| Electronics > Beginners |
| The horizontal line on oscilloscope display |
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| gkmaia:
While the scope is not receiving any signal it displays a straight horizontal line. Is this line what is referred as blanking? If it is not it. What does the blanking circuit of an ocilloscope outputs to the crt? And what are simptoms of a faulty blanking circuit? What block of the scope circuit has failed when there is no horizontal straight line while it is not receiving signals? |
| tggzzz:
--- Quote from: gkmaia on April 20, 2019, 09:10:11 am ---While the scope is not receiving any signal it displays a straight horizontal line. Is this line what is referred as blanking? If it is not it. What does the blanking circuit of an ocilloscope outputs to the crt? And what are simptoms of a faulty blanking circuit? --- End quote --- The scope displays the voltage at its input. If the input is constant, then the trace is a horizontal line. Blanking refers to turning off the beam when it is "flying back" from the right hand side of the screen to the left hand side, and optionally to turning the beam off before the a sweep is triggered. Experiment with the "norm" triggering mode and with slow sweep speeds. |
| gkmaia:
Thanks for your answer. Blanking makes sense now. I understand if I am scoping a 5v dc signal it will display a straight line. My scope does that fine. But I do not see a straight flat line when not scoping any signal or when on GROUND coupling and it is not because the vertical position is off the screen or vertical V is out of range. What block of the scope is possibly faulty in a case like this? Horizontal amp? Sweep? Blanking? Trigger? |
| StillTrying:
"But i do not see a straight flat line when not scoping any signal or when on gnd coupling." Is trigger set to AUTO. |
| tggzzz:
--- Quote from: gkmaia on April 20, 2019, 09:34:05 am ---Thanks for your answer. Blanking makes sense now. I understand if I am scoping a 5v dc signal it will display a straight line. My scope does that fine. But I do not see a straight flat line when not scoping any signal or when on GROUND coupling and it is not because the vertical position is off the screen or vertical V is out of range. What block of the scope is possibly faulty in a case like this? Horizontal amp? Sweep? Blanking? Trigger? --- End quote --- Before thinking that the scope may be faulty, assume that you haven't set the controls appropriately! You need to do some research into a scope's basic controls. There are many such tutorials available, one is Be very aware of the safety hazards when using scopes, and use the correct type of probe. For pointers, see https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/ |
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