Re: Odd 485 behaviour in ALT and CHOP


If you're trying to trigger on Alt traces, you may have best luck using LF Reject.The trigger circuit sees a low freq square wave with a period of 2X the sweep time.This "signal" is seen by the trigger circuit, in addition to the desired signals & causes erratic triggering.Here is where LF Reject triggering comes in. This is a trigger mode which you will only find on multi-channel scopes.It looks like a low freq signal with faster, smaller (desired) signals riding on the top & bottom levels.The amplitude of the slower signal varies with the vertical position controls, & gets differentiated if the trigger is AC coupled.So, the trigger circuit sees a pretty ratty signal.
LF Reject blocks this slow component.
 HankC, Boston WA1HOS

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