I am making a voltage divider with four 1M 1206 thick-film resistors and a single 2.7k resistor. The input to this voltage divider will be mains line and neutral.
I want to measure the voltage at line with respect to neutral, with the nominal voltage being 240 V +/- 1%.
I also want to protect this circuit against lightning surges. For that purpose, I am using four resistors in series to deal with high voltages, something like this circuit:
I can't decide which type of resistors I should use. Should it be general-purpose resistors, high-voltage resistors or anti-surge resistors?
I have seen similar units fail in the field due to lighting surges, with the burning of resistors and PCB traces in that section.
- Would adding MOVs at input be useful also?
- Does the PCB layout matter much in this section?
- Any other protection device that I should consider?
- How should I select rating of my high-voltage/anti-surge resistors to protect against lightning?