# DSO Screen Refresh - Start position

I just picked up my first DSO Oscilloscope, A Siglent SDS1052DL. I have never used an Oscilloscope, so I am trying to learn the basics. I have the following square wave, which drifts during the screen refresh. I know there is a way to set the start position but I can't find it in the scopes directions. I may not be looking in the correct place for it either. Is this called the Video Trigger? If not, what is it called and perhaps some hints on how I can set it?

• The word you're looking for is "trigger". You set the the right kind of trigger on the channel you're using - there's usually different kinds of trigger. You want a simple rising edge, or falling edge, trigger. – Majenko Dec 31 '14 at 0:02
• Also, set the trigger source to the channel you want to trigger on - for your photo that would be channel 1 - and set the trigger level somewhere within the signal range. Once the trigger source is set correctly, and the trigger level is within the voltage range shown on the screen, there should be an icon showing the trigger level on one side of the screen. – Peter Bennett Dec 31 '14 at 0:15
• Thanks - Took me a few tries, but I got it. Make it answer and I'll check it – PhillyNJ Dec 31 '14 at 1:03

The word you are looking for is "trigger". The trigger system on a scope can seem fairly complex to a beginner. The trigger system has several controls:

Trigger source: Channel 1, Channel 2, External, Line (AC power line)

Trigger mode: Auto (sweeps runs without a trigger of none available), Normal (sweep only with trigger), Single Sweep (run once on trigger, must be reset for another sweep)

Trigger type: rising edge, falling edge, TV (Analog TV sync)

Trigger Level: a pot to set the voltage at which a trigger occurs.

Usually, on digital scopes, an icon will appear on one side of the screen to indicate the trigger level.

Digital scopes may allow you to set the trigger point to be near the left or right side of the screen, or in the center (pre-trigger or post-trigger).