What is electrical impedance?
Electrical impedance is the measure of opposition a circuit presents to a current when a voltage is applied. Impedance extends the concept of resistance to AC (Alternating Current) circuits and possesses both magnitude and phase, unlike resistance, which has only magnitude. When a circuit is driven with DC (Direct Current), it makes no distinction between impedance and resistance; the latter can be thought of as impedance with a phase angle of zero. (From Wikipedia)
What is bioimpedance?
The term electrical bioimpedance (or simply bioimpedance) refers to the passive electrical properties of biological tissue, determined by their response to the injection of external excitation current or applied excitation voltage. Tissue consists of cells and membranes. Thin but highly resistive membranes behave electrically as small capacitors. By using high measuring frequencies, the current passes right through these capacitors, and the result depends on the tissue and liquids both inside and outside the cells. At low frequencies, however, the membranes impede current flow, and the results depend only on the liquids outside the cells. (From UIO Department of Physics).
What is impedance spectroscopy?
Impedance spectroscopy, a widely recognised method, examines the properties of various materials and objects in engineering, industry and biomedicine. In most applications, the impedance data is used for mapping and correlation with a phenomenon of interest. Relative by nature, the measurement focuses on a change or comparison with a baseline, rather than determining the value of impedance on an absolute scale.
Which use cases does it best suit?
We see many companies and research groups develop innovative products based on impedance measurement—now widely used in many scientific and technical fields. For example, applications can be found in biomedicine, robotics, material science, the food industry and energetics to name a few.
In general, applications where the measurement time is limited or the phenomenon of interest is changing rapidly best suit impedance spectroscopy. The high repeatability of the measurement and a sufficient number of frequency points on the spectrogram facilitate the accurate characterisation of objects or systems under investigation.
Does Eliko offer electrodes for impedance measurements?
Eliko does not offer standard impedance measurement electrodes, mainly because of the unique use case of each impedance measurement and the potential insufficiency of standard electrodes. However, we can offer our know-how in the design and production of custom electrodes in cooperation with our partners. That way, you can be sure that the electrodes meet their requirements.
What is the Quadra impedance analyser?
Real time electrical impedance spectroscopy device Quadra expertly measures a spectrogram of 15 frequencies with a speed of 1000 measurements per second. The compact enclosure includes all the circuitry required to generate a spectrally sparse excitation voltage and measure the response voltage and current.
The Quadra impedance analyser can be used as a standalone measurement device for experimenting, but at the same time the technology is suitable for embedding in OEM devices.
Elements of the Quadra platform
The Quadra impedance spectroscopy platform consists of an application specific front-end and the DSP (Digital Signal Processing) module, which streams measured data to the host system for further processing. The platform can be implemented as modules—in separate enclosure(s) or integrated into the host system enclosure. The front-end and DSP circuits can also be embedded in a custom PCB design.
What kind of front-ends are available?
Please see the Product Sheet for a list of available front-end designs.
Does it perform impedance spectroscopy in real time?
Yes, Quadra provides real-time impedance spectroscopy in a compact form, well-suited for embedding or autonomous field applications.
What is the spectrogram acquisition period?
The spectrogram acquisition period depends on the selected frequency range. For example, by selecting the highest frequency range (1 to 349 kHz) the acquisition period is 1 ms.
What is the spectrogram frequency range?
Different sets of 15 frequencies can be selected. The highest set, 1 kHz to 349 kHz, enables a 1 ms acquisition time and covers a wide range of applications from tissue and material structure mapping to the detection of cells and coatings. The lowest set, 0.5 Hz to 195 Hz (acquisition time 2 ms), extends down to frequencies used for electrochemical applications.
What powering options does Quadra have?
USB bus: 500 mA (2.5 VA), or internal battery (8 h autonomous operation).
What does the Quadra evaluation kit include?
The Quadra evaluation kit includes:
- Quadra DSP module;
- Single shunt front-end with voltage excitation and 1 kΩ current measurement shunt;
- Software (Windows GUI; LabVIEW and matlab toolboxes) for operating Quadra as well as data acquisition and visualisation;
- Impedance demo board for setup verification.
What are the module dimensions?
(110 × 60 × 20) mm, (140 x 60 x 20) mm with a front-end.
How much space does DSP module embedding require?
DSP module embedding requires less than (30 × 30) mm of PCB area.
What is the accuracy of Quadra?
The accuracy of the system is up to 0.1 %, but it depends on the measurement and frequency range. (0.1 % of the measured value represents the repeatability error of the Quadra.)
What does the software include?
The Quadra Control Panel, a graphical user interface (GUI), uses Windows operating system. It enables configuration of the system and real-time visualisation of the measurement results. The software package also includes LabVIEW and MATLAB toolboxes with similar functionalities.