I have a circuit that is attempting to measure AC line voltage 120-240V but I was told by the certification test lab that my voltage divider resistors would require an expensive 3 week soak test. The resistor voltage divider is behind a 275V varistor to clamp the voltage, a fuse to protect from short circuits and the voltage is being sent through a high linearity 3750V isolation optocoupler biased by a transformerless mains side power supply so I was thinking that the circuit would meet the isolation requirements. Unfortunately, this does not seem to be the case.

Now I am trying to understand what I can do to create a DC bias to power the optocoupler and how to reduce the voltage to be able to send through the optocoupler since a resistive voltage divider does not seem valid without extensive testing. As a result, I need more information and the test lab seems unwilling or unable to provide this. A reference to the relevant standard as well as any suggestions would be appreciated.

  • \$\begingroup\$ WHo said "soak test"? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 4 '19 at 19:27
  • \$\begingroup\$ @SunnyskyguyEE75 The OP was "told by the test lab". \$\endgroup\$ – Elliot Alderson Mar 4 '19 at 19:30
  • \$\begingroup\$ The soak test is being referenced by the certification test lab. \$\endgroup\$ – Jason K. Mar 4 '19 at 19:35
  • \$\begingroup\$ I meant which Lab? You can do your own Hipot soak test \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 4 '19 at 19:36
  • \$\begingroup\$ Won't mention the lab to avoid any issues. I am in 3 person shop so not really set up to do that according to standards based on requirements of other required testing. You say it is the Hipot soak test? \$\endgroup\$ – Jason K. Mar 4 '19 at 20:11

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