can any one help me to raise earth resistivity tester circuit voltage to 50 volt

I am talking about the voltage used to measure earth resistivity not the circuit voltage ...

...

I can use a 50 dc volt external power source but the problem when the micro

controller measure the received voltage .... it cannot exceed 5 volt ..

so If I used a 10 mega resistor to drop 50 v to 5 v and 40 v to 4 and so on ...

is this works fine ?? or will cause to get unreal earth resistivity values when use it ??

 

If your micro wont read 50V, then why are you increasing it to 50V, the circuit you posted is a Differential amp with variable gain, not the power supply?

 

Using a voltage divider resistor pair could help but we would need to learn more about your power supply and what the various connections in the differential amp are supposed to do.