Abstract
Recently, we have reported on a new magnetic field sensor having a pair of sensing elements fabricated in the turnup line shape, and made of thin Ni-Co ferromagnetic alloy film. This sensor was built in non-contact magnetic switches available in the market.
When this sensor is applied for detecting the periodical magnetic signals to be conveniently used in the automatic control systems, the output voltages of the sensor have a double frequency, and are of the magnetic flux response type. From the theoretical analysis on the output voltage, it is found that the wave form is nearly sinusoidal under the following conditions; 1) the dimensions of sensing elements are sufficiently small compared with the wave length (λ) of the periodical magnetic signals, 2) the sensing elements are kept at a distance of about (1/5) λ from the plane of the magnetic signals.
In order to obtain a more complete sinusoidal wave form, it is effective to place the pair of sensing elements at a distance of (1/2+n)λ/2. A theoretical analysis showed that the output voltages of the improved sensor are completely sinusoidal, and have a larger amplitude compared with that of anon-improved one.
An improved sensor was manufactured for trial, and applied for detecting the positions of writing in a discharge type printer. The positions of character were successfully controlled for practical use.
