Sounds like a fun tool to have in a workshop
My question is, would one clamp that input signal back to the negative side of the voltage divider or to battery neg. The voltage divider does not share negative with the battery in my circuit.
It is. It is like a miniature taser, sparks and everything. You apply it to the outside of a box at everything you can see sticking out. So that is socket ends on all connectors, plugs and even through ventilation holes and slots. The box under test is on a table standing on a huge sheet of aluminium, surrounded by a large space, barriers and traffic cones, and warning signs.
400:1 means you're measuring >1000volt?Give us the full picture.Forget about zener diodes.You could use a 2-stage voltage divider, and clamp to the unregulated supply (5volt, 12volt) of that 3.3volt processor, with normal diodes. That would take care of positive spikes, negative voltage, even when the Arduino is off (unlike a zener).Leo..
I calculate 1/32 watt for a 10Megohm resistor with 600volt across.600*600/10000000= 0.036watt. Not a problem for a single resistor.Common resistors shouldn't have more than 100-200volt across.Use at least four in series, and more if you're expecting high spikes.Leo..
I'm sure an L358 won't be happy with 1000volt on it's inputs...Better use some clip-on hall sensor there.+1 for the neatly drawn diagram though.Leo..Edit: A trinket has a 3.3volt processor, so I2C pull up should go to 3.3volt, not to 5volt.
The L358 isnt seeing 1000 volts its on a shunt resistor and should be around 75mV max at normal conditions.and for the CR1 and CR2 i was aiming for safety