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How can I measure video-to-video delay using the VM700T?

Question :

How can I measure video-to-video delay using the VM700T?

Answer :

There is a way to measure video-to-video delay with the VM700T. It is a manual process but the instrument will provide you with a numerical result. To measure video delay please follow these steps:

1) Connect the delayed signal to input A, B or C.

2) Connect a clean, delay-free (direct from generator) copy of the signal to the external sync input.

3) In the waveform mode, press the menu button and set the sync to either match the input you're using (A, B or C) or set it to "Lock to Source".

4) For small delay values the default zoom level should be sufficient but for larger delays I would recommend zooming out as much as possible. To do this, make sure the Move/Expand and Left/Right/Up/Down buttons near the general purpose knob are set to expand and left/right respectively. Then touch the middle of the screen and hold your finger there, while holding this point spin the general purpose knob counter-clockwise until you cannot zoom out any further, this should display about 20 lines on the screen simultaneously. This will be most obvious on black burst signals.

5) Find the portion of the waveform marked line 1, field 1 and use the left cursor (Menu button, select cursors) to mark the sync point for this line. Remember what this portion of the waveform looks like (this should be easy as it is the beginning of the vertical blanking interval and therefore has a unique look to it).

6) Switch the sync source to the external sync input. This will cause your waveform to be shifted left/right by the amount of delay in your signal.

7) Scroll the display until you find the vertical blanking you found in step 5. In the case of an 11ms delay, this is about 170 lines (9 screen widths) to the right so it may take quite a bit of scrolling.

8) Once you find this point, use the right cursor to mark it.

9) At the bottom of the cursor display there should now be a readout labeled "Time from L to R:" on the second line from the bottom on the left side of the screen. This will be the measured distance between the two cursors in microseconds (about 11,000 for 11ms delay).

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FAQ ID 63476

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