Impedance Measurement Blood Analysis Systems

Blood analysis can be performed in several ways, using technologies that include impedance measurement and flow cytometry. Although each type of design has unique requirements and challenges, both depend on accurate, reliable, repeatable data acquisition and analysis. In addition, high speed and wide bandwidth are critical. Both flow cytometry and impedance measurement system designs typically consist of a stimulus generator, a data acquisition system, an application processor, and a wide range of products that address the needs of each of these elements.

Impedance Measurement Systems

An impedance measurement system provides accurate and fast analysis of constituent components of liquids and samples. A user-selectable frequency stimulus signal is applied through the sample and the impedance changes, based on changes induced in the sample. Examination of the resulting impedance signature is indicative of what is being analyzed. For example, when a known strain of a virus is added to a blood sample, an antigen response takes place, producing a chemical reaction that can alter the impedance of the blood. By characterizing this effect across different frequencies, it is possible to detect a specific strain of virus.


The AD5933 is a flexible single chip impedance converter capable of generating different excitation frequencies and examining the resulting impedance spectrum. It features a 100 Ω to 10 Ma impedance measurement range, programmable excitation up to 100 kHz with 0.1 Hz resolution, and data output as real and imaginary allowing impedance phase and magnitude to be calculated at each frequency point. The AD5934 has the same impedance measurement range as the AD5933, but it has a 250 KSPS sampling ADC, as opposed to the 1 MSPS sampling ADC on the AD5933. The AD5934 does not include the on-board temperature sensor. Both the AD5933 and AD5934 are available in a 16-lead SSOP.

The ADuC7021 precision analog microcontroller is a fully integrated data acquisition system-on-a-chip, featuring an ARM7TDMI® MCU core and 12-bit, 1 MSPS ADC. It features precision analog-to-digital and digital-to-analog conversion and a flash microcontroller. The ADuC7021 is available in a 40-lead LFCSP.