| 摘要 |
A series of holes spaced along the length of a web is sensed optically and corresponding pulses are counted in a first counter. Simultaneously a running web length measurement is performed by an encoder wheel, which supplies encoder pulses to a second counter that counts down from a preselected number. When the count in the first counter reaches a selected value, the count in the second counter represents deviation of a measured "board length" from a standard, which is displayed digitally. A display indicates whether the deviation from the standard is inside or outside of a selected range and, if outside, indicates whether the measured web length is shorter or longer than a standard length. Hole simulation pulses are generated to compensate for missing hole pulses, and data readout is inhibited if the final count in the first counter is produced by a hole simulation pulse. A strobe inhibit circuit avoids errors when a strobe light is used to inspect the web.
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