Ratemeter

Claim 1

A ratemeter comprising: A. sensing means responsive to re-occurring events, for providing an electrical output, timing, pulse of a first polarity upon the occurrence of each event; B. timing means responsive to each said output pulse of said sensing means for providing, successively, and on a reoccurring basis, first, second and third discrete electrical levels, said first and second electrical levels being of predetermined duration and the duration of said third level being equal to the period between said output pulses less the total duration of said first and second electrical levels, and wherein said timing means comprises: 1. a differential amplifier having a first input, a second input and an output, said first input and said output being of like phase and said second input being of opposite phase to that of said output, 2. first circuit means connecting a portion of the output voltage present on said output to said first input and including first switching means connected to said first input and responsive to a second polarity output of said amplifier for shorting said first input, 3. second circuit means comprising: a capacitor having one terminal connected to a reference potential, a resistor connected between the other terminal of said capacitor and said second input, a circuit connecting said output through said resistor to said capacitor, and second switching means connected across said resistor and responsive to a second polarity output of said amplifier for shorting said resistor between said capacitor and said second input, whereby with an initial condition of zero voltage on said inputs there exists a zero voltage as said third discrete electrical level on said output, a said first polarity timing pulse applied to said first input causes said amplifier to provide a maximum first polarity output, or first discrete electrical level, which output is coupled to said capacitor which commences charging in a first polarity direction to provide an increasing amplitude first polarity input to said second input and timing the duration of said first discrete electrical level, when the level of said first polarity voltage on said second input exceeds the level on said first input the differential input of said amplifier switches polarity and the potential on said output changes to a maximum second polarity value as said second discrete electrical level, and said second switching means is operated by said second polarity from said output shorting said resistor and causing said capacitor to commence discharging, timing said second discrete electrical level, and when the voltage on said second input is pulled down to a point which causes the differential amplifier to abruptly change from said second electrical discrete level to a neutral state with a zero output, said third discrete electrical level is provided on said output, which level remains until the re-occurrence of a said timing pulse; C. decay circuit means responsive to the output of said timing means and to the initiation of said second electrical level for establishing a reference voltage and including time constant means responsive to the initiation of said third level for providing a voltage which initially corresponds to said reference voltage, then decays during said third electrical level to a decayed level, and including means responsive to the next occurring said first electrical level for halting said decay and holding the decayed level for the duration of said next occurring first electrical level; and D. sample and hold means responsive to said decay circuit means and said decayed level for providing a substantially continuously level output proportional to the last held decayed level and which is representative of the rate of occurrence of the last two successive said events.