impedance variation detector

In order to measure small changes in high resistance circuits, the use of a simple ohmmeter is not sufficient, since the measurement can be distorted by the effect of voltage transients originating both from the object being measured as well as other sources of interference. These errors can be largely eliminated however, by employing an AC-voltage of a suitable frequency (e.g. 10 kHz) along with a selective filter. This method will measure not only changes in resistance, but will also indicate variations in the AC impedance of a circuit. The detector can be used to indicate changes of the impedance of the human body, of animals or I even of plants, which are the result of muscle contractions, changes in mood, external stimulae etc.