Voltage to Time A/D converter (Ramp type)
Any digital voltmeter has a fundamental cycle
sequence which involves sampling, display, and reset sequence. The
application of input voltage initiates the measurement cycle. The
oscillator is automatically switched with the operator and its output
consists of pulses which are counted by an electronic counter. A units
counter is first actuated. This units counter provides a carry pulse to
the tens counter on using the counter input pulse. In turn, the tens
counter provides its own carry pulse after it has counted 10 carry
pulses from the units counter. If excess input voltage is being
measured, it provides its own carry pulse which switches on a warning
lamp.
Each decade counter unit in a DVM is counted
as a D to A converter. Outputs of a D to A convertor are connected in
parallel which build up a comparison voltage. At the instant when the
comparison section senses that the input voltage and comparison voltages
are equal, it produces a trigger pulse which stops the oscillator.
voltage to frequency converter
A voltage-controlled oscillator or VCO is an electronic oscillator whose oscillation frequency is controlled by a voltage input. The applied input voltage determines the instantaneous oscillation frequency. Consequently, modulating signals applied to control input may cause frequency modulation (FM) or phase modulation (PM). A VCO may also be part of a phase-locked loop.
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