Multipoint digital tachograph

A multipoint digital tachograph system for measuring, storing, and displaying the amount of total time as well as time spent at or above multiple points of interest, such as at pre-programmed rotational speeds of two rotary elements, the rotary elements rotating at different but related speeds, the system including a channel for each rotary element, each channel including,

• (a) a sensor for sensing and converting to pulses the rotational speed of a rotary element,
• (b) means for converting the pulses to a voltage, to thereby obtain a voltage proportional to rotary speed,
• (c) a plurality of voltage comparators each coupled to receive said rotary speed voltage, each comparator passing a signal only after a predetermined reference voltage associated with it has been fed to it,
• (d) a plurality of AND gates each having means for energizing one input terminal thereof and having its other terminal coupled to an associated one of said voltage comparators, whereby each AND gate opens and passes a signal to its output terminal only when and after its associated voltage comparator passes a signal responsive to equality between the predetermined reference voltage and the said rotary speed voltage,
• (e) a plurality of storage registers each coupled to a respective one of said AND gates, each register storing the time its associated AND gate passes a signal from the latter's output,
• (f) means for selectively reading and for displaying the information in a selected one of the storage registers,
• (g) whereby the operation time of each rotary element, at or above a desired rotary speed as well as the total time of operation, may be displayed for inspection.