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I am a student and I am facing a problem with an oscilloscope configuration.

I have two digital outputs coming from two different switches. I want to find the time delay between the operation of these switches. When one switch operates, time starts and then time stops when the 2nd switch operates. For this I am using two channels of a Tektronix oscilloscope.

After studying on net, I came to know that this can be performed by pre-triggering of oscilloscope saying "The oscilloscope is acquiring pretrigger data. All triggers are ignored in this state" what this mean? I don't know how to set the pretrigger for two channels. The time between these two switches is hardly 200 usec.

Can anyone please explain to me, how to do this with an oscilloscope, or any other method, or explain to me the setting of the quoted sentence?

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    \$\begingroup\$ Which model number? \$\endgroup\$ – Brian Carlton Aug 14 '17 at 20:43
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    \$\begingroup\$ What Brian writes, perhaps you should start reading the manual and begin with a simple exercise. Connect the scope's probe to the test signal (the one on the front for calibrating 10:1 probes) and zoom into the rising edge of the wave. Change the (pre)trigger settings and see how that affects the graph. Triggering is usually only done on one channel so using 2 channels makes no difference. Operating an oscilloscope requires practice, so get some by playing with it using a simple test signal. \$\endgroup\$ – Bimpelrekkie Aug 14 '17 at 20:58
  • \$\begingroup\$ Does one switch always indicate the start and the other the stop? You shouldn't need to pre-trigger. What's the scope model? \$\endgroup\$ – uint128_t Aug 14 '17 at 23:55
  • \$\begingroup\$ Model no. TDS210 \$\endgroup\$ – Singing Sparrow Aug 15 '17 at 1:51
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The first few videos in this playlist may come in handy: https://www.youtube.com/playlist?list=PLzHyxysSubUkc5nurngzgkd2ZxJsHdJAb

Basically, you'll want to trigger on the first channel and use cursors to measure the time delay between the switches.

First, put the scope into "normal" acquisition instead of "auto" acquisition mode. Then, set your trigger threshold somewhere between the max and min of your signal (rising/falling edge trigger will be fine). Then, set your time/div setting to have at least 200 usec on screen. Finally, hit the "single" button and wait for your switch to change.

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