What you need to know when choosing a product
There are a couple of things to consider when choosing the right impedance measurement device. First, you should choose the right type and arrangement of electrodes for excitation and response measurement with the object. Very often, the electrodes have to be custom made as well.
Here are some of the key aspects to consider when choosing the right device:
– What frequency range of measurements does your use case require?
– What is the necessary signal excitation energy?
– Should you use current or voltage for excitation?
– How fast do you need to measure?
– Where are you measuring, e.g. inside or on the surface of the sample?
In order to get significant and accurate measurement results, all of these criteria have to be precisely thought through.
What are the options?
There is a wide range of commercially available impedance analysers, however, there are only a few good options for embedded measurement. We dug deep into product manuals and specifications to outline the best options on the market today. The following table is an overview showing the key features of the impedance analysers best suited for a new product design.
Table 1. Embeddable impedance measurement device comparison
(1) Indicated accuracies can vary heavily depending on the specific set-up of measurements.
(2) Indicated dimensions are for modules, embeddable versions are more compact.
Integrated circuit chips are a great choice if your product has to be wearable. For example, a smart-watch that has the capability to measure bioelectrical impedance, which gives the user information about their body fat, muscle mass and body fat percentage in addition to the usual features. Body composition analysers in general only use one set frequency for the measurements, so narrower frequency range and only single-frequency option aren’t really obstacles for the device’s performance.
Complex objects require advanced features
More often than not, the phenomena of interest are complex and require electrical impedance spectroscopy to obtain useful information. In order to get a better picture of these phenomena, you need a device that measures on multiple frequencies, which is what spectroscopy means.
Single-frequency devices can also perform spectroscopy with the help of frequency sweeping function. This means that they measure multiple frequencies one at a time. Still, for the user, it is more time consuming and not suitable for monitoring rapid processes.
Although many hand-held and portable devices have embedded microchips that measure bioelectrical impedance, more advanced devices require better accuracy. When developing medical devices, the results need to be reliable and accurate every time. This is where chip-based impedance measurement technologies often fall short.
Overall, there’s a range of technologies on the market for developing products with impedance measurement capabilities. However, different applications all come with their own set of requirements for size, speed, and accuracy. Make sure you know what works best for your case.