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Acoustic Tape Loop Position Sensing

IP.com Disclosure Number: IPCOM000073707D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Roth, O: AUTHOR [+2]

Abstract

Acoustic sensing provides continuous position and direction of travel information of a tape loop in the vacuum column of a magnetic tape unit. A 37.5 KHz acoustic transmitter-receiver system senses the position of the loop of tape 1 in vacuum column 2 of a magnetic tape unit, and the output of transducer 3 is used to control reel drive motor 4. A piezo-electric transducer is used. The operating frequency is 37.5 KHz. The range of possible operating frequencies is from 20 KHz, established by the vacuum column noise, to 100 KHz, established by air attenuation. The width 5 of the column is approximately 2-1/2 inches. The depth 6 of the column is approximately 1/2 inch. The column forms an acoustic wave guide because of the acoustic mismatch between the air and the aluminum or glass walls of the column.

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Acoustic Tape Loop Position Sensing

Acoustic sensing provides continuous position and direction of travel information of a tape loop in the vacuum column of a magnetic tape unit. A 37.5 KHz acoustic transmitter-receiver system senses the position of the loop of tape 1 in vacuum column 2 of a magnetic tape unit, and the output of transducer 3 is used to control reel drive motor 4. A piezo-electric transducer is used. The operating frequency is 37.5 KHz. The range of possible operating frequencies is from 20 KHz, established by the vacuum column noise, to 100 KHz, established by air attenuation. The width 5 of the column is approximately 2-1/2 inches. The depth 6 of the column is approximately 1/2 inch. The column forms an acoustic wave guide because of the acoustic mismatch between the air and the aluminum or glass walls of the column. The transducer is operated in a pulsed mode. The pulse width time is determined by the bandwidth of the transducer, and the need to eliminate cancellation phenomena caused by multipath reflection from the tape loop and side walls of the column. The transducer is mounted in launching section 7, which also contains vacuum port 8. The walls of this section are sloped at least 45 degrees and serve as a match between the transducer and the vacuum column. The output of the transducer, when operating in its receiving mode, is processed by control circuit 9 to provide information both as to the position of the tape loop and as to the up or...