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I have recently started looking into transducers to measure a natural physical phenomena. The sensors I read about, especially electrochemical sensors like interdigital electrodes use a sinusoidal signal to enable the sensor electrodes. I came across this post, but it does not really answer my question.

Why do these sensors use sine signal but not square signal or even triangle waves? Perhaps some experimentation would help me understand what I would see on oscilloscope but unfortunately I do not have access to one at the moment or any electrodes to experiment with, hence my question.

JRE
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David Norman
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    Ah, sine waves are always smooth, but square wave always have spikes (over shoot, ringing etc) at high low change overs. These abrupt changes are actually very high (multiple) frequency signals (for a short period though) disturbing the sensors. Moreover, sine wave are created very pure, consists of fundamental and lower amplitude, secondary, third harmonics etc . On the other hand square waves are actually formed by a long series (Fourier) of harmonics. (Don't ask me who is Fourier, I forgot. I only mention the name so that my bad friends would respect more than I deserve.) – tlfong01 Aug 19 '20 at 05:13
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    I really don't know, but I think that it's because the sine wave is the purest and *the most natural* wave. Radiations from humans and almost all creatures (including the plants) are sine waves. And, of course, it's possible to model everything with sine waves. – Rohat Kılıç Aug 19 '20 at 05:18
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    @tlfong01, thank you for your answer and you got my respect for explaining that to me. – David Norman Aug 19 '20 at 05:43
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    @RohatKılıç, you are right, come to think of it, sine wave is naturally occurring whereas square waves are filtered sine waves. – David Norman Aug 19 '20 at 05:44
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    @DavidNorman: Square waves are **not** filtered sine waves. Square waves are the [**sum** of multiple sine waves.](https://en.wikipedia.org/wiki/Square_wave#Fourier_analysis) – JRE Aug 19 '20 at 05:50
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    @JRE, thank you for correcting me, i always thought otherwise. there is a huge gap in my knowledge – David Norman Aug 19 '20 at 06:36
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    If the sensors are not pure resistances, the analysis with a sinusoidal input will be easier. – Chu Aug 19 '20 at 17:11

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