modified 7 months ago

Counter Type ADC Digital Voltmeter

A digital volt meter (DVM) using a counter type ADC. This design is very similar to the ramp type DVM, but the ramp is generated by feedback from the output digital number, much like the successive approximation type DVM. It can read voltage up to around 10V with an accuracy of about 100mV. INSTRUCTIONS: The voltage source in the top left is the unknown. The 7-segment displays in the right show the result of the measurement. Wait until the counters increment to the correct amount. This example is preset to read a voltage of 1.5V. DVM Series: Ramp Type https://everycircuit.com/circuit/4592385207304192 Dual Slope Integrating Type https://everycircuit.com/circuit/6675184624599040 Integrator Type (voltage to frequency) https://everycircuit.com/circuit/6172260362354688 Successive Approximation Type (hex) https://everycircuit.com/circuit/6044286526947328 Successive Approximation Type (decimal) https://everycircuit.com/circuit/5334865438048256 Ramp Type (negative volts) https://everycircuit.com/circuit/5763215168110592 Ramp Type (auto ranging) https://everycircuit.com/circuit/6110164975091712 Tracking Type ADC https://everycircuit.com/circuit/6418942605918208 Tracking Type ADC Full Version https://everycircuit.com/circuit/4688147021299712 Flash Type ADC https://everycircuit.com/circuit/4806466994962432 Pipeline Type ADC https://everycircuit.com/circuit/5739735974412288 Pipeline Type ADC 2 Bit Stages https://everycircuit.com/circuit/6081127019970560 GENERAL: The basic idea of a counter ADC is to increase the counters until the output digital number equals the unknown input voltage. The counters will, therefore, stop at the correct number. DETAILS: The unknown voltage is fed through the top subtractor opamp (orange waveform). The clock (green waveform) increments the counters. The digital number from the counters is fed back to the 2 Digital to Analog converters (DACs) and the bottom non-inverting opamp adder. This creates the step ramp voltage (blue waveform). As the counters increment up, the ramp rises until it equals or is greater than the orange waveform. When it does, the middle comparator opamp output goes low, which stops the counters. The correct number is now displayed on the 7-segment displays. The reset signal (red waveform) resets the counters to take another measurement. The sample rate is 10ms.
published 1 year ago

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