| 摘要 |
The invention permits four-place digital rotational speed measurement in passenger cars and trucks both with petrol engines and with diesel engines. The digital revolutions counters available to date mostly permit only a two-place display. This is unsatisfactory, above all in the low rotational speed range. The problem resides in generating a high pulse sequence proportional to rotational speed. The frequency mostly obtained at the contact-breaker point is too low for this purpose. There is a plurality of possibilities for generating a high frequency proportional to rotational speed, but most methods are accompanied by technical and/or economic disadvantages. The solution is, then, to obtain pulses from the generator by transmitting the three-phase alternating current, which is present before the bridge rectifier (Figure 1), into the display electronics optoelectronically. It is now possible in this way to obtain, e.g. by using only one phase, 2400 instead of 200 pulse/sec. The technical outlay for this is very low, and owing to the optoelectronic coupling this method is largely interference-free. Apart from rotational speed measurement, the invention can also be used as a digital speed limiting device. <IMAGE>
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