For fun I decided to test a small glass of salt water for linearity as a resistance. The electrodes were strips of stainless steel (in fact the spring strips from old windscreen wiper blades!). This was added to a divider circuit with 680 ohms as the lower leg. My QA403 was used to plot various aspects of this resistor's performance:
At the standard 1kHz the typical distortion v. level curve shows up:
The linearity increases with frequency:
This might be due to impedance falling, or polarization or perhaps something else (scope for further investigation), I forgot to check if the gain varied with frequency
Seems to be mainly 3rd harmonic (makes sense as the cell is symmetric):
Residual at 60Hz:
At the standard 1kHz the typical distortion v. level curve shows up:
The linearity increases with frequency:
This might be due to impedance falling, or polarization or perhaps something else (scope for further investigation), I forgot to check if the gain varied with frequency
Seems to be mainly 3rd harmonic (makes sense as the cell is symmetric):
Residual at 60Hz:
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