Browse Prior Art Database

Verifying Tachometer Operation

IP.com Disclosure Number: IPCOM000075113D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Van Pelt, RW: AUTHOR

Abstract

In precision web transporting systems, such as a magnetic tape drive, digital tachometers are used for metering displacement and indicating velocity. Defective tachometer disks, such as ones exposed to dirt and the like, as well as degradation of electronic circuits, can cause tachometer malfunctions. It is desirable to predict these malfunctions or detect them on an automatic basis. Visual inspection of a tachometer disk is not satisfactory for this purpose.

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Verifying Tachometer Operation

In precision web transporting systems, such as a magnetic tape drive, digital tachometers are used for metering displacement and indicating velocity. Defective tachometer disks, such as ones exposed to dirt and the like, as well as degradation of electronic circuits, can cause tachometer malfunctions. It is desirable to predict these malfunctions or detect them on an automatic basis. Visual inspection of a tachometer disk is not satisfactory for this purpose.

Tachometer disk 10 is driven by motor 11. Incandescent lamp 12 shines light through disk 10 to photodetector 13 which supplies its signals to pulse former 14. In the illustrated tachometer disk, the dark areas and the light areas may have equal lengths, such that pulse former 14 supplies output squarewave 15 when everything is properly operating. If a light area is obliterated, signal 16 is provided resulting in a missed tachometer count. Also, on the other hand, a partial covering of transparent areas may result in erroneous tachometer signal 17. Marginal operation is indicated by signal 18.

Verification that the tachometer system is operating properly is accomplished by coaction of I/O controller 20 and a computer program in CPU 21. Alternatively, all of the analysis can be provided in an I/O controller.

In this disclosure, detector 25 of I/O controller 20 detects the signal-state changes and supplies actuating pulses over line 26 to toggle switch 27 between its alternate output terminals.

Tachometer signals are supplied over line 28 to both detector 25 and switch 27. A pair of meters 30 and 31 meter the time between successive transitions in alternating half-cycles of the tachometer signal. A time meter may include oscillator 32 actuating counter 33.

An actuating signal on line 26 clears the respective counters and simultaneously transfers the count through AND circuits 34 and 35 to buffer registers 36 and 37. Oscillato...