Hp 1741a oscilloscope  - Page 1
Forum section: electronics / general

author: Applemac
author_rank: Regular Contributor
timestamp: February 03, 2019, 01:59:25 pm
content: I seem to be getting an unclear image on my oscilloscope when running a sine wave from my function generator any idea what the issue could be? Its difficult to describe the image moves around on the screen and is shaky.

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 03, 2019, 05:51:15 pm
content: Sorry to maybe ask the obvious, but have you set the trigger mode and threshold appropriately?

author: Applemac
author_rank: Regular Contributor
timestamp: February 03, 2019, 06:37:51 pm
content: Well that is a good question as this is my first function generator and im not sure if I did, im using a hp3314a Function Generator, so just seitched it on pug in the cable to the function out and selected the sine wave.

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 03, 2019, 07:03:11 pm
content: I meant on the scope, and not on the signal generator.After looking at an HP1741 picture - never used one - selecting the "normal" trigger mode (button "AUTO/NORM" pressed) and adjusting the "TRIGGER LEVEL" (rotary button) should do the trick, unless your scope is borked.If it's in auto trigger mode, the signal shown will "jump around" as there is not synchronization between your signal and the scope timebase.

author: tggzzz
author_rank: Super Contributor
timestamp: February 03, 2019, 07:43:56 pm
content: Quote from: Applemac on February 03, 2019, 01:59:25 pmWhat behaviour haschanged? If you have started doing X, then stop it and do something else!If the function generator's frequency is 50Hz, what does the trace look like? Change the frequency up and down a little bit - how does the trace change?With any old scope and "intermittent" behaviour, first check each and every PSU rail to see the DC voltage is correct and the AC ripple is acceptably low.

author: ebastler
author_rank: Super Contributor
timestamp: February 03, 2019, 08:22:43 pm
content: Quote from: Applemac on February 03, 2019, 01:59:25 pmYou could do a bit better in describing the image. Does it move across the screen horizontally only? Does it move up and down? Does the amplitude change?Or post a quick video clip.

author: Applemac
author_rank: Regular Contributor
timestamp: February 07, 2019, 09:46:46 pm
content: Yes your right i did a video but could not post it here so uploaded it to youtube.https://youtu.be/oTndLYrMK_s

author: Applemac
author_rank: Regular Contributor
timestamp: February 10, 2019, 02:38:29 pm
content: It drifts from left to right up and down

author: ebastler
author_rank: Super Contributor
timestamp: February 10, 2019, 03:37:14 pm
content: To me this looks like you "only" have a problem with the vertical. There is some additional signal overlaid on the sine wave. In the faster timebase settings, this also translates into a horizontal wobble -- but probably only because the trigger point changes, due to the added signal.I am not familiar with your particular model of scope; others may have more specific hints. As a general approach, you should first aim to determine whether this problem is in the scope, the signal generator, or the wiring. Some ideas:Does the problem show up on both scope channels, or one of them only? Have you tested the function generator with another scope, and know that it is good? Have you tried different probes or BNC cables to connect the scope to the function generator? Does the vertical wobble also show with the scope's built-in square wave?

author: edavid
author_rank: Super Contributor
timestamp: February 10, 2019, 04:05:52 pm
content: 1. Why did you post this in "Microcontrollers & FPGAs"? It should be in Beginners or Test Equipment.2. It looks like your scope is fine, you just have the HP 3314A sweep turned on. Press the Sweep button to turn it off.(If that doesn't help, post a photo of the HP 3314A front panel.)3. You might want to press the "Preset" button to restore the 3314A to its default state.

author: Applemac
author_rank: Regular Contributor
timestamp: February 10, 2019, 07:22:04 pm
content: The sweep wasnt on and i had already pressed the reset button before doing the video.

author: Applemac
author_rank: Regular Contributor
timestamp: February 10, 2019, 07:26:22 pm
content: Unable to test with another scope as i dont hv one.. yes the wobble appearson all three wave sine, square and triangle. Tried using a probe on tha cal 1v and seems ok on that. Leads me to believe it might be an issue with Hp3314 function generator

author: Applemac
author_rank: Regular Contributor
timestamp: February 16, 2019, 01:17:00 pm
content: Think it was my fault not understanding how to use the oscilloscope properly, as this my first one. Can anyone recommend a good oscilloscope book for beginners please?