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My finest work so far, if I may say so myself! This
digital volt meter (DVM) using a tracking Analog to Digital Converter (ADC). It can read a voltage up to around 10V with an accuracy of about 100mV. Does not work on voltage at or below 0V, or voltage at or above 10V. Also, the jitters in the last digit are normal for a tracking ADC. These things will be fixed in my next version (I hope).
Next full version for those interested https://everycircuit.com/circuit/4688147021299712
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
Counter Type ADC https://everycircuit.com/circuit/4509930926899200
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
INSTRUCTIONS:
The voltage source on the left is the unknown. The 7-segment displays on the right show the result. The displayed number will oscillate around the correct amount. (Currently set to 1.8V).
GENERAL:
The third type of voltmeter to use digital feedback (the others are successive approximation and counter). The circuit uses a tracking ADC to increase the counters until the output digital number equals or passes the unknown input voltage. Then the counters reduce by one. Then increase by one. This repeats. So the number displayed is always close (tracks) to the unknown voltage. A unique feature is lack of reset signal.
DETAILS:
The unknown voltage is feed through the top subtractor opamp (orange waveform). The digital number from the counters is feedback to the 2 Digital to Analog Converters (DACs) and the bottom non-inverting opamp adder. This creates the step voltage (blue waveform). The middle comparator opamp goes high if the blue is lower than the orange (count up). Else it outputs low (count down).
The green waveform is the "decide next operation" clock. The red waveform is the "load operation into the counters" clock. There are 4 main states:
Normal increment top counter (middle flip-flop)
This happens when the comparator is high.
Normal decrement top counter (middle flip-flop)
This happens when the comparator is low.
Increment bottom counter and reset top counter (bottom flip-flop)
This happens if the digital output number is 09,19,29,39,49,59,69,79,89 and we want to count up (comparator high). This state overrides the normal increment state. The logic gates detect this.
Decrement bottom counter and load 9 into top counter (top flip-flop)
This happens if the digital number is 10,20,30,40,50,60,70,80,90 and we want to count down (comparator low). This state overrides the normal decrement state. The logic gates detect this.
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