C8051F series MCU based glucose meter solution (1)

Blood glucose measurement principle of the electrochemical

Blood glucose measurement principle for electro-Biochemistry is imposed certain voltage to the enzyme reaction of blood resulting current as the blood glucose concentration in the blood increases.

By accurately measuring out these weak current, and according to the current value and the relationship between blood glucose concentration, figure out the appropriate concentration. Therefore, to determine the relationship is the core of the problem. But their relationship is complex and influenced by many factors. Voltage intensity, the use of the discussion and the detection of blood volume will have an impact on it. In theory, you need all the concentration point on a large number of experiments to determine the final relationship. In practice, simply select the number of significant concentration points do a large number of experiments, and then uses the curves or interpolative, data processing methods to determine its current value.

Blood glucose measurement is typically used in electrochemical analysis for three-electrode system.

Three-electrode system is relative to the traditional two-electrode system, including working electrode (WE), reference electrode (RE) and on the electrode (CE). Reference electrode used to point-zero, the current flowing through the work of electrode and electrode working electrode and reference electrode forming a barrier or basic little power system, using reference electrode potentials of stability to measure working electrode electrode potential. Working electrode and auxiliary electrode forming a power system that is used to measure the current working electrode through. Use three-electrode measurement system, to examine the working electrode sites and current relationship. As shown in Figure 1.

Figure 1 three-electrode working principle

Programme description

The blood glucose meter provides multiple operating modes to suit different occasions, also provides mmol/L to mg/dl, g/l three common units of measure of freedom to switch and automatic conversion.

The three units conversion as follows:

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

In view of the different requirements of different countries and regions, blood glucose meters can be used over any of the units to display measurement results, the conversion of code taken use special calibrations section.

(1) internal MCU and full utilization of hardware resources.

Silicon labs C8051F410 MCU internal integrates rich peripheral simulation device that allows users to take full advantage of its rich hardware resources. C8051F410 MCU logic function diagram shown in Figure 2. Use 12-bit A/D converters used to make small signal measurement, small signal current after current sampling circuit eventually convert to voltage from the A/D sampling, and then to the established conversion program to calculate the concentration is displayed in the LCD Panel. Use 12-bit D/A converter can output accurate and stable reference voltage for the three-electrode measurement process, because the D/A output can be changed by any of the programming, so you can very easily by changing the value of D/A to change the reference voltage and voltage differential pressure between, and 12-bit precision ensure a pressure differential of stability, improve measurement accuracy.

Figure 2 C8051F410 logic function diagram

Temperature sensor for temperature signal acquisition, temperature compensation [4].

Because glucose reagents in temperature too high or too low measurement deviation will appear, so the measurement process by the temperature sensor acquisition environment temperature, the temperature of the reagent requirements outside of the parameters can be used as a temperature compensation.