way under a reasonable budget level? to create value from these types of applications, designers should not regard these components as commodities, but as key technical means that can bring competitive advantages.
 
   accuracy remains an important consideration in low-cost applications
 
   in order to achieve high precision, the price of sensors should be increased accordingly. however, it is not economical and can not meet the needs of low-cost and large-scale applications. engineers should not ignore the accuracy value of low-cost sensors just because they are not the optimal solution. this is important because design engineers have paid more attention to factors such as low power consumption, repeatability accuracy and reliability while maintaining budget and improving product specifications. low power consumption has become the most attractive selling point for end users. whether it is "low cost" or not, accuracy has become a differentiation advantage.
 

  taking the oxygen generator as an example, the low pressure and ultra-low pressure silicon sensors in the machine can detect when the patient begins to inhale, so as to effectively and efficiently realize oxygen supply, and minimize the waste of oxygen when the patient is not inhaled. this not only makes the oxygen generator smaller, but also makes the operation more efficient. and smaller device sizes also mean lower power consumption and higher portability.

  another key to the importance of precision in low-cost applications is that it is very beneficial to retain easy to install components. the advantages of plug and play technology may be completely offset by the low precision sensor technology, such as the advantage of plug and play technology to relax the specification requirements for other parts of the system. however, this advantage is of great value to engineers who are committed to meet the design requirements. for example, if engineers can measure pressure more precisely inside the oxygen generator, there may be no need to pay more attention to details elsewhere in the system, or make up for it. the market demand for low cost plug and play devices is increasing, which explains to some extent why sensors with amplification compensation function are more popular than non compensation sensors. sensors with amplification compensation function can be used directly without any additional changes, and have high interchangeability, calibration and temperature compensation functions. if asic (dedicated integrated circuit) with mv input adc (analog-to-digital converter) is not used, the amplifier circuit may be required for large non amplifier sensors with compensation function. in contrast, the sensor without compensation function can only provide the original sensor output, and some kind of compensation is needed in many applications.
 
   if plug and play solutions (such as sensors with full amplification and compensation functions) are used, no additional circuit and design time is needed to develop, so engineers can provide higher value. however, if the data provided is inaccurate, it makes no sense to all the benefits of plug and play solutions; the savings of simple installation may be offset by low-end performance. a sensor without compensation (total error band teb greater than 30% fss) is about $9, and the cost of a sensor with compensation (total error band teb of about 10% fss) is $10, while a full scale plug and play sensor (total error band teb is about 1.5% fss) costs $13. thus, it is necessary to improve the accuracy of these cheap sensors with additional circuits only if the cost of the components (excluding the time spent in design and calibration) is less than $4. through the above analysis, many engineers can realize that plug and play devices are actually the most cost-effective devices.
 
   practical application case: oxygen generator
 
in recent decades, the size of portable oxygen generator has been shrinking, so it is more convenient to be used in aircraft transportation. it is the smaller sensor solutions (such as basic pressure sensors with amplification) that enable equipment manufacturers (oems) to further reduce the size of these devices; high precision sensors enable portable devices to provide the same quality and comfort as "large, technologically advanced" systems in hospitals.
 
  considering the basic function of the oxygen generator, it needs to reduce the nitrogen content in the air, so as to improve the oxygen concentration delivered to the patient. the basic pressure sensor with amplification function can be used to monitor the pressure inside the sieve bed to achieve the oxygen level required by the patient. in addition, sensors in the oxygen machine can be used to detect when patients begin breathing, thus more effective and efficient delivery of oxygen. monitoring the patient's beginning to inhale with a pressure sensor helps minimize the waste of oxygen during the period of non inhalation. in this way, the oxygen generator can be smaller in volume and more efficient in operation. in addition, smaller device sizes also mean lower power consumption and higher portability. these factors will make the equipment manufacturer's products better than those of competitive products using low precision sensors.
 
other practical applications
 
  advanced basic pressure sensors with amplification (such as honeywell's basic amplified abp series) are mainly used for non corrosive, non ionized gases (such as air and other dry gases). the following options extend the use of these sensors to non corrosive liquids:
 
  l dry gas option: the input port is limited to non corrosive, non ionizing media (such as dry air, gas, etc.) and is not subject to moisture condensation. the gases available include media compatible with high temperature polyamide, silicone, alumina ceramics, silicon, gold and glass.
 
  l liquid medium option: use the same construction material, but protect ports 1 and 2 from non corrosive liquids. the bare electronic circuit on port 1 is protected by silicone gel coating. since port p2 itself has non corrosive liquid protection, this option is a wet / wet sensor, both ports can use liquid. compatible media include condensate, water and brine.
 
  health care applications that can be designed using these sensors include: blood analyzers, blood pressure monitoring, beds, massage machines, sleep apnea devices, urine analyzers, ventilators / portable ventilators, and wound treatment.
 
conclusion
 
   in order to make it easier for patients to get comfortable and high-quality health care services at home, it is the general trend that portable medical equipment will be smaller. and for professionals who need to provide medical services in difficult environments, these devices must also be more practical. however, both medical professionals and patients should not only pursue small size portability at the expense of functionality. although these devices with smaller size and lower cost can work with low-cost sensors, the accuracy of sensors can not be ignored. if the sensor accuracy is given higher priority, it will help equipment manufacturers to differentiate their product value in the future growing market and bring greater benefits.