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The topic of “impedance” or “impedance spectroscopy” has become increasingly important in recent years, especially in the field of batteries. First of all, the term impedance only refers to a complex AC resistance and is therefore not a new topic. Nevertheless, the analysis of AC resistance is a significant methodology, especially for electrochemical systems and for material studies.
Pure impedance analysers
Pure impedance analysers, such a PSM-Serie von Newton’s 4th, are characterised by very high measurement accuracy. They are specialised laboratory instruments for particularly precise measurements. The bandwidth ranges from the PSM1700 with a maximum frequency of 1 MHz, to the PSM1735 (max. 35 MHz) to the PSM3750 (up to 50 MHz). The typical applications of these devices are mainly in the development of circuits and components or in the audio field. Nevertheless, the PSMs can also be used for electrochemical analysis, especially for material analysis, in order to benefit from the high-precision measurement technology.
Potentiostat-integrated impedance analysers
Potentiostat-integrated impedance analysers are primarily oriented towards the needs of electrochemical measurements. Smaller frequency ranges are covered and the current and voltage amplitudes correspond to the measuring ranges of the potentiostat. However, the perfect combination of potentiostatic or galvanostatic measurement with impedance spectroscopy is advantageous. The low accuracy can be tolerated, since real electrochemical systems are anyway subjected to strong disturbances, especially in high frequency ranges. Since almost all potentiostats/galvanostats have an impedance function, the choice is wide. The PalmSens EmStat4S is clearly the most affordable option for electrochemical impedance spectroscopy. For mobile use or field measurements, the PalmSens4 or the Ivium pocketStat2 are ideal due to their compact dimensions and (optional) battery and Bluetooth operation. For more demanding applications, in terms of accuracy and frequency range, the die Ivium-Potentiostate CompactStat und IviumStat are reliable instruments: at a maximum of 3 and 8 MHz respectively and with 24-bit analogue/digital conversion, the most accurate measurements in the field of potentiostat impedance analysers are possible.
Multichannel instruments by Ivium and MaterialsMates
Multi-channel devices OctoStat and IviCycle by Ivium occupy a special position. Designed as multi-channel potentiostats, these devices are primarily aimed at battery measurements. An important feature is the integration of parallel impedance measurement for all channels without or only with very low additional costs.
Especially in the field of electrochemical energy storage and conversion, there are application scenarios that require a high number of parallel EIS measurements. For example, for investigations on fuel cell or electrolysis stacks, it is of great importance to screen the individual cells in parallel/simultaneously. Depending on the stack size, there are various options. For short stacks of up to eight cells, the Ivium Stackanalyzer is a cost-effective solution as an extension to an Ivium potentiostat with EIS. For larger stacks or applications with a high number of simultaneous EIS measurements, a multi-channel EIS system by MaterialsMates is perfectly suited. Design and specifications are fully customisable.