Q:

Opto-isolation amplifier giving no output

First of all, thanks to the community for having such helpful answers here - don't post very often but here's one I could really do some help with.
I want to measure a voltage range of 0-100V DC in an isolated manner and using an Arduino Uno. I've got a HCPL 7520 (datasheet) and created an initial test circuit with just 5V input but I'm getting no output. I've got a voltage divider to bring the 5V down to the +/- 200mV range and chosen resistors to bring the current to ~10mA (which is less than the 20mA max).
But whenever I measure voltage between VOut and Vdd2_Gnd, I get 0V. I'm no expert so any advice would be much, much appreciated !

A:

You've got \$V_{REF}\$ tied to 0 volts - the recommended value is between 4 volts and \$V_{DD2}\$: -

The whole premise for this device amplifying is that it has a gain determined by: -
$$\boxed{\dfrac{V_{REF}}{0.512}}$$

