Guide to Buy Medical Bed Delivery in
medical bed delivery is a valuable product with high cost-performance ratio. With regard to raw materials selection, we carefully select the materials with high quality and favorable price offered by our reliable partners. During the production process, our professional staff concentrate on production to achieve zero defects. And, it will go through quality tests performed by our QC team before launched to the market.
Manufactured from superior materials with modern technology, medical equipment manufacturer is highly recommended. It is tested on the international standards instead of the national rules. The design has always been following the concept of striving for first-rate. The experienced design team can better help to meet customized needs. Client's specific logo and design are accepted.
Professional and helpful customer service can also help win customer loyalty. At qtjadx3f, customer's question will be responded rapidly. Besides, if our existing products like medical bed delivery do not meet needs, we also provide customization service.
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1
Discussion on the Technology 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 population aging problem, the above demand is more urgent
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 lmp7731, 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 lmp7731.
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 lmp7731 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 lmp7731 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.
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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 lmp7731, 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 lmp7731.
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 lmp7731 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 lmp7731 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.
2
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, J1939, 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.
![]()
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, J1939, 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
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 2011.
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 lmp7731, 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 lmp7731.
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 lmp7731 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 lmp7731 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 = 0.007813 * f-3db is obtained in this example. For the operational amplifier (LMP7711) 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 0.007813 * 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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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 lmp7731, 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 lmp7731.
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 lmp7731 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 lmp7731 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 = 0.007813 * f-3db is obtained in this example. For the operational amplifier (LMP7711) 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 0.007813 * 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.
4
Standard Regulations and Best Selection Scheme of AC / DC Power Supply in Medical Equipment
Power supply standardIEC 60601-1:2005 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 2021, the latest revision (a1:2012, a2:2020) has updated the standard, deleted outdated references, corrected errors and made it better consistent with IEC 62368-1. The current medical EMC standard IEC 60601-2 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-1200v series.Their peak or rated power is 230W, 550W and 1200W 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 / 1200). The safety barrier in each recom power supply is shown in Figure 2.
Figure 2: safety fence racm230 / 550 / 1200 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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