Shown here are screen captures from my scope for excitation frequencies of 12.8 kHz (a) and 119 kHz (b), respectively.įor chemical and biological purposes, impedance spectroscopy is performed using voltages less than 2 V pp, so the AD5933’s output voltage ranges are well-suited to the task. The 100,000 Hz upper frequency limit of the AD5933’s DDS would have been a cinch for them to design. Analog Devices makes DDS devices that can produce sine wave signals up into the hundreds of megahertz range.

The AD5933 generates the required excitation sine wave using a Direct Digital Synthesis (DDS) block. The basic AD5933 functional block diagram is shown in Figure 1. Later, I’ll discuss the additional circuitry that can be added to the AD5933 to minimize these shortcomings. However, for other applications, its excitation output amplifier has some shortcomings, as does the transimpedance amplifier used for the current-measuring input. The Analog Devices AD5933 contains almost everything you need to do impedance spectroscopy for certain applications. I am guessing that this last use case was what Analog Devices engineers had in mind when they designed the AD5933 Impedance Converter chip. Such measurements can be particularly viable if the EIS instrument is made at a low cost and miniaturized. In situations where it’s difficult to use the common visual inspection method, EIS can be used instead. In the biomedical field, its uses include detection and identification of specific forms of viruses in blood samples.ĮIS is also useful for monitoring corrosion in metals, such as aluminum and steel. However, it can also be used to measure electrochemical processes, in which case it is called Electrochemical Impedance Spectroscopy (EIS). For electronics enthusiasts, common uses would be measuring the impedance of transducers such as speakers and microphones. Impedance spectroscopy is the measurement of a device’s impedance-or resistance-over a range of frequencies.

I recently came across a chip made by Analog Devices that performs nearly all the functions needed to do impedance spectroscopy. As a result, I’ve designed many voltammographs and conductivity meters over the years. I’ve built and serviced many instruments for university chemistry teaching labs.

In this article, he explores the technology, circuit design and software that serve these efforts. From IC to Instrument Brian discovered an Analog Devices chip that enables you to perform impedance spectroscopy-in other words, it can measure impedance over a range of frequencies.

Impedance analyzer with external clock