Oscilloscope and capacitors.

[stk2008]

Hi all as some of you may remember I have an Oscilloscope its a tek 2205 20Mhz.

I was trying to learn how to test the discharge time of a capacitor but unlike on a digital scope I cant keep the trace on screen to see when I pressed the button to charge to when I releases it to watch the capacitor discharge.

I think I can only do this with a storage scope?.

Thanks

 

[ericgibbs]

hi,
A bit fiddly, but you could use a 555 or another simple timer to pulse a relay.

The relay contacts would charge the cap and also externally trigger the scope.

 

[stk2008]

Ah I see to get a repetitive trace then I could see the trace through out the cycle.

 

[crutschow]

Do you have the oscilloscope in the NORM trigger mode not the AUTOMATIC Mode, with DC trigger coupling and minus slope? In the NORM mode you can adjust the trigger level so that it will only trigger at start of the discharge.

 

[stk2008]

Nope I had it set to AUTO I will give what you say a go when I next get free in me workshop (problems with having kids and a better half I suppose hahahahaha).

Thanks