Basic Scope Q: Auto vs Normal trigger

[LanceM]

Learning on an older 2 chan 20 MHz analog scope (of questionable
condition), using mostly for automotive t-shooting

Shouldn't I be able to use the Normal trigger setting to get a steady
signal off a 12 V battery? I can get a brief glimmer as I rotate the
trigger level, but can't maintain the trace

No problem/steady trace using the Auto trigger


Thank you,
Lance

 

[Kevin Carney]

Use normal trigger for a low speed signal (less than approxiamately 60 hz).
Auto trigger will sweep after every sweep. Normal will only sweep when it is
triggered (by the input signal). When you apply dc voltage to the input and
turn the level control, the scope will sweep whenever the level control
(being turned by you) crosses the level of the dc voltage applied. That last
sentence was a mouthful ! Hope you understand.

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[Jim Adney]

Learning on an older 2 chan 20 MHz analog scope (of questionable
condition), using mostly for automotive t-shooting

Shouldn't I be able to use the Normal trigger setting to get a steady
signal off a 12 V battery? I can get a brief glimmer as I rotate the
trigger level, but can't maintain the trace

No problem/steady trace using the Auto trigger

No, you're seeing exactly the right thing.

Normal trigger waits for a trigger event to start a sweep.

Automatic trigger will wait for a trigger event only a certain amount
of time, which depends on the sweep speed. If no trigger event arrives
within this time period, the sweep will trigger "automatically" and
then start the waiting period again.

Since you're watching a DC signal there is no trigger event so under
Normal Trigger it will just wait forever, and you see nothing.

Both modes have their useful moments, but it's important to understand
the difference between them.

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