Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Position Sensor

IP.com Disclosure Number: IPCOM000086635D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 70K

Publishing Venue

IBM

Related People

Cannon, MR: AUTHOR

Abstract

This is an accurate position locating device, which, in its simplest form, includes a pair of conventional magnetic recording heads that are positioned to move relative to one another and to output an electrical signal having a null-point occurring at a selected home position.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Position Sensor

This is an accurate position locating device, which, in its simplest form, includes a pair of conventional magnetic recording heads that are positioned to move relative to one another and to output an electrical signal having a null-point occurring at a selected home position.

In Fig. 1(A) a write head and a read head are positioned with parallel gaps. Arrows 10 and 12, respectively, depict the direction of motion of the heads, which is normal to the gaps. Fig. 1(B) depicts the home position, when the gaps are in alignment. In this case the flux from the write head passes through the read head in a normal manner. When the gaps are misaligned, as shown in Figs. 1(A) and 1(C), the flux from the write head passes through one of the read-head pole tips. The write head can be energized with DC current, in which case the read- head flux and output signal are approximately as shown in Fig. 2 (assuming constant velocity). The flux through the read head peaks at a point where the two gaps are exactly aligned. At a distance (perhaps 20 to 30 mu-inches) on either side of the alignment point, the read-head flux is zero. The output voltage from the read head is as shown in Fig. 2(B), if the velocity is constant. The null point between the positive and negative pulses coincides with the peak flux position or perfect gap alignment.

When velocity is not constant, the output signal, as depicted in Fig. 2(B), will be distorted and the null point may not coincide with perfect alignment. In this situation, velocity sensitivity may be eliminated by exciting the write head with AC excitation, which causes the write head to produce a read signal, as shown in Fig. 3. This arrangement operates down to zero velocity. A threshold T may be established to determine when the transducers are aligned.

Fig. 4 depicts an alternative technique for locating home position by using an MR read head and a conventional write head. In Fig. 4(A), no flux from the write head enters the MR element. The direction of flux flow is indicated by arrow 14. As the heads move to the position shown in Fig. 4(B), the flux pa...