Solving the Challenges in Impedance Measurement

In this interview, Applications Manager at Zurich Instruments, Dr Tim Ashworth, discusses the latest innovations in Impedance Analyzers.

Dr Ashworth explains the main challenges in the field of impedance measurement and how innovative analyzers can be used to help overcome them.

Please tell us about Zurich Instruments and your role within the company?

Zurich Instruments is based in Zurich, Switzerland, with offices in Shanghai and Boston. We are a test and measurement company offering lock-in amplifiers, arbitrary waveform generators, quantum computing control systems, and impedance analyzers.

By integrating an ever-increasing amount of functionality into our class-leading hardware without sacrificing ease of use, Zurich Instruments strives for innovation leadership in the field of signal processing.

Consequently, our customers benefit from reduced setup complexity and efficient workflows. This helps them to save time and focus on their ultimate goals.  

As a company, Zurich Instruments is young, dynamic and always innovating and improving. As applications manager for our impedance products since the release of the MFIA in 2016, my role has been to navigate the multifaceted impedance market and provide our customers with tools that suit their current and future needs. This role takes me all over the world to visit conferences and customers, and is both challenging and rewarding.

What are the key challenges faced in the field of impedance measurement?

Measuring impedance as a function of frequency is a well-known method of characterizing components and dielectrics, as well as many other types of materials.

However, to date there has been little innovation in impedance analyzers. Therefore, many instruments are limited by their streaming rate, measurement speed, or by a lower frequency limit that misses the interesting frequency ranges.

Furthermore, as the frequency is swept, the impedance may change by many orders of magnitude. This means that an instrument needs to be capable of handling a broad range of impedance values to get great data.

When connecting the instrument to the sample, further challenges arise. Typically, a dedicated cable or fixture is needed to make the connection. This fixture can reduce the accuracy of the impedance data by introducing parasitics. Counteracting these parasitics is of key importance.

How can innovations in impedance analyzers help to overcome these challenges?

The MFIA impedance analyzer from Zurich Instruments provides an innovative approach to impedance analysis. It eliminates the need for the feedback loop common to many instruments by directly measuring the voltage across and current through the device under test.

This means that the MFIA can measure impedances up to the teraohm level and frequencies down to millihertz. This also allows for fast impedance measurements on a timescale of ten microseconds, which is very important for sensor characterization.

The real magic, however, lies in the software. The MFIA is controlled by LabOne, a powerful software interface that runs all products from Zurich Instruments. LabOne includes many user-friendly tools: an example is the Parametric Sweeper, which allows the user to sweep parameters such as test signal level, bias voltage or frequency, and measure impedance parameters as a function thereof.

This results in seamless data from 1 mHz to 5 MHz with very high data point density. The data is displayed in real time and the resulting multi-trace graph can be quickly adjusted and exported in vector graphics, ready for publication.

Another innovation in an impedance analyzer is the addition of time-domain tools. The DAQ tool and the Plotter tool of the MFIA allow for the time evolution of impedance values to be measured quickly and analyzed either as triggered shots or as a continuous data stream.  Thanks to the 60 Msa/s ADC, the Scope tool provides a real-time view of the raw voltage or current data.

What sets the MFIA apart from other impedance analyzers and how does it compare to other models available on the market?

The MFIA features LabOne, which is an industry-leading software interface complete with multiple tools that help to speed up the process of bringing the data from bench-top to publication.

The MFIA also includes a unique Confidence Indicator, which ensures that the data is accurate and reliable. This flags up any data point is based on unreliable fundamentals.

Therefore, the delivered data is not just reliable, but also accurate, with a basic accuracy of 0.05%. In addition, the comprehensive accuracy chart clearly shows the accuracy for a given parameter set.

What are the benefits of integrating the MFIA with the MFLI lock-in amplifier?

One of the unique features of the MFIA is that it also includes the full functionality of the MFLI Lock-in Amplifier from Zurich Instruments. This provides users with the power to measure small periodic current and voltage signals that would otherwise need an additional standalone instrument.

Launched in 2015, the MFLI has already become the new standard in the world of lock-in amplifiers.

How can Zurich Instruments help users who are new to the field of impedance measurements?

As well as the Confidence Indicator, which ensures trust in measured values for both new and seasoned users, Zurich Instruments also includes a Compensation Advisor. This guides the user through the process of compensating the fixtures connecting the sample to the instrument, so reducing uncertainty when using those vital fixtures.

Which application areas do you see most interest from?

MFIA is perfect for application fields such as sensor characterisation or transient spectroscopy because of its fast measurement time and high precision.

In any application field where low- to mid-frequency impedance needs to be precisely or accurately measured, the MFIA is a powerful tool. It is also useful when high impedances needs to be measured. For example, there is a lot of interest from researchers in component characterization (supercapacitors and high-Q capacitors), bio-impedance and dielectrics.

What level of support can users expect with the MFIA?

Every instruments comes with our premium customer care package, and Zurich Instruments has a team of PhD-level scientists and R&D engineers who have extensive practical lab experience and are available to help with impedance challenges.

For example, Zurich Instruments publishes regular blog posts on measuring challenging impedances. Recent articles covered equivalent series resistance (ESR) of a supercapacitor, measuring the low equivalent series inductance (ESL) of DC-Link capacitors, and fast capacitance measurements.

What does this mean for the future of impedance measurement?

The MFIA brings innovation to a key area of research that has been long neglected by instrument builders. It allows users to acquire accurate data confidently.

Where can our readers go to find out more?

Have a look at the Zurich Instruments website, which contains some excellent application notes and blog posts explaining recent results on challenging subjects: www.zhinst.com.

Alternatively it is possible to call or email Dr Tim Ashworth, who is always happy to hear about new impedance challenges.

About Tim Ashworth

Dr Tim Ashworth obtained his PhD degree at the University of Manchester, UK in the field of nanoscale surface science, focusing on UHV SPM. Tim subsequently worked as a post-doc at the University of Basel, using lock-in technology and PLLs to get the best possible results from their home-built SPM.

Tim built up over eight years’ experience of worldwide applications support and scientific business development, before joining Zurich Instruments in 2016.

In addition to strengthening the SPM knowledge at Zurich Instruments, Tim is an applications manager for impedance products.

Disclaimer: The views expressed here are those of the interviewee and do not necessarily represent the views of AZoM.com Limited (T/A) AZoNetwork, the owner and operator of this website. This disclaimer forms part of the Terms and Conditions of use of this website.

Acknowledgements

Produced from material originally authored by Mychealla Rice, AZoNetwork,