Oscilloscope probe compensation problem  - Page 1
Forum section: electronics / beginners

author: TomThaMan
author_rank: Contributor
timestamp: February 03, 2015, 10:25:14 pm
content: Hi all,First post here! I'm from the Netherlands, just bought my first scope. I'ts a Tektronix TDS 320. Started to play around with it a little, but soon stumbled upon the following problem. When I try to do a probe compensation, I do not get a square wave signal from the scope. Its a triangle wave form. Tried to search on the forum but found nothing. Any suggestions on what could be wrong?Many thanks.Tom

author: Lightages
author_rank: Unknown
timestamp: February 03, 2015, 10:31:28 pm
content: Do you have the input coupling on your scope set to AC or DC? It should be set to DC. Is this problem with only one probe or do you have two and the problem is with both? If it is with just one then perhaps you have a broken probe.It is also possible that you have a broken scope.

author: w2aew
author_rank: Super Contributor
timestamp: February 03, 2015, 10:54:49 pm
content: Also check three things:Some scopes will adjust the frequency of the cal signal with the time/div. Set the time/div to about 1ms/div.Make sure the probe is in the 10x position - there is no compensation adjustment for 1x since that is ONLY for low frequency work.Use DC coupling on the scope.

author: TomThaMan
author_rank: Contributor
timestamp: February 03, 2015, 11:24:38 pm
content: Thanks for the quick reply's!And w2aew, I love watching your videos! Keep up the fantastic work, greatly appreciated!Scope is to DC coupling, probes are tek p6109, wich are 10x only (?)The scope auto adjusts the signal to 500 microseconds, but if I manually set it to 1 millisecond it's still the same.Got a friend with a scope as well, would it be a good idea measuring the output of my scope comp with his scope?

author: tautech
author_rank: Super Contributor
timestamp: February 03, 2015, 11:44:58 pm
content: Quote from: TomThaMan on February 03, 2015, 11:24:38 pmYour image shows ~100 mV pp triangle waveform riding on a +200 mV offset.This is nothing like a Cal waveform should be.What is the p-p spec for that Tek?Have you another signal source to verify the scope inputs or probe is not the problem?Yes you might want to check the Cal output with another scope or even a DMM on AC that should return a reading of ~ 1/2 the rated Cal pp voltage

author: TomThaMan
author_rank: Contributor
timestamp: February 04, 2015, 07:49:02 am
content: Quote from: tautech on February 03, 2015, 11:44:58 pmThe rated voltage is 5v, and my multimeter (87v) returns 450mv AC that is gradually dropping to about 350 mV. On DC it says 2.25 (also dropping a bit) volts.

author: tautech
author_rank: Super Contributor
timestamp: February 04, 2015, 09:48:23 am
content: Quote from: TomThaMan on February 04, 2015, 07:49:02 amSomething doesn't add up.I think for a sanity check you should visit your friend to check the Cal output and also check your scope use techniques.There is much to learn as this is your first scope and you will find an experienced user as a mate a great asset.Also hunt out the sticky thread in "beginners" by memberw2aewand Daves video's.Have you got the manual? Service or User?Come back to us with your findings.

author: jpb
author_rank: Super Contributor
timestamp: February 04, 2015, 11:29:07 am
content: To test your cal output a simple wire should be sufficient, I tried this with my scope - see attached photo - and though it is noisy you can clearly see the square wave.