18th September 2025

Electrochemical Impedance Spectroscopy

Do you require a power system to analyse the electrochemical properties of your energy storage device? Maybe you need to characterise switches at high speeds? Perhaps your existing PSU isn’t dynamic enough to cope with your component’s transient response demands? Our DC systems could be the catalyst your testing needs...

The G5 series allows users to program a current ripple up to 10kHz for EIS research. The units are able to output both the DC operation point and the modulated sinewave signal as a single output. So there is no need for external modulators or other equipment. This results in a high quality signal quality with no interferences from other power electronics. Particularly important if your test bench has fieldbus communication interfaces susceptible to noise.

Any AC signal superimposed on the DC current should be as small as possible. This ensures a time-invariant system which behaves linearly, necessary for further EIS analysis. The levels of voltage response of a device under test need to be high enough to be measured adequately. This comes down to a good signal-to-noise ratio (SNR). Typical values are up to 5% of the main DC current level, which is easily within the G5’s capabilities.

Example EIS Circuit Using G5-RSS

About the G5 and Control Methods

Over 70 years of development time has been invested to ensure the G5 series meets the foreseeable needs of research organisations. The modern Si-C range of DC power systems includes the G5-RSS (bidirectional sink/source), G5-SOURCE (DC power supply) and G5-REGEN variants (DC load). 

Each system has an expansive feature set. This includes industry leading response times of <50µs for current steps, switchable capacitance, two current ranges with accuracy up to 0.003%, and a high level of safety up to PLe.

A host of control methods include USB, Ethernet, and EtherCAT interfaces, as well as a touchscreen HMI. The CANmp interface allows up to 100 messages of the CAN protocol to be customised. 

Analogue and fibre optic interfaces operate up to 48kHz, ideal when used in P-HIL systems. An Aurora protocol is available to support fast integration into platforms such as Opal-RT, Typhoon, Speedgoat and RTDS. An API for dotNET/C# programming is provided to simplify the integration into 3rd party control and measurements software platforms such as LabVIEW and MATLAB. 

The DC offset and signal modulation of the G5 are independently accessible via different interfaces. For example, the DC offset could be set via a CAN fieldbus, and the signal modulation provided via an analogue signal from an external waveform generator. The G5 handles both inputs and creates the desired DC and pulsating current as a modulated signal at the output.

Function Generator with Programmable Sweep

An embedded function generator provides users with a simple method of setting a current ripple up to 10kHz. The function generator can be accessed from an intuitive GUI, or via the touchscreen HMI of the G5. Custom waveforms can be plotted against time. Voltage/current and voltage/power relationships are also programmable where necessary.

A sweep function is included with new installations of the GUI. The feature allows changing waveforms to be easily programmed, where the output varies in frequency and/or amplitude up to the full-scale output of the device over time. Linear, stepping, or exponential rise and fall waveforms can be set.

Programming of ±100A sine wave linearly sweeping from 1Hz to 10kHz over 0.05s, then returning to 1Hz

By automatically varying frequency over time, the harmonic response of a test piece can be quickly measured across a broad range. This speeds up identification for areas of interest and unwanted resonance.

Peak voltage, current or power values are programmable as part of the sweep waveform. The function is crucial for testing components which require their response to varying voltage levels to be characterised - such as capacitors, inductors, and power converters.

Where required, parametric programming is possible. Instead of the time axis an input variable (VIN, IIN or PIN) is selected. For example, the output voltage can change automatically based on the current drawn by the load, used to emulate the characteristic behaviour of a fuel cell.

Future Proof Modular Solutions

G5 modules are available with nominals from 9kW to 54kW, at 60V to 1500V. Up to 120 units can be arranged in master/slave configurations. Outputs up to 3000V are possible into the megawatt range. Multi-module systems based around a mid-point earth create a +/- voltage output, as shown with 54kW/1500V bidirectional modules below.

If you have an outstanding requirement then contact ETPS today.

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