The Measuring Instrument with Magnetic Amplifier for Electrolytic Corrosion Jiro Yamaguchi and Yoshibumi Sakurai From the preventative point of view for electrolytic corrosion, it is important that the sheath current and the cable potential are recorded continuously. Since the conventional electrical recording meter requires a considerable electric power, the d-c (and low frequency) amplifier is used to amplify the measuring voltage. In this report the magnetic amplifiers which are designed for this purpose are described. Bridge type magnetic amplifier circuits are adopted and push-pull connection are used to obtain good stability. Mc-permalloy (amplifier I) and 50-Ni-permalloy (amplifier II) are used as the core material. As voltage source, either power frequency line or battery are usable. In the latter case, d-c voltage is converted to a-c rectangular wave by the mechanical interrupter (90 c/s).
The recording instrument (±5V full scale) has 43Ω internal resistance. The maximum input for amplifier II are
±0.48mV. for current measurement ±740mV for potential measurement
and 63% response time are 0.05 and 0.08 second respectively. In amplifier I, the maximum input voltage is about twice, while response time is about one-half.
Since these devices has rugged construction and good stability, it is clear that they are suitable for the field test.
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