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Effect of high voltage line on performance of ADC.

Question asked by on Aug 16, 2015
Latest reply on Aug 21, 2015 by jcolao

Hi every one,,,, 


This is Sudish kumar,


My query is I have an Copper enclosure in that Two PCB boards are there. (1. Power Supply & 2. My CPU Card).

My CPU card will do some dedicated function...


Let me explain it here briefly so that i'll be clear with doubt.


It have Micro controller, RAM, EEPROM, CPLD, 1553 DDC chip, Some relay drivers which will sink some current up on my comand to cpld through RS-422 & 1553 interface by my computer.


1. apart form that i have used Two DAC AD664TD, Two Multiplexer AD526, AD527, One ADC AD1674.


that is for sensing out side analog value & do some further operation up on that input..


I gave 16 analog inputs to 2 multiplexers. ( 8 inputs AD 526 is single ended) & (8 inputs AD 527 is differential ended).


I gave multiplexer output ADC.


ADC output to MICRO CONTROLLER, then i saved that Digital count to my memory.


ex. i gave two inputs of 5v to diff ended mux inputs, i starts observing that input on my computer (i'm reading locations of saved digital data), i made 1 GUI which will give analog input = to digital data of register.


when i contact high voltage line wire of my power supply, the two readings which i'm reading via mux, one is getting vanished.

i dont know reason why, other pins are sensing inputs around 10v  when the high line contacted to body of my enclosure is around is 58v.

reason why i made contact high line to my body to analyze the behavior in heavy EM filed of GHz frequency...!