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Browse Prior Art Database

Digital Tachometer with Scaling

IP.com Disclosure Number: IPCOM000050231D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Blevins, BJ: AUTHOR [+2]

Abstract

The disclosed digital tachometer accepts input encoder pulses produced by a moving member and generates an output speed signal that is directly proportional to the speed of a moving member.

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Digital Tachometer with Scaling

The disclosed digital tachometer accepts input encoder pulses produced by a moving member and generates an output speed signal that is directly proportional to the speed of a moving member.

The figure illustrates a functional diagram of such a digital tachometer which accepts input encoder pulses 1 from an optical device that provides pulses in response to sensing the passing of physical marks on a moving member, and generates an output speed signal at output 2. The time between the encoder pulses is measured and used to select a corresponding speed from a table stored in read only memory (ROM) 3. This digital tachometer can be programmed for a desired speed resolution and can be scaled for increased dynamic range during operation.

An Exclusive OR gate 4 is used to prevent speed errors due to overlapping of encoder pulses 1 as a result of, for example, the slow speed of the moving member producing the pulses. Divide by two functional blocks 5 along with four d() divided by dt functional blocks 6 (which reduce encoder pulses 1 to only edges) provide for four different speed resolutions. Speed is scaled with a two- bit scale factor represented by block 7 which selects the encoder pulse edges
(i.e., resolution) to be used for subsequent timing measurements. Time counters 8 count clock pulses from a stable time base 9. The count accumulated between the selected edge pulses along line 10 is then stored in temporary storage 11. This coun...