1981-11-01

A Comprehensive Study of Digital Speedometer 811419

Performance capabilities of an electronic digital speedometer are studied. Various investigations are made for setting specifications on visual recognition time, response time, character size, visual angle, luminance, color, property of optical filter transmission, control method, stability, and the number of pulses of a speed sensor, using both experimental apparatuses and test vehicles.
As a result, followings are clarified. There is an optimum range of character sizes for a digital speedometer. Response time and stability play the most important parts in the readability. However, it is very difficult for a digital speedometer to satisfy both the stability under a constant vehicle speed and the rapid response during acceleration or deceleration, so far as a conventional control method is employed.
With the introduction of a new control method which varies the refresh cycle of display, the performances of both the stability and the rapid response are improved.

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