Browse Prior Art Database

Position Determination Using Pulse Delays

IP.com Disclosure Number: IPCOM000043695D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

Koperda, FR: AUTHOR [+2]

Abstract

This invention provides a means of accurately measuring distances in a very short period of time in order to know the velocity of the object and to implement variable character-per-inch densities. The distance to an object can be determined by measuring the time delay of a pulse from its transmission to the reception of the pulse. A transmitter may be provided which produces a magnetic field that is transmitted to a receiving coil. The receiving coil blocks the electric field by using a conductor over it. As the magnetic field passes through the coil, it produces an electrical pulse that propagates to a receiver. Since the coil of the receiver is a very large inductor, the received pulse propagates very slowly. Typical pulse delays are about ten microseconds. Referring to Fig.

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Position Determination Using Pulse Delays

This invention provides a means of accurately measuring distances in a very short period of time in order to know the velocity of the object and to implement variable character-per-inch densities. The distance to an object can be determined by measuring the time delay of a pulse from its transmission to the reception of the pulse. A transmitter may be provided which produces a magnetic field that is transmitted to a receiving coil. The receiving coil blocks the electric field by using a conductor over it. As the magnetic field passes through the coil, it produces an electrical pulse that propagates to a receiver. Since the coil of the receiver is a very large inductor, the received pulse propagates very slowly. Typical pulse delays are about ten microseconds. Referring to Fig. 1, the transmitting coil 10 consists of two turns of wire. A pulse of 1.5 amperes is applied for one microsecond. The receiver consists of a high frequency ferrite bar 12 with wire wrapped along its entire length. The coil is then put into an aluminum shell. The aluminum blocks all external electric fields, but allows the magnetic field of the transmitter through it. Since the transmitter is circular, no fixed distance from the transmitter to the receiving coil is needed. In other words, the induced voltage into the receiving coil remains the same, independent of any vertical movement of the transmitter. This allows for ease of manufacturing and wear of parts. The accuracy of the measurement of the distance is controlled primarily by two factors. The first is the width of the wire used on the receiving coil. The desired resolution is 300 lines-per-inch. The coil is wound with a spacing of 400 turns-per-inch. To minimize fringe effects, the transmitter is located at a minimum of two wire diameters away from the receiving coil. The other factor that determines the accuracy is the measurement of the width of the received pulse. Where the desired horizontal accuracy is 300 lines-per-inch, and the width of travel is about 15 inches, the number of points is 300 lines/inch x 15 inches = 4500 lines. The delay through the coil is ten microseconds. Therefore, the oscillator to measure the pulse should be 4500/10-5 = 450 MHz. The digital counter 15 measuring the number of counts in ten microseconds will be 4500 counts. Variable character-per-inch fonts are easily implemented by changing the frequency of the measuring clock. For example: At ten characters-per-inch and ten dots-per-character and 132 characters-per-line, there are 1320 dot options per 13.2 inches. If the oscillator is adjusted so that 1320 counts are measured in the ten-microsecond gating period, then each count represents one dot option. If the character-per-inch density is doubled to 20 characters-per-inch, then the oscillator is adjusted for a count of 2640. In reality, the counts are set for double the needed resolution. To be able to calibrate the oscillator...