Help me in Analysing this problem ??

HI All ,

I encountered one problem which m not able to analyze .The Problem goes like this :-
I am Monitoring some signal behaviour and
If i keep Probe of my Tektronix DSO ( DPO2024 ) connected between that signal & reference GND and then switch ON the Main Supply ,my system doesn't switches ON .
And as soon as i remove probe connection from reference ground ,System starts behaving normally . and if again i connect probe to reference ground ( With System in ON Working State ) then i dont face any abnormal behaviour .

In short if i switch ON my main Power supply and then connect probes to monitor required signal ,then there is no problem .
& if i switch ON the main power supply after keeping probes connected then there is a problem .

I would be very thankfull if anyone could guide me in understanding the cause of this misbehaviour .

Regards !!

V V

Hi Vikas,

Sorry If I am spelling your name differently (just guessing that it may be you name).
After reading your problem, It looks to me that its a simple problem of level triggring. Means the chip/circuit in which this signal is transfering may be level capture circuit.

Let me explain in other way...
For every signal when ever its changing the stage from 0->1 or 1->0 then there are 3 stage where a circuit can trigger. Lever trigring (when there is no change in the state), rising edge trigring (when state changes from 0->1) and falling edge trigring (when state changes from 1->0).
Now in you case when power is on and then connect/disconect your probe , then System works properly because it is sensitive to the edge trigring. But when Power is OFF and you connect the Probe, System is not able to detect the rising edge, and that's the reason that when you are going to SWITCH the power , system doesn't start but when you disconnect the probe , it detect the falling edge and start working.

I think above explanation can help you to understand the problem.

Let me know if you need anyother help.

Hi

The prob you are using is overloading your system - try to use a probe with higher impedance who will not over load your signal

All the best

Bobi

I also thought that , but input Impedence of the probe is about 10M Ohm ..... so i dont think that would be any reason for Misbehaviour ...

vikasveshan said:

input Impedence of the probe is about 10M Ohm ..... so i dont think that would be any reason for Misbehaviour

Click to expand...

Then if the input of the probe is 10Megs and unlikely to be causing the switch-on fault, could it be your ground reference proble that inhibits switch-on?
Have you tried switching on with only the 'scope's ground clip connected?