A small drop of the solution to be tested, is placed on a disposable test strip, that the glucose meter uses for the glucose measurement.
Glucose meter test strips
The gluconic acid then reacts, with another chemical in the testing strip called ferricyanide. The ferricyanide and the gluconic acid, then combine to create ferrocyanide.
Once ferrocyanide has been created, the device runs an electronic current through the blood sample on the strip.
This current is then able to read, the ferrocyanide and determine how much glucose is in the sample of blood, on the testing strip. That number is then displayed on the screen of the glucose testing meter.
- Colorimetric method and
- Amperometric method.
The Colour Reflectance principle is used in this method to sense the colour intensity in the reaction layer of the test strip by the photometry.
The glucose meter generates a numerical value, that is a measurement of the glucose concentration present in the solution.
In this method, the electrochemical test strip contains a capillary that is used to draw in the solution placed at one end of the test strip. The test strip also contains an enzyme electrode containing a reagent such as Glucose Oxidase.
An ambient temperature measurement is also made in order to compensate for the effect of temperature on the rate of the reaction.
The solution sample (Blood) is placed on the test strip and the reaction of the glucose with the enzyme takes place.The flow of electrons will correspond to the flow of current through the working and the reference electrodes. This current will change according to the glucose concentration.
The current is measured using a transimpedance amplifier (current-to-voltage converter) and an analogue-to-digital converter (ADC). The output of the transimpedance amplifier will be seen as a variation in the voltage with varying glucose concentrations in the solution.
Factors affecting Glucose Measurement
- Altitude, etc.
- Glucose Meter Reference Design, Microchip.
- Glucose Meter Fundamentals and Design, Freescale Semiconductor Inc.
- Other Internet Sources