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Detailed explanation of the principle design and imitation development plan of blood glucose meter

Date: 2018-03-27
Viewed: 74
案例名称: Detailed explanation of the principle design and imitation development plan of blood glucose meter

Blood glucose measurements typically employ a three-electrode system in electrochemical analysis. The three-electrode system is relative to a conventional two-electrode system, including a working electrode (WE), a reference electrode (RE), and a counter electrode.

(CE). The reference electrode is used to fix the zero point, the current flows through the working electrode and the counter electrode working electrode and the reference electrode form a system with no or substantially less energization, and the electrode potential of the working electrode is measured by the stability of the reference electrode potential. The working and auxiliary electrodes form an energized system for measuring the current through the working electrode. A three-electrode measurement system was used to simultaneously study the relationship between the point and current of the working electrode. Figure 1 Shown.


Figure 1 Three-electrode working principle

Program description

The blood glucose meter provides a variety of operating modes to suit different applications, and provides free switching and automatic conversion of three common measurement units: mmol/L, mg/dl, and g/l. The conversion relationship between the three units is as follows:

1mmol/L=18 mg/dL 1mmol/L=0.18 g/L 1 mg/dL=0.01 g/L

  For different requirements in different countries and regions, the blood glucose meter can display the measurement results in any of the above units, and the conversion method is implemented by using a special code correction strip.

  (1) Full utilization of the microcontroller and internal hardware resources. Silicon labs

The C8051F410 microcontroller integrates a wealth of peripheral analog devices, allowing users to take full advantage of their rich hardware resources. The logic function diagram of C8051F410 microcontroller is shown in Figure 2. A 12-bit A/D converter is used for small signal measurement, and the small signal current is finally converted into a voltage by the current sampling circuit and sampled by the A/D, and then the concentration is calculated and displayed on the liquid crystal panel by a predetermined conversion procedure. The 12-bit D/A converter can be used to output a precise and stable reference voltage for the three-electrode electrochemical measurement process. Since the D/A output can be arbitrarily changed by program programming, it is convenient to change the D/A value. To change the voltage difference between the reference voltage and the working voltage, and the 12-bit precision can ensure the stability of the differential pressure and effectively improve the measurement accuracy.


Figure 2 C8051F410 logic function diagram

  The temperature sensor is used to collect the temperature signal and make temperature compensation [4]. Because the blood glucose reagent has a problem of measurement deviation when the temperature is too high or too low, the ambient temperature is collected by the temperature sensor during the measurement process, and the parameter can be used as temperature compensation outside the temperature range required by the reagent. .

An internal 32/16kB flash memory can be used to store measurement data. 2kB of integrated RAM is used as a buffer for measurement data. The blood glucose meter needs to record each measurement data and date in a non-volatile storage medium, usually using a flash memory, but the flash memory generally has a problem of slow rewriting speed. Therefore, using the 2kB RAM as a buffer, there is a power supply. In the case of recording data, the data is written into the Flash every time the blood glucose meter is turned off, which indirectly improves the measurement efficiency of the blood glucose meter.

(2) The power supply design uses two ordinary alkaline AAA batteries, which use RT9701 and RT9266 to form a high-efficiency boost circuit to boost to 3.3V as the power supply for the whole blood glucose meter. Design the power switch circuit on the power supply circuit structure of the whole instrument, except when shutting down

The MCU and the real-time clock can be directly powered by the battery. The power of other circuits is completely cut off, and then the MCU and the real-time clock are put into a sleep or power-saving state, which can greatly save standby power consumption and prolong battery life. The wake-up of the MCU is realized by an interrupt. When the switch button is pressed, a button interrupt is generated, thereby awakening the MCU and turning on the power for other circuits, and the blood glucose meter is re-entered.

(3) Real-time clock design, using s-3530A real-time clock chip [5]. The real-time clock has the characteristics of high precision and low power consumption. The working crystal frequency is 32K, and it has a power-saving mode, which can enter the power-saving mode when the blood glucose meter is not working, saving battery power. The I2C bus is used to connect with the MCU, which effectively saves the I/O port line of the MCU. The leap year is automatically calculated, and the year, month, and day time data is expressed in BCD code format, which provides great convenience for MCU reading and writing.

(4) Different user mode design. The end customer only needs to record the history of blood glucose testing and testing, and the debugging personnel need to know the measured current value to detect the quality of the instrument. Therefore, the program deliberately designs two operating modes for the end user and the debugging during the production process. For personnel use, it is only necessary to use a special test strip to make the instrument into super user mode. This mode provides a display interface for test current. Under this interface, the debugger can test the instrument with a standard resistor instead of a reagent. Performance. The general end user can only use it in the normal user mode, so that the production test and the final sale of the instrument can use the same program, which brings great convenience to the production and brings convenience for the maintenance of the product.

(5) Code correction of the blood glucose meter. The blood glucose meter needs to perform code correction without replacing a batch of reagents. The so-called code correction is actually inputting a new set of fitting curve parameters to the blood glucose meter. This parameter will be pre-programmed on the code correction bar, and the correction code bar is as image 3. The feature code is actually the integration of the parameters of the fitted curve into a special code form. Figure 4 is a reagent strip, which is prepared by a professional biomedical organization. Because the dispensing of each batch of reagent strips is not possible, the parameters of the fitting curve are different each time. This parameter is provided by the mechanism and the corresponding calibration code is programmed. The strip is delivered to the end user with the reagent. Each time a user purchases a new batch of reagents, the parameters of the meter must be modified by a code correction strip. The code correction strip is designed to have the same interface as the reagent strip, so it is only necessary to insert the new parameters into the meter by directly inserting the meter's detection port like a reagent strip.


图3 校正代码条


Figure 4 reagent

  (6) Based on the requirements of the previous point, the port of the blood glucose meter must be able to read the reagent strip correctly and read the calibration code strip, so the port is a composite port of two functions. Therefore, an ingenious circuit conversion structure is designed on the circuit for automatically determining whether the reagent strip or the code correction strip is correctly read according to the inserted medium.

(7) Design of special code correction bars. Since this scheme is designed with automatic conversion of units, general user mode and super user mode, the implementation of these functions relies on special code correction bars. The principle is to select several special codes, burn them in the code correction bar, and use blood sugar. The instrument can automatically read the code correction bar to set the function of the parameter. When reading the code, it first judges whether it is a special code. If it is, it performs the corresponding operation, otherwise it enters the new parameter setting, as shown in Figure 7. The special code includes the following contents, the code of the conversion unit, the code for switching the working mode, the code for clearing the memory, and the like.

Circuit implementation and man-machine interface

The structure of the blood glucose meter is shown in Figure 5. The blood glucose meter uses a PDM1621-893 custom LCD module as a human-machine interface. The module can realize various displays such as real-time clock, battery power, measurement unit, alarm signal, code prompt, etc., combined with three-digit seven-segment digital display. Programming can provide as much information as possible in multiple work modes. The structure of the liquid crystal panel is shown in Figure 6. The operation process of the whole blood glucose meter is shown in Figure 7.


Figure 5 circuit structure


Figure 6 LCD panel structure


Figure 7 program flow

As a medical electronic instrument commonly used in clinical medicine, blood glucose meter is mainly used for clinical diagnosis by measuring blood glucose concentration in blood. Century Core has many years of service experience in the field of imitation development, maintenance and repair of various medical electronic instruments and high-end expensive medical equipment. It can provide a complete set of technology for replacement and repair of medical equipment circuit boards, troubleshooting, circuit board copying, prototype cloning, and debugging production. The service can also provide the extraction and transfer of a complete set of technical data of many medical electronic devices such as blood glucose meters according to customer needs, assist product development and application users to carry out maintenance and improvement and upgrade, or assist engineers in product reference design.

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