| 摘要 |
A system for producing an indication of the number of occurrences of certain events, such as the traversal of miles by a vehicle, in which a single-pole double-throw reed switch is operated between its two positions in proportion to the number of occurrences of events to be counted; the two positions of the reed switch produce two different corresponding states of a first bistable multivibrator, the output of which is differentiated and clipped in a special clipping circuit to remove one polarity of differentiated pulse. The remaining differentiated pulses are applied to pass a predetermined amount of charge per pulse through an electrochemical storage cell, whereby the amount of plating of metal from one electrode to the surface of the other at a given time is proportional to the number of differentiated pulses supplied thereto and therefore proportional to the number of events that have occurred. when an indication of this number is desired, a reading current is passed through the electrochemical storage cell in the opposite direction to the current caused by the differentiated pulses, and the time when substantially all of the metal in the cell has been replated upon the original electrode is sensed by an increment in the voltage across the cell. The intensity of the reading current is substantially constant, so that the duration of the reading time provides an indication of the amount of material which had been plated and hence an indication of the number of said events which has occurred. The reading current is automatically and promptly terminated by means of a second bistable multivibrator circuit in response to the above-mentioned increment in cell voltage. Clock pulses are passed through an AND gate only during the reading-current time, thereby to produce a number of clock pulses proportional to the number of occurrences of said event. A common supply-voltage source is utilized for the first multivibrator and for the reading-current circuit, whereby undesired effects on the first multivibrator of variation in supply voltage are largely cancelled by corresponding changes in the intensity of the reading current. The clipping of the differentiated pulse not used for operating the electrochemical cell is accomplished by means of a semiconductor rectifier diode which is effective for voltages above about 0.6 volt and the portion of the pulse below this voltage is effectively removed by a shunt transistor turned on by the rectangular pulse from which the differentiated pulses are derived.
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