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1
Technical Requirements of Analog Signal Path in Portable Medical Equipment
The challenge for companies committed to developing medical diagnostic equipment is to provide consumers with high-quality and low-cost products. In terms of reducing medical costs and improving patient care services, the most important thing is to reduce the volume and improve the accuracy of these medical devices. In today's increasingly serious problem of population aging, the above needs are more urgent. According to the imdica report of IMS research company, the total sales of consumer medical devices are expected to exceed US $5 billion by .
With the development and continuous improvement of the monitoring function of medical equipment, telemedicine providers can provide better diagnostic tools for home patients, emergency room paramedics and hospitals in several important areas of human health. Sphygmomanometers, blood glucose meters, defibrillators and other monitoring instruments need clear analog signals for accurate measurement, otherwise they may be life-threatening. The excellent design of analog signal path can help designers reduce the interference of external noise, expand the dynamic range and enhance the accuracy. In addition, in terms of component selection, designers must also choose carefully to meet the performance requirements of the final product.
High performance requirements in small packages
Previously, it was generally believed that medical equipment in hospitals and clinics was more accurate than portable instruments used at home. However, new technological trends are rapidly reversing this view. The users of the new portable medical devices are not only ordinary consumers, but also patients with deep scientific and technological understanding. Therefore, the needs of customers are no longer limited to taking body temperature, ECG and blood pressure. What customers need is a full range of nursing and measurement functions.
In order to meet people's urgent demand for home medical diagnostic instruments, equipment suppliers are relying on advanced inventory management and innovative design to enhance market competitiveness, and equip products with more functions to win more users. In the field of developing home medical instruments, one factor is very important, which is the development time required from the initial design to the real launch of the product. Shortening the time to market can enable manufacturers' products to seize the market. Whether the development cycle can be shortened depends on whether the design of system designers is flexible and cost-effective.
Process technology affects system design
Although electrical specifications are the main factor for designers to select components, the process used to manufacture integrated circuits is also important. For example, a typical blood glucose meter usually needs to be equipped with an operational amplifier with very low input bias current. Most designers will choose JFET amplifier. However, they should consider the temperature before making a decision.
Because JFET has a very low initial input bias, it is vulnerable to temperature changes. For every 10 C rise, the input bias will approximately double. To calculate the drift of the input bias, use the following formula (reference 1).
Ib(T)Ib(T0) x 2(T-T0)/10
For example, a JFET Input Operational Amplifier (such as National Semiconductor's lf411) has an input bias current of 50pA at 25 C, while a better option is National Semiconductor's lmp, which is a bipolar input operational amplifier with an input bias current of 1.5na. Through the above formula, we can quickly calculate that the input bias current of lf411 becomes 3.2na at 85 C, which is twice that of lmp.
Trade off of evaluation system
Speed, noise and power consumption may be equally important for some designs. A low-noise device will consume more current, while a low-power device can only provide limited bandwidth. One way to overcome these problems is to use inverse compensation amplifiers in appropriate applications. Compared with the stable unit gain and high speed, the advantage of the anti compensation amplifier is that it can provide a large bandwidth without affecting the power consumption.
Inverse compensation operational amplifier is most suitable for current voltage conversion (transimpedance) circuit. In medical instruments, one of the most common applications is to measure the oxygen content in blood cells, which is called SpO2 or saturated or peripheral oxygen. Figure 1 shows the block diagram of SpO2 module, in which the anti compensation amplifier (TIA) is used to convert the current from the photodiode into voltage.
Figure 1 typical block diagram of SpO2 module
Use shortcuts to shorten design time
The most important parameter of medical instruments is noise, which can cause serious interference to the circuit itself and nearby equipment. Calculating noise is a tedious task, especially when you want to calculate the overall impact of signal path on signal-to-noise ratio from power supply, amplifier, data converter and external components.
Generally speaking, medical instrument circuits tend to work at a lower frequency, so the designers of these systems usually pay more attention to the noise in the frequency band of 0.1 to 10Hz, also known as peak to peak noise. Unfortunately, some data sheets do not provide time domain noise (peak to peak) values, but only typical charts of voltage or current noise density. In addition to waiting for the circuit supplier to provide measurement data, there is a fast method to help calculate the peak to peak noise.
Suppose you intend to use lmp of national semiconductor to calculate the noise of peak to peak (0.1 to 10Hz) voltage. First, select a point in the frequency range within the specified frequency band, such as 1Hz, and the value in the comparison curve is 5.1nv / Hz (Fig. 2). Then use the following formula to calculate the root mean square value (RMS) of noise: Formula 1: ENRMS = "enf" ln (10 / 0.1), Where enf is the noise at 1Hz. The total root mean square noise of 10.9nv can be obtained through the above formula. If you want to calculate the peak to peak noise, you only need to multiply this root mean square value by 6.6 to obtain 72.2nv. The result of this estimation is quite good, which is close to the specification 78nv listed in the data sheet.
Fig. 2 Relationship between input voltage noise and frequency of lmp frequency and voltage noise
If the voltage noise density diagram in the data sheet does not represent the noise value at 1Hz, you can use the following simple equation (equation 2) to calculate the value at a certain frequency.
Where ENB is broadband noise (usually the value at 1kHz), and FCE is the 1 / F inflection point. As for F is the frequency of interest, in our case, it is 1Hz.
For example, the broadband noise of lmv851 of national semiconductor is 10nv / Hz at 10kHz. In order to calculate the root mean square noise, first determine the value of 1 / F inflection point (FCE) from the chart. Using the voltage noise density diagram in the data sheet, it can be found that FCE is approximately equal to 300Hz. Then, using the above formula, we can calculate en = 10 * (300 / 1) = 173nv Hz, which is the voltage noise at 1Hz. Finally, substitute this value into Formula 1 and multiply the result by 6.6 to get 2.4 Peak to peak noise of V.
Another consideration is current noise. Generally speaking, if the impedance of the power supply is not very large (> 100k ), you can still get a very close calculation result without considering the current noise, just like the above example. However, if the impedance of the power supply is large, the same technique must be used to calculate the current noise, and the voltage and current noise must be added in the form of root mean square value.
Requirements for determining speed
Just as the noise of operational amplifier is very important to the resolution of ADC, so is the bandwidth to maintain the accuracy of the system. In order to limit the error to 1 / 2 least significant bit (LSB), a fast check is needed to determine whether the bandwidth of the amplifier is sufficient. In addition to using complex and generic guidance, you can also use the resolution of the analog / digital converter to quickly calculate the results. The method is to use 1 / 2 (n / 2) and multiply the result by the amplifier frequency at - 3dB (reference 2).
Through the above shortcut and a 14 bit ADC, FEFF = 0. * f-3db is obtained in this example. For the operational amplifier (LMP) with configurable gain of 10 in Fig. 3, the frequency at - 3dB is 1.7MHz. In this way, the maximum bandwidth (at 1 / 2 LSB error) is equal to 0. * 1.7e6 = 13.3khz.
Fig. 3 block diagram of portable electrocardiograph
Monitor device and communication device
Most of the newer medical diagnostic instruments are equipped with wireless communication function. Modern electrocardiograph (EKG or ECG) can transmit patient data to doctor's clinic or hospital in a few minutes through personal electronic manual account (PDA) or other computer peripherals. Despite the benefits of wireless data transmission, such devices may cause serious interference to medical devices and make their readings wrong.
In order to avoid this interference, a filter must be used. However, adding filters will not only increase the volume of the equipment, but also increase the design cost. A more cost-effective and fast way is to use components (including filters) that can suppress radio frequency (RF) noise.
epilogue
Nowadays, the trend in the field of medical equipment is to provide consumers with higher value products, that is, home care instruments that are cheap and high-quality and can quickly provide diagnostic results. With the continuous progress of technology, more and more medical devices will transmit data from patients' homes to doctors' clinics in real time through computers. In addition, with the demand of users for more functions, the accuracy requirements for portable medical devices will be further improved to achieve more accurate diagnosis, which will rely on the continuous innovation, long-term development and commitment to comprehensive solutions made by designers.
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Hongke Will Continue to Launch a Series of Solutions for the Application of PCA in the Medical Equipment Industry
, including life science instruments, CT medical equipment, centralized control system and so on.
Centralized control, test and diagnosis of medical equipment in digital operating room based on Hongke PCA interface card
Digital operating room is the product of the development of computer information technology, biomedical engineering technology and modern medical technology. Using the digital port transformation of the existing equipment in the operating room, through digital network integration, the centralized control workstation controls the intraoperative medical equipment, and interacts with the network information inside and outside the hospital in real time. The schematic diagram of digital operating room is shown in the figure below.
Challenge
Problems faced by digital operating room
1. The number of medical equipment is large, and centralized control is difficult
In the existing operating room, there are many kinds of medical equipment, and the control panels of various equipment are quite different. Moreover, most of various operating room equipment are independent units, and there is no external unified communication interface, which brings compatibility problems. Secondly, the communication quality of centralized control is also directly related to the safety and efficiency of surgery. The communication between centralized control workstation and controlled equipment must be real-time, accurate and stable. To sum up, the centralized control of digital operating room is difficult.
2. Medical equipment is precise and expensive, and the maintenance cost is high
Medical equipment is complex and expensive. In case of communication failure, the equipment is generally replaced or waiting for professional maintenance. The corresponding failure causes are often unclear and the maintenance methods are not systematic, resulting in high maintenance time cost, high maintenance cost, resource waste and other problems. Therefore, it is necessary to introduce a set of effective medical equipment testing and diagnosis scheme.
programme
Centralized control, test and diagnosis of medical equipment in digital operating room based on Hongke PCA interface card
1. Centralized control
In order to realize the centralized control with high compatibility and security, can bus is selected as the communication protocol between equipment and equipment in the digital operating room and between equipment and main control. This requires the transformation of the digital port of the existing equipment in the operating room and the introduction of can interface, while the PCA interface card plays the role of "reformer". Its schematic diagram is shown in the figure below. PCAN can connect with medical devices through a variety of different interface types, such as USB, PCI, PCIe, minipcie, m.2, RS232, etc., quickly introduce standard can interface for medical devices and connect to can bus network. At the same time, the secondary development package provided by PCAN interface card can help developers flexibly realize the sending and receiving of can data, which is stable and reliable.
2. Test and diagnosis
Since the CAN bus structure is adopted to realize the construction of digital operating room, that is, the bottom sensors and actuators, medical equipment nodes and main control terminals are connected through can communication to realize information sharing and comprehensive management, a set of test and diagnosis system can also be developed for CAN bus, as shown in the figure below. The test and diagnosis system is based on PC and PCA, From bottom to top, it is composed of hardware, driver, software and application. Connected to the can network of the digital operating room through the can cable, the data of all nodes can be collected, and through data analysis and fault judgment, the current operation status of all medical equipment can be displayed intuitively, and the excitation signal can also be injected into any equipment node for function and stability test. As a can access point, PCA not only realizes the bottom can data transmission and collection, but also has the can fault prompt function. It is the bottom basic hardware to realize test and diagnosis. In particular, PCA can also enter the single listening mode to monitor the operation of the equipment as a listener, which will not have any impact on the can network, and can find and record intermittent faults in real time.
HONGKE
Key characteristics of Hongke PCA interface card
Key characteristics
Support can, can FD, J, CANopen and other physical layer and application layer protocols;
Support USB, PCI, PCIe, minipcie, m.2, PC / 104, PCI / 104, CPCI and other interface types;
Support windows, Linux and other operating systems;
Single channel, dual channel, four channel, six channel and other versions;
Provide upper computer software and secondary development package;
Operating temperature range: - 40 to 85 C
summary
The centralized control, test and diagnosis of medical equipment in digital operating room are realized through Hongke PCA interface card, which has the advantages of simple implementation, comprehensive functions, safety, reliability, real-time stability, and can solve the two difficult problems of centralized control and high test and diagnosis cost at the same time. At present, many manufacturers at home and abroad have used PCA interface card to upgrade their medical equipment. If you want to know more about PCA interface card, please contact Hongke for product information and trial opportunities.
Original title: [PCA medical application series] Part5 realizes centralized control, test and diagnosis of medical equipment in digital operating room based on Hongke PCA interface card
The source of the article: WeChat official account: Guangzhou Rainbow Electronics Technology Co., Ltd.] welcome to add attention! Please indicate the source of the article.
3
Application of DICOM Standard in Portable Medical Equipment
Application of DICOM standard in portable medical equipment1 IntroductionRadio frequency refers to the electromagnetic wave with a certain wavelength that can be used for radio communication. Radio frequency identification technology is a non-contact automatic identification technology rising in the s. It uses the transmission characteristics of radio frequency signal and spatial coupling (inductive or electromagnetic coupling) or radar reflection to realize the automatic identification of the identified object. However, at present, there are still many bottlenecks in the development of RFID, and the low data reading rate is one of the main bottlenecks.
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This paper will analyze the RFID system by introducing the basic composition and working principle of the RFID system. Combined with the problems encountered in the practical application of RFID system and the reasons for the low reading rate of the system due to the blind area in the reading range of readers, redundant data in different reading points, mutual interference of readers and other factors, this paper puts forward from the following aspects: reasonably optimizing the hardware configuration, perfecting the software design Play the role of middleware and integrate other technologies to improve the data reading rate of RFID system.
2. Basic composition of RFID systemRFID system at least consists of electronic tag (e-tag / transponder, also known as smart tag) and reader (reader / interleaver, also known as reader / writer).Electronic tag is the data carrier of RFID system. Electronic tag is composed of tag antenna and tag special chip. Electronic tags are divided into active tag, passive tag and semi passive tag according to different power supply modes; It can be divided into low-frequency electronic tag, high-frequency electronic tag, UHF electronic tag and microwave electronic tag according to different frequencies; It is divided into * label, linear label, paper label, glass tube label, circular label and special-purpose special-shaped label according to different packaging forms; According to their different working modes, they are divided into active tags and passive tags.
Reader is a device used to read or write electronic tag information. It can be designed into many kinds of products according to specific use environment and requirements. The reader communicates with the electronic tag wirelessly through the antenna, which can read or write the electronic tag identification code and memory data.A typical reader consists of a high frequency module (transmitter and receiver), a control unit, and a reader antenna. Of course, RFID system needs the support of computer and other hardware equipment and software in practical application. Figure 1 shows the composition of a typical RFID system.3 basic model of RFID system
The basic model of RFID system is shown in Figure 2. As the radio frequency carrier, the electronic tag and the reader realize the spatial (contactless) coupling of the radio frequency signal through the coupling element. In the coupling channel, the energy transmission and data exchange are realized according to the timing relationship.Discussion on reading rate of RFID systemThrough the introduction of RFID system, we believe that the main reasons for the low reading rate of RFID system are: there are blind areas in the reading range of readers, redundant data in different reading points, mutual interference of readers, etc. In view of the above problems, we discuss them from the following four aspects.
4.1 reasonably optimize hardware configurationIn terms of hardware, we must first clarify a problem. That's what you really need. Don't blindly think that "the price is expensive, the larger the reading range and the higher the frequency, the better". It is the so-called "tailor-made" that "what suits you" is the best. Based on this understanding, you can choose hardware devices that meet the actual needs.
At the same time, consider all RFID tags and readers as a complete "data network", so as to reasonably optimize the hardware configuration, so as to maximize the efficiency of the whole system. Taking the access control system as an example, in order to prevent the blind area in the reading range of the reader, resulting in missing reading, the number of readers or antennas can be increased to compensate for the defect of blind area in the reading range of the reader; In order to prevent mutual interference between readers, the method of relatively isolating readers or antennas in space can be adopted to avoid mutual interference. In addition, according to the actual needs, the data reading rate of RFID system can also be improved by properly adjusting the antenna layout and antenna transmission power.
4.2 improve software designAt present, the hardware facilities of the optimized RFID system can basically meet the needs of data reading rate. With the decline of reader price, end users can easily deploy a large number of readers in their application sites, which not only solves the problem of missing reading, but also obtains more useful information from these systems. But the new problem is: redundant data reading or cross data reading. A simple description of this problem is that "a tag that should not be read in a certain position is read by a reader that should not read this tag".The core of LV positioning logic is based on "picking out the required readout data from the spatial location and filtering out the unnecessary readout data". The result is that the correct and accurate tag position is extracted from the results obtained by all RFID readers. In short, LV positioning logic is a software algorithm based on eliminating "redundant" readout data according to the data set resident in the whole reader system. Colorwave algorithm gives a good solution to the conflict between multiple readers due to overlapping work ranges.
For electronic tag collision, in the high frequency band, the classical ALOHA protocol is generally used as the tag anti-collision algorithm. The tag of ALOHA protocol is used to avoid conflict by selecting the method of transmitting information to the reader after a random time; In UHF band, tree bifurcation algorithm is mainly used to avoid conflict. In addition, other optimization settings can be made for the software. For example, in the e-ticket system, the scanning time interval of the reader can be designed by software to adaptively adjust the scanning time. In case of large traffic, the scanning frequency of the reader can be accelerated through software control to prevent missing reading; In the case of less traffic, the scanning frequency can be relatively reduced, so as to avoid the emergence of redundant data.
4.3 play the role of MiddlewareRFID middleware is the nerve center in various RFID industrial applications. RFID middleware is a message oriented middleware (MOM). Information is transmitted from one program to another or more programs in the form of messages. RFID middleware plays an intermediary role between RFID tags and applications. From the application side, it uses a set of general application program interfaces (APIs) provided by the middleware, that is, it can connect to the reader and read tag data.Therefore, even if the database software or back-end application program storing RFID tag information is added or replaced by other software, or even the type of RFID reader is increased, the application end does not need to be modified. This not only effectively solves the problem of data reading rate, but also saves other problems such as the maintenance complexity of many to many connections. RFID middleware will have very good development prospects in service-oriented architecture (SOA) and business information security applications in the future.
4.4 integration of other technologiesIntegration with sensor technologyIn the next few years, an important application trend of RFID is the equipment that combines RFID with sensors (such as sensors for measuring temperature and pressure). At present, it has been implemented abroad. Because RFID has poor anti-interference and the effective distance is generally less than 10m, its application is limited. Combining WSN (Wireless Sensor Network) with RFID and using the effective radius of the former up to 100m to form wsid network will greatly make up for the shortcomings of RFID system itself.
Integration with WiMAX, 3G, GPS and other communication technologiesWiMax (global interoperability for microwave access) is simply defined as a wireless broadband data transmission system. The wireless service range of WiMAX can be as far as several kilometers under the condition of maintaining high data traffic in urban areas. Its performance far exceeds the existing wireless network technology. In directional communication connection, the service range can reach 50 km under the condition of maintaining certain data traffic. Due to its extremely high performance, WiMAX technology is considered to be the best backup scheme for DSL UMTS connection.
The integration of WiMAX, 3G, GPS and RFID is moving forward with the active participation of all parties. RFID tag has the characteristics of small volume, large capacity, long service life and reusable. It can support fast reading and writing, non visual identification, mobile identification, multi-target identification, positioning and long-term tracking management. The cost saving and efficiency improvement promote RFID technology to become an important entry point for various industries to realize informatization. They will build a wireless broadband network that can meet the needs of a variety of application environments and generate rich applications, expanding the application field of RFID technology.
Fusion with biometricsBiometric recognition technology is a solution to complete authentication by using automatic technology to measure their physical characteristics or personal behavior characteristics, and comparing these characteristics with the template data in the database. The biometric recognition system captures the samples of biometrics, and the unique features will be extracted and transformed into digital symbols, which are stored as personal feature templates. People interact with the identification system to authenticate their identity to determine whether they match or do not match. At present, the commonly used biometric recognition technologies include fingerprint, palmprint, face, voice, retina, signature recognition and so on.In short, the integration of RFID system with other technologies is imperative, and great achievements have been made. It solves the problem of low data reading rate of RFID system, which will inevitably make RFID technology widely used. Finally, it will go deep as bar code technology and slowly extend to all aspects of various industries, which plays a key role in improving operation efficiency and economic benefits of the industry, so as to promote a new leap in the global economy and have a far-reaching impact on human society.
5 Conclusion
On the whole, the development of RFID system will be better and better in the future. Although there are still some technical and application problems such as low reading rate, we believe that it is not difficult to overcome the current problems of RFID through a series of measures such as optimizing hardware configuration, improving software design, playing the role of middleware and integrating other technologies. Under the strong market orientation, RFID technology will cause a major change all over the world. It will become a new economic growth point in the future, and will eventually become the largest information technology support for the development direction of Chinese enterprises. It can be predicted that in the near future, as a global manufacturing base, China will be the world's largest RFID application market in the future. This will be a rare opportunity for domestic scientific research institutions and enterprises.
4
Standard Regulations and Best Selection Scheme of AC / DC Power Supply in Medical Equipment
Power supply standardIEC -1: and accompanying documents specify the safety and basic functional requirements of the power supply. The standard appears in the form of ANSI / AAMI document in the United States and in the form of "euronorm" in Europe and around the world, with some local differences. Since January , the latest revision (a1:, a2:) has updated the standard, deleted outdated references, corrected errors and made it better consistent with IEC -1. The current medical EMC standard IEC -2 is the 4th Edition.Built in medical power standard
AC powered medical devices can have "built-in" power supplies or lower power external adapters. If it is an internal product, the product designer should consider high voltage and high energy, and usually choose to buy a "medically certified" power supply. However, the final product is the product certified for this application, so there are other considerations, such as labels, connectors, internal wiring of power supply and fuses.
Due to grounding, external wiring and interference from other noise sources, the built-in power supply conforming to EMC standards cannot be guaranteed to pass the test. A common practice is to add another EMI filter at the AC inlet, which may be included in the connector. However, it should be noted that the leakage current limit should not be exceeded. For the most stringent CF product rating, the leakage current limit can be as low as 10 a. The leakage of external filter may directly lead to the internal leakage of AC power supply, there is a risk of interaction between external filter and internal filter, and may even worsen EMI.
Secure power solutionsThe safe solution should select the target application and specify a power supply with 2 x MOPP certification and EMC compatible performance. For example, power supplies from recom racm230-g, racm550-g and the recently released racm-v series.Their peak or rated power is 230W, 550W and W respectively. When fans are not allowed (usually in medical environments), these products can be floor cooled. All products have 2x MOPP / 250V AC rating to prevent leakage to ground (racm550 / ). The safety barrier in each recom power supply is shown in Figure 2.
Figure 2: safety fence racm230 / 550 / seriesFigure 3: a 2x MOPP DC / DC converter provides SIP / SOP isolationUsing a medically certified power supply (such as the power supply of recom) is a reliable way to ensure that the safety and EMC standards required by various medical application environments are met. It would be a lower overall cost approach if development, certification costs and time to market were taken into account.
Recom is a good choice when selecting AC / DC power supply for medical equipment. Eurotime electronics, as a distribution partner of recom, provides local inventory and technical support.Original title: eurotime classroom | AC / DC power supply in medical applicationsThe source of the article: WeChat official account: Euro time electronic RS] welcome to add attention! Please indicate the source of the article.
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5
Application of Hongke PCA in Medical Equipment Industry
This series of articles introduces the application solutions of Hongke PCA in the medical equipment industry, including life science instruments, CT medical equipment, centralized control system and so on.
Application of PCAN interface card based on Hongke in hemodialysis machine
The number of patients with end-stage renal disease in China is huge and increasing year by year. Hemodialysis is a relatively mature alternative therapy, which can alleviate patients' symptoms and prolong patients' life. At present, China's hemodialysis machine market is mainly occupied by imported brands. The research and development of domestic hemodialysis machines with high quality and low price is not only the pursuit of China's medical enterprises, but also of great significance to the progress of science and technology and the development of medical undertakings.
Hemodialysis is to drain the blood in the body to the outside of the body through a dialyzer composed of countless hollow fibers. The blood and electrolyte solution (dialysate) with similar body concentration are inside and outside the hollow fibers, and exchange substances through dispersion / convection to remove metabolic waste in the body, maintain electrolyte and acid-base balance, and remove excessive water in the body.
Challenge
Shortcomings of traditional hemodialysis machine
In the actual treatment in the hospital, different modules need to be selected for treatment according to the situation of patients. After years of development, the function, safety performance and humanized design of domestic advanced models are comparable to those of foreign models, but domestic hemodialysis machines still have shortcomings. For example, most hemodialysis equipment does not have the functions of blood volume monitor, multiple sets of independent CPU systems and central networking. Although it has a variety of safety monitoring functions, the actual failure rate is high. Whether it is the appearance of the equipment, the principle of the hydraulic system of the machine, the design of parts, etc., there is a lack of innovation and lack of core competitiveness.
programme
Application and optimization of PCAN interface card based on Hongke in hemodialysis machine
In order to optimize the original prototype according to the new requirements and higher requirements, it is necessary to consider the system integrity, safety, accuracy and so on. Based on the above problems, Hongke PCA interface can be used to further R & D and optimization of hemodialysis machine.
Hemodialysis machine has many electronic control parts, which has high requirements for various indicators in the work of the machine. It needs an efficient and stable automatic control system to make dialysis run safely. Therefore, the control system of hemodialysis machine should meet the basic requirements of automatic control system, that is, stability, rapidity and accuracy.
For the control system of hemodialysis machine, its safety includes not only the control system itself, but also the executive parts controlled by the control system. When the control system has its own security, it should know the operation of the executive parts. When the actuator fails or does not work normally occasionally, the control system should be able to infer what parts have failed, what faults have occurred, what causes the faults and how to deal with them from the feedback of its components or according to the overall operation of the system.
Therefore, the functions of the control system structure of hemodialysis machine include: collecting the signals of various sensors to ensure the safety of dialysis; Control the movement of each pump to achieve accurate control of important parameters and meet the standard.
The control system of Hongke scheme can be divided into upper layer and lower layer. The upper layer is the main controller of upper computer and lower computer, and the lower layer is the motor and its driver, sensor module and three solenoid valve control boards. Its hardware structure is shown in the figure. The control system mainly includes the upper controller, the lower executive components and sensor modules. The upper computer is responsible for human-computer interaction function, obtaining medical staff instructions, displaying treatment parameters, etc. the main controller of the lower computer receives the instructions of the upper computer, completes the functions of the hemodialysis machine, and uploads the parameters to the upper computer. The motor, driver and solenoid valve are the executive components, The sensor acts as an information feedback component.
According to the requirements of the control system, the functions of each hardware module are divided as follows:
1) The host computer mainly realizes the human-computer interaction function, including guiding medical staff to carry out dialysis operation, displaying dialysis parameters in real time, providing maintenance personnel with maintenance platform, etc. The upper computer communicates with the main controller of the lower computer through CAN bus.
2) The main controller of the lower computer is used to realize the overall control of the hemodialysis machine, that is, collect sensor information such as temperature, conductivity and flow, control motors such as blood pump, degassing pump and flow pump, and control the drive of solenoid valve controller.
3) The motor and driver are the actuator of the control system, and the sensor module is the information acquisition device.
4) The solenoid valve controller is responsible for driving the solenoid valve and feeding back the status of the solenoid valve.
In this communication process, the can communication task is mainly responsible for the communication of devices on the CAN bus. We can give the highest priority to communication tasks to ensure that the control commands and parameters of the upper computer can be transmitted to the lower computer in time at any time. All communication between the upper computer and the lower computer is completed by this task, and other tasks can only contact the upper computer indirectly through this task. In the can receiving interrupt, it receives the data sent by the upper computer, caches the data, and triggers the can communication task by sending semaphore for analysis and execution.
HONGKE
Key characteristics of Hongke PCA interface card
high speed USB 2.0 adapter (compatible with USB 1.1 and USB 3.0)
two D-sub connectors are used to send and receive can FD and Lin messages (both are allocated by pins of can FD and LIN bus)
comply with can specification 2.0 A / B and FD
each can FD channel shall separate USB and Lin, with a maximum of 500V
can terminal can be excited by welding jumper
bus load measurement includes error frame and overload frame
induce error to generate can message for input and output
summary
The application and optimization of Hongke PCAN interface card in hemodialysis machine can meet the requirements of product stability, rapidity and accuracy. It can also be used with our handheld tester PCAN diag FD for various fault diagnosis, such as various fault diagnosis by processing CAN2.0 and can FD messages in the protocol layer, and oscilloscope function and voltage in the physical layer Resistance measurement function for fault diagnosis. At present, many manufacturers at home and abroad have used PCA interface card to upgrade their medical equipment. If you want to know more about PCA interface card, please contact Hongke for product information and trial opportunities.
Original title: [PCA medical application series] part6 application in hemodialysis machine based on Hongke PCA interface card
The source of the article: [WeChat official account: Guangzhou Rainbow Electronics Technology Co., Ltd.] welcome to add attention!