Using TEK 2440 Scope To Capture A Pulse - Page 1
Forum section: electronics / testgear

author: George_Race
author_rank: Regular Contributor
timestamp: August 31, 2014, 07:11:41 pm
content: I am still learning how to use the TEX 2440 Digital scope, and need some help and direction.I am trying to capture a 5 volt digital pulse that is .01 mS wide that only occurs once every second. I can see it on my analog scope, but it would be nice to learn how to capture and save it for further observation on the TEK 2440.This pulse is the 1 second pulse coming from my Trimble 10Mhz GPS Disciplined Oscillator that I use as the primary standard for my sig gen, freq counter, and spectrum analyzer.I think I am making this far too hard to do. After about an hour of trying, I finally am giving up and seeking advice!Can someone please give me the setup steps to make this happen, using the TEK 2440?Thanks.....George

author: tautech
author_rank: Super Contributor
timestamp: August 31, 2014, 08:48:15 pm
content: Will a Tek 2240 not let you set the trigger for a "Single" event?

author: larry42
author_rank: Regular Contributor
timestamp: August 31, 2014, 10:21:28 pm
content: Check Single seq acq mode? though most scopes have 'Normal' mode for this...

author: iDevice
author_rank: Regular Contributor
timestamp: August 31, 2014, 10:34:55 pm
content: One of the very current mistakes is to stay in auto sync mode for low speed sweeps.The scope goes automatically in it's free run sweep mode which is unrelated to the input signal when the trigger rate goes under the threshold.A 1 sec rate is below so it applies here.So you have to be in "normal" so that the time base sweeps only when it receive a trigger.If you want to lock the shot in memory, you can also use the "single" mode so that the scope won't re-trigger until you re-arm it by pushing the "acquire" button.You also have to check that your trigger level is set correctly to actually get one depending on the input signal.I just took a picture of what you should get if trigger level and trigger mode are correctly set.I reproduced your signal with my arb gen: one 0,01ms pulse every sec.Note that because the pulse is a positive +5V TTL pulse, the trigger level is set at 50%, +2,5V.Hope this helps.

author: George_Race
author_rank: Regular Contributor
timestamp: September 01, 2014, 12:18:28 am
content: Looks like a great solution, that pulse really is well defined!Thanks, I will give it a try in the morning.George

author: David Hess
author_rank: Super Contributor
timestamp: September 01, 2014, 01:39:03 am
content: This is easy on a 2440 or any of that series of DSOs.Like iDevice says, you need to use normal mode instead of auto or auto level. Then the acquisition will only occur when a trigger is detected. You will have to adjust the trigger level manually.When I made the same measurement on a GPS pulse per second output on my 2230 which can operate in analog or digital storage mode, the first indication that the pulse was occurring was the trigger indicator blinking once per second. In analog mode it was actually possible to view the event with the room lights dimmed and the intensity turned up but of course digital storage mode is much easier on the eyes.

author: George_Race
author_rank: Regular Contributor
timestamp: September 01, 2014, 02:22:35 pm
content: Like everything in life, it is very easy when you know what to do!I set the trigger mode to Normal, and as I adjusted the trigger level the pulse just appeared on the screen and sets there refreshing every second. Very neat!Does anyone know of a simple and down to earth, easy to follow and understand, how to use a TED Digital Scope article? I have the full users manual but the more I read the more I don't understand!Thanks guys for the quick response and great help,GeorgeHere is a screen shot of how it looks!http://www.mrrace.com/ebaypictures/Trimble%201%20sec%20Pulse.jpg

author: David Hess
author_rank: Super Contributor
timestamp: September 01, 2014, 04:38:37 pm
content: Quote from: tautech on August 31, 2014, 08:48:15 pmThe Tektronix 2440 can absolutely trigger on and acquire a single event.Further if you are in repetitive (equivalent time sampling), envelope, or average mode, then single shot acquisition mode will execute multiple acquisitions to fulfill the requirements and then stop displaying the number of acquisitions performed. Repetitive mode combines with sample, envelope, and average mode.

author: David Hess
author_rank: Super Contributor
timestamp: September 01, 2014, 04:51:14 pm
content: Quote from: George_Race on September 01, 2014, 02:22:35 pmI think Tektronix published some application notes covering the operation of the 2440 series but offhand I cannot point them out. The 2440 Operations Manual is about as good as it gets despite its density.Part of the problem is some of the terms and functions discussed like Delta Delay Time are going to be foreign to user of modern DSOs because they originated in high end analog oscilloscopes.I never really understood Delta Delay Time until I got an analog oscilloscope which supported it. Now I find it difficult to live without even if I do not immediately need it although modern DSOs generally have some type of difficult to use equivalent.

author: George_Race
author_rank: Regular Contributor
timestamp: September 03, 2014, 06:51:01 pm
content: Hi David, yes I did find some TEK App Notes that delt with the 2440. But they are very much like the User Manual.I decided to put my nose in the manual, one section at a time setting up and making the examples work. Have done that a bit and it is slowly making more sense. My problem seems to be that if I don't use it frequently, I forget what button to push to make things happen.I have put together a group of PRGM presets, so now I can just punch up what best applies to what I am trying to examine with the probe. That seems to be the best way I can get around the confusion I still have for the digital scope.Unlike the analogue, you cant just "probe" and just spin the Volts/Div and Time/Div and have something come on screen that represents the signal.That seems to be the biggest hump to get over, but I am learning.Thanks to all for the comments, appreciated.George

author: David Hess
author_rank: Super Contributor
timestamp: September 03, 2014, 10:28:01 pm
content: Quote from: George_Race on September 03, 2014, 06:51:01 pmOddly enough, the 2440 is the oscilloscope I use when I want to do one handed probing and am not sure what I am looking for.If you use a probe that supports the identify function, then you can set the identify function to do all kinds of useful things like Autoset.

author: George_Race
author_rank: Regular Contributor
timestamp: September 03, 2014, 11:31:43 pm
content: Hi David, I have no idea what identify function is, or what Autoset does.Into the manual for some more information!George