![]() ![]() For a list of Analog's recommended glucose-meter solutions, please go to: BGM (Blood Glucose Meter) Solutions Glucose Meter Solutions Accuracy and Precisionīoth optical-reflectometry and electrochemical meters need to resolve currents in the single-digit nano-amp range. A pack of test strips inside the meter also facilitates testing because these often small strips do not need to be handled and inserted by the user.įunctional block diagram of a blood glucose meter. This "self-calibration" can be accomplished three ways: with tight manufacturing controls, built-in calibration on each test strip, or built-in calibration on a pack of test strips loaded into the meter. Some meters use test strips that do not require any coding by the user. ![]() A 1-Wire ® memory device provides an additional benefit, because the unique serial identification number in each 1-Wire device ensures that the proper test strip is used. An EPROM or EEPROM memory device enables additional information to be transferred, which is a significant advantage over manually entering a code. Calibration is done by entering a code manually or by inserting a memory device from the package of test strips. The test strips usually need to be calibrated to the meter to account for manufacturing variations in the test strips. Optical-reflectometry blood glucose meter. Ambient temperature is required for this method. The full-scale current from the photodiode ranges from 1♚ to 5♚ with a resolution of less than 5nA. The photodiode current is usually converted to a voltage by a TIA for measurement with an ADC. A photodiode senses the reflectedlight intensity, which is dependent on the color of the test strip, which, in turn, is dependent on the amount of glucose in the blood. Typically, a calibrated current passes through two light-emitting diodes (LEDs) that alternately flash onto the colored test strip. Optical-reflectometry test strips use color to determine the glucose concentration in the blood. Ambient temperature needs to be measured because the test strips are temperature dependent. The full-scale current measurement of the test strip is in the range of 10♚ to 50♚ with a resolution of less than 10nA. There can be one or more channels, and the current is usually converted to a voltage by a transimpedance amplifier (TIA) for measurement with an analog-to-digital converter (ADC). Electrochemical test strips have electrodes where a precise bias voltage is applied with a digital-to-analog converter (DAC), and a current proportional to the glucose in the blood is measured as a result of the electrochemical reaction on the test strip. The majority of blood glucose meters are electrochemical. Single-test meters use electrochemical or optical reflectometry to measure the glucose level in units of mg/dL or mmol/L. Continuous meters are by prescription only and use a subcutaneous electrochemical sensor to measure at a programmed interval. There are continuous and discrete (single-test) meters on the market today, and implantable and noninvasive meters are in development. Other conveniences include speedy results, edge fill strips, and illuminated test strip ports, to name just a few. Accurate and precise results have been increased by using better test strips, electronics, and advanced measurement algorithms. This eliminates the need to obtain blood from the fingers and greatly reduces the pain associated with daily testing. The blood sample size is now small enough that alternate-site testing is possible. Over the past few years the trend with blood glucose meters has been to maximize patient comfort and convenience by reducing the volume of the blood sample required. The mark of a good meter is one that the patient will use regularly and that returns accurate and precise results. Overviewīlood glucose meters and other home medical devices today are small, portable, and easy to use. It explains the different types of calibration used for test-strips, and discusses other variables that designers must consider when selecting products. This tutorial introduces the different types of glucose meters. ![]()
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