50Hz when you touch Oscilloscope probe

[mvs sarma]

this problem is prevelent even with 74 series . a cct rigged up on a prototype had misarably failed due to noice pick-up. perhaps with proper precautions towards poer decoupling at each IC and by keeping poer extention boards, etc away from the project prototype, and by sticking the specific metal sheet supplied with the bread board, beneath and keeping at earth potential, we may suceed in preventing the power pickup problems.  all of us are aware of antisattic wrist straps with earthing cwire etc . these are to be specifically used when working CMOS digital ICs and in locations of low relative humidity.              (  B series, now a days are ruggedized by protection diodes across every pin  to prevent failure, induction is stil a problem) . whether one measures 50/60Hz or a hormonic depends perhaps on the amount of induction and amount of noice generated by devices adopting triac conrollers- even after all the reglations reg power purity.

hope with adequate precautions one could still prototype and test on bredboards.
anxious to track the success of test rig ups.

sarma

 

[aartak]

Inside Your Scope there are two capacitors vith value about 10nF connected between Mains lines and case of Scope for filtering purposes. they Create some AC voltage on Scope Common. Scope Shows voltage between common and probe. When You tuch probe You ground it by Your Body capacitance so voltage difference is created. To avoid this simply ground the scope common.Scope must have spetial coonnector for Grounding

 

[mvs sarma]

you are right aartak.

it is a good paractice to earth ant test equipment before it is used. the problem wont be there and it cultivate a healthy habbit.

Nice

sarma