The second video in a mini-series looking into the basics of isolated voltage measurement. Sticking with optical transmission for a second video, we delve into the feasibility of a purely analog system converting voltage to light intensity and back to voltage. We also explore the concept of a closed-loop feedback system which has the potential to greatly improve linearity.
What happens when:
0:00 Introduction
0:14 Analog optocouplers
0:35 DIY optocoupler
2:10 LED and photodiode proportionality
2:45 Input circuit (open loop)
4:32 Rail-to-rail op amps
5:12 Output circuit (open loop)
6:35 Impressive frequency response!
7:12 Linearity (open loop)
7:37 Frequency response (open loop)
8:22 Closed loop feedback topology
8:41 Vishay VOA300 linear optocoupler
9:55 DIY dual photodiode optocoupler
11:07 Adding feedback to the circuit
11:34 Full closed loop circuit
12:52 Looking promising?
13:41 Linearity (closed loop)
14:44 Frequency response (closed loop)
15:17 Comparing analog and PWM optical methods
16:25 Conclusion
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