Hi All, i am currently using a voltage divider to bring the voltage down from 140V DC to +5V on the pin of RA0 in a pic micro. My resistors are getting very hot (100W resistors). Is there perhaps another way of measuring 140V DC on a the pin of the micro?
Like this:Use a high resistance voltage divider then use an opamp follower to buffer it to an impedance the PIC A2D likes (around 2k load on opamp output).
This totally goes against the datasheet for minimum input impedance for the input.Use R1 180k and R2 1.2 k. Add 220k series resistor at A/D input.
Microchip Datasheet said:The
maximum recommended impedance for analog
sources is 2.5 kΩ.