testing pi coil with a dso 150 ???

[angleiron]

i have a dso150 and a hantek 6022be the max input voltage on the dso is 50v and on the hantek i think is 5v if i use the x10 probe off the hantek on the dso will the flyback spike from the surf 1.2 pi fry my dso, i have read that the spike is about 250v is that correct, or is there some trick that is used to protect my scope like a gimmick capacitor or something,also is there a variable dampener to find correct resistance tried this one (attachment) but could not get it to stop ringing, it works fine with a 390 ohm there is also one on fast coil tutorial with 2 1.2k resistors and 5k variable but it only ranges from 750ohm to 1k if someone could advise me i would be very grateful.

[6666]

look at preamp out

[waltr]

When I need to look at COIL Kick back I do a 80:1 resistor divider to reduce Voltage to scope probe.

Yes, Coil kickback can be is the hundreds of Volts.

That 'damping' adjust circuit should work. Do you have wire from coil to circuit short?
It is possible that circuit's resistance is not low enough. So put a fixed R (your 390) across coil (on PCB) then connect and tweak the pot. When adjusted to critical damping, remove circuit and measure resistance. Then put a resistor of that value across the one already on the PCB (your 390). I and many of us have more than one resistor paralleled across coil for damping.

The damping adjust is done with scope on Pre-amp output (as 666 said).

[WM6]

i have a hantek 6022be the max input on the hantek i think is 5v if i use the x10 probe off the hantek , i have read that the spike is about 250v is that correct, or is there some trick that is used to protect my scope like a gimmick capacitor or something,also is there a variable dampener to find correct resistance tried this one (attachment) but could not get it to stop ringing, it works fine with a 390 ohm there is also one on fast coil tutorial with 2 1.2k resistors and 5k variable but it only ranges from 750ohm to 1k if someone could advise me i would be very grateful.

This is your scope input hardware:



Read this part of 6022be debate to clear your dilemma:

https://www.eevblog.com/forum/testge...z-usb-dso/125/

Using original parts fly-back voltage is probably inside 150V, but it depends
on coils, used power TR, power supply, TR driving .... so 10x probe should be used.

[angleiron]

hi, thanks for all of your replies i have taken the dampening resistor off the pcb and put it in the search head it works fine a pre decimal 2 shilling at 12/13 inches,had another look at the variable resistor ,duff preset, thats what you get for not checking before soldering, i have downloaded instructions for the 6022be it says gain range does that mean min to max voltage with probe settings many thanks for your advice looking forward to your reply.