attenuator max input

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attenuator max input

Post by astuntas » Wed Feb 19, 2014 6:45 am

I have just purchased a standard kit, which has 4 attenuators 1:20. There is a warning on each of them "max voltage 300V". One of main uses of these attenuators would be ignition primary, which can easily have spikes up to 400V. I am worried not to cook the attenuators measuring this ignition primary, and in case this may happen - cooking the scope input due to over-voltage (giving the direct 400 V spike to scope instead of 20 which the attenuator would produce). On the other hand, I've seen so much manuals from different sources, with people using these attenuators for ignition - without worrying to damage anything.
I would appreciate your comments on this case. Thank you !

Steve Smith
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Re: attenuator max input

Post by Steve Smith » Thu Mar 13, 2014 10:40 am

Hello and thanks for the enquiry, sorry my reply is late
This is an interesting point you have raised on one I have researched regarding the stated maximum input voltage of the attenuator.
There is no doubt, as you have mentioned, that the ignition primary voltage can peak as high as 400v+.
When zooming and measuring in on the ignition spike attached we can see that the maximum stated input voltage is exceeded by 64 volts for only 3.4 micro seconds, which again is typical of an ignition spike.
The stated maximum input voltage of the attenuators is 300v, however they are tested beyond this value to ensure the integrity of the attenuator whilst operating continually at 300v.
Given the very short time frame we exceed the 300v value and the inbuilt protection both within the attenuator and scope there are no issues surrounding damage to either component or more importantly the end user.
I hope this helps…….Take care……..Steve

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