Here is a great digital volt meter (DVM) based on the flash analog to digital converter (ADC). Its range is 0 to 10V accurate to 1V.
INSTRUCTIONS:
Adjust the voltage source in the top left, and the result will be instantly shown on the 7-segment displays in the top right. This example reads 10V.
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
Tracking Type ADC https://everycircuit.com/circuit/6418942605918208
Tracking Type ADC Full Version https://everycircuit.com/circuit/4688147021299712
Pipeline Type ADC https://everycircuit.com/circuit/5739735974412288
Pipeline Type ADC 2 Bit Stages
https://everycircuit.com/circuit/6081127019970560
GENERAL:
Probably the simplest type of voltmeter to understand, the flash ADC uses an array of opamp comparators to detect the unknown voltage level. Each comparator is set to trigger at sequential voltage levels created by the voltage divider and the reference voltage. As the unknown voltage rises, sequential comparators will saturate. A priority encoder of logic gates will translate the comparator outputs to a corresponding digital number.
DETAILS:
In this circuit, I have 10 comparators. Thus, there is a step size of 1/10 the reference voltage. With Vref = 10V, the step resolution is 1V. This translates nicely to the displays. I've marked 9/10, 7/10, 5/10, 3/10 of Vref with waveforms blue, green, orange, red. Note how the output changes when the input voltage passes the thresholds.
Vref also sets the voltage that will give the highest digital number (in this case, 10V).
A huge plus for this type is the instant response, no sample rate, and no clock. The downside is that it is not practical for high bit resolution because of all the comparators required.
