A glucose meter (or glucometer) is a medical device used to determine the concentration of glucose in the blood. A small drop of blood, obtained by pricking the skin with a lancet, is placed on a disposable test strip that the meter reads and uses to calculate the blood glucose level. The two types of glucometers are electrochemical based and optical reflection based.
Electrochemical-based glucometers are the most popular type, Figure 5. Electrochemical test strips have electrodes where a precise bias voltage is applied with a digital-to-analog converter and a current proportional to the glucose in the blood is measured as a result of the electrochemical reaction on the test strip.
There can be one or more channels, and the current is usually converted to a voltage by a trans-impedance amplifier for measurement with an analog-to-digital converter. The chemical strips have to be used externally and temperature correction has to be implemented for accurate measurement.
Figure 5: Block diagram of glucose monitor
Respiratory rate is measured using a device known as a spirometer which measures the volume and speed of air that is inhaled and exhaled by the lungs. A spirometer provides a first-level diagnostic test for some pulmonary diseases.
Spirometers typically use turbine transducers or pressure sensors to measure the respiratory measurement, Figure 6. Turbine encoders measure the rate of flow based on the number of rotations which in-turn depends on the airflow rate and volume.
Figure 6: Blo