|
This circuit is a simplified version of a ramp type digital volt meter (DVM). It can read a voltage up to around 10V with an accuracy of about 100mV. Please allow time for the counters to increment to the correct number.
DVM Series:
Dual Slope Integrating Type DVM https://everycircuit.com/circuit/6675184624599040
Integrator Type DVM (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
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 provides a voltage to be measured. The two left switches act as the voltmeter probes that attach the voltmeter to the voltage source to be measured. The 7-segment displays on the right show the result of the measured value (wait until it counts up to the correct amount).
This example will read a voltage of 5V. If you want to measure a different voltage, stop the simulation, adjust the source on the left, and then restart the simulation.
GENERAL:
The way a ramp type DVM works is to use a ramp voltage (blue waveform) and compare it to the input voltage (orange waveform). During the time when the ramp is below the input, a clock will cause a counter to increment (green waveform). When the ramp exceeds the input, the counter will stop, and the correct value will be displayed.
Basically, a ramp DVM converts a voltage level to a time duration. The higher the voltage, the longer the time the counter increments, and hence, a higher value will be displayed.
DETAILS:
The first opamp is set up as a subtractor. It will give the input voltage to the second opamp comparator. This is where the ramp voltage is compared to the input voltage. The result of the comparison is given to an AND gate. If the result is high (the input is above the ramp), the clock signal is passed to the counter. If the result is low (the ramp is above the input), the clock signal is blocked.
The period the clock is passed = The input voltage / ramp voltage rising rate. In this circuit example, the clock is passed for:
(5V) / (10V per ms) = 0.5 ms.
The clock will increment a counter during this time. The number of clock pulses passed = The time the clock is passed / period of clock. In this example, it is:
0.5 ms / 0.01 ms = 50 clock pulses.
The clock pulses cause the counters to increment to that number. In this case, 50. This translates to 5.0 since every count represents 0.1V.
The second voltage source (red waveform) simulates the sample rate. It resets the counters and theoretically starts the next ramp cycle. In this circuit, it is 1ms.
|
