Test & measurement


Liquid measurements: From water to blood


By Christoph Kämmerer, field applications engineer, Analog Devices T


he determination of the composition and quality of liquids is essential in a wide variety of applications. The most prominent example is water, the most precious raw material in the


world. Clean water and water filter technology play important roles around the world and are necessary to life. Access to continuously declining clean water resources is an increasingly important topic. However, examples of liquid measurements extend far beyond water - fluids in medicine such as blood, saliva, and faecal matter must be able to be tested for possible diseases because they have a direct impact on


health. What all these measurements have in common is the underlying measurement principle - an impedance measurement. In this article, we will concentrate on fluid measurements with medical uses and thereby describe the individual applications as well as the versatility of impedance measurements.


FluiD MeAsureMents in MeDiCine The most widely known fluid measurement in medicine is blood glucose measurement. Here, a drop of blood on a test strip is sufficient for drawing conclusions about the blood sugar level in the blood. Based on this value, the


Figure 1. Measurement principle for a potentiostat measurement.


Figure 2. Amperometric measurement.


42 January 2022 Instrumentation Monthly


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