EMG NEEDLE ELECTRODES - ELECTRICAL-IMPEDANCE

  • 1 January 1979
    • journal article
    • research article
    • Vol. 60  (8) , 364-369
Abstract
The electrical impedance of stainless-steel monopolar needle electrode and concentric electrode samples from 3 manufacturers were measured in 154mM saline solution using sine-wave excitation at 4 frequencies from 10Hz to 10kHz. Current densities of < 2.5 .times. 10-5 amp/cm2 were used. Needle and fine-wire electrode measurements were also made in live rats. Linear dimensions of exposed tips were measured from which exposure areas were calculated. Surface areas of the monopolar needles varied between 0.06 and 0.15mm2. Presoaking electrodes for 20 min in saline solution containing a small wetting agent concentration produced a 6-fold to 20-fold impedance reduction. Average impedance magnitudes of the monopolar electrodes ranged from 1.4 megohms (M.OMEGA.) at 10Hz to 6.6 kilohms (k.OMEGA. at 10kHz). The phase angle of impedance due to the capacitive component of needle-electrolyte impedance ranged between -45 and -71.degree.. Impedance reduction resulting from presoaking and concomitant reduction in electronic noise would be an advantage in observing low-amplitude potentials.

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