Hi

I have to measure the Earth resistance and it will be sense by microcontroller and if it will be too high power have to be shut down . I have Line Neutral and Earth . What can be the smallest ckt to measure the Earth resistance?

 

You may want to read Principles and testing methods of earth ground resistance and better describe your objective and how you plan to go about it. What is Lione Voltage? Would Earth and Neutral be bonded and what resistances you anticipate or would be in your defined limits.

Ron

 

Check out Mike Holt's site and Utube video's he gives a few examples of measuring earth conductance..
Max.

 

if it is relative measurement, you will need
1. a microcontroller can do high resolution ADC (16 bit or above)
2. two 1k ohm 0.1% resistors: each is in series with ADC pin for measuring neutral or earth impedance.

 

if it is relative measurement, you will need
1. a microcontroller can do high resolution ADC (16 bit or above)
2. two 1k ohm 0.1% resistors: each is in series with ADC pin for measuring neutral or earth impedance.

That sounds oddly specific. Just those three parts and nothing else?

 

As others have said, there is a lot to consider when performing this measurement. If you google for the term "earth/ground measurement guide" you will find several useful guides from Fluke, Chauvin Arnoux, etc that will certainly help you narrow your problem proposition.

 

That sounds oddly specific. Just those three parts and nothing else?

If TS wants to measure soil conductivity I can beat that with one microcontroller and one capacitor.

I don't think TS is measuring soil conductivity. TS wants to measure resistance between mains NEUTRAL and EARTH BOND.
What happens if what you think is NEUTRAL is not NEUTRAL and is in fact LINE?

 

What happens if what you think is NEUTRAL is not NEUTRAL and is in fact LINE?

Uh, a shocking episode in life is a possibility?

Ron