NOISE,TEMPERATURE COEFFICIENT,AND LONG TIME STABILITY OF ELECTRODES FOR TELLURIC OBSERVATIONS* |
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| Authors: | G PETIAU A DUPIS |
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| Abstract: | Numerous electrodes, already used in geophysics or just perfected by us, have been compared by measuring the three main characteristics which interest the user: noise spectrum, temperature coefficient and polarization with its stability versus time. Among the most used unpolarizable electrodes, silver-silver chloride (Ag-AgCl) are the best ones. But a systematic research of all different possible metal-salt couples, have led us to use lead-lead chloride (Pb-PbCl2) for the following reasons: noise as low as the one of Ag-AgCl at 1 Hz and even lower for the low frequencies (0.4 μV at 1 Hz and 1.2 μV at 0.01 Hz for peak to peak value and ΔF=F), temperature coefficient about ten times weaker (?40 μV/°C instead of ?450 μV/°C) and also better long time stability of the polarization (1 mV/month instead of 2 at 10 mV/month). We have been using these electrodes since 1977 as “tube” electrodes which are very easy to use. They allow us to record correctly the fast variations thanks to their low noise, the very slow variations, their low temperature coefficient and their stability, and this with telluric lines only about 100 m long. |
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