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Miniprocessor Measured Velocity and Accurate Time Interval Measurement Using Software

IP.com Disclosure Number: IPCOM000084085D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 4 page(s) / 37K

Publishing Venue

IBM

Related People

Woodward, MH: AUTHOR

Abstract

One of the major mechanical control areas encountered with an ink jet printer is carrier velocity. Should the velocity of the carrier depart from specified parameters (especially on the high end) during printing, degraded printing or hard mechanism errors or both may result.

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Miniprocessor Measured Velocity and Accurate Time Interval Measurement Using Software

One of the major mechanical control areas encountered with an ink jet printer is carrier velocity. Should the velocity of the carrier depart from specified parameters (especially on the high end) during printing, degraded printing or hard mechanism errors or both may result.

It is desirable to permit customer engineers servicing the printer to separate velocity problems from other error conditions. A logical approach to isolating velocity problems is to actually measure velocity and analyze the measured data for speed problems.

Current methods for measuring carrier velocity and diagnosing velocity problems do not lend themselves to customer engineer applications, because they are either too expensive or too bulky. It is also not desirable to add new tools to the present tool complement. An economical method of measuring velocity is described that can be inserted into the customer engineer's diagnostic software package; it is a low-cost addition to the customer engineers software package for speed measurement.

A typical ink jet printer is equipped with a 60 line per inch grating that is used by the mechanism control logic for positional feedback. The mechanism control logic counts the grating marks and uses an up/down counter to maintain the absolute position of the carrier. An associated processor (CPU) outputs positional data along with control functions (tabs, carrier returns, backspaces), and the mechanism control logic compares the processor positional data to the up/down counter for magnet dropping information.

After a comparison is made by the mechanism control logic, interrupts are generated to the processor for additional characters. Using the fact that the printer interrupts at compare points, should a carrier return be outputted followed by appropriate one unit (1/60 inch) tabs, interrupts will be generated once per period of the grating. If the time between interrupts is measured, the average velocity in increments of 1/60 of an inch can be calculated.

A software delay loop is used to measure the time between interrupts. The accuracy of the time measurement is the basic cycle time of the delay loop. This method of measuring delay is very accurate, if the pre- and post-processing time of the processor is accounted for as outlined in the next section.

Fig. 1 is a plot of the velocity versus grating position for a typical machine. The measurements are 0.9% accurate at 10 in/sec with a 16 mu s delay loop cycle. Features of interest:

1. Using one unit tabs, so that measurements can be made at 1/60 inch resolution (the smallest resolution of position available).

2. Not requiring that characters be printed; thus, removing a faulty character as a problem.

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3. Other methods of indicating overspeed may be qualitative, where this method is quantitative.

4. Adds no additional hardware to the printer electronic package.

5. Adds only ap...