Rigol DG1022 Vpp problems - Page 1
Forum section: electronics / beginners

author: ticktock3t
author_rank: Contributor
timestamp: December 04, 2012, 04:59:03 am
content: I recently got a new Rigol DG1022 and when I was playing with it I noticed something strange when setting Vpp. When I would set the Vpp to say around 2v I would get a Vpp of 4v on my oscilloscope. After a while of trying to figure it out by going through menus with no luck it started working properly again. Any one else have this problem.

author: Bored@Work
author_rank: Super Contributor
timestamp: December 04, 2012, 06:18:00 am
content: It is not a problem, you didn't terminate the output with 50 Ohms.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 04, 2012, 07:31:39 am
content: the dg1022 is setup for 50ohm output (check again in your menu) but eventually the OP didnt terminate it so. the problem is he failed to realize it in his earlier threadhttps://www.eevblog.com/forum/beginners/rigol-dg1022-square-wave-issues/?topicseenwhere 6 times people adviced for terminated line.

author: BravoV
author_rank: Super Contributor
timestamp: December 04, 2012, 08:17:02 am
content: Quote from: Mechatrommer on December 04, 2012, 07:31:39 amIts funny how the op keeps ignoring those questions/comments at his other thread regarding the critical connection needed for the measurement, while keep whining on how the he keeps getting crappy signal, probably he is using the saliva wetted, slightly conductive and used (yuck) dental floss for the connection, go figure.

author: ticktock3t
author_rank: Contributor
timestamp: December 04, 2012, 07:14:49 pm
content: How would I terminate the 50ohm output?

author: robrenz
author_rank: Super Contributor
timestamp: December 04, 2012, 07:21:42 pm
content: Either ainline50 ohm termination or a bnc tee with a regular 50 ohm termination on one leg. In either case they get attached to the scope input and then plug your 50 ohm bnc cable from your FG into the termination.

author: robrenz
author_rank: Super Contributor
timestamp: December 04, 2012, 07:46:48 pm
content: Explanation of why fromthis thread

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 04, 2012, 08:07:49 pm
content: Quote from: ticktock3t on December 04, 2012, 07:14:49 pmif you havent figure that out... the 101 dummy guide is to connect a 50 ohm resistor from signal wire to ground (usually shield of coax wire) near the scope input end. i also suggest for you to google why and what is the 50 ohm characteristic impedance transmission line and 50 ohm termination. w2aew video also usefull to get the idea of reflection if not using proper terminated line...

author: robrenz
author_rank: Super Contributor
timestamp: December 04, 2012, 09:15:26 pm
content: The OP needs to get the simplevoltage divideraspect of Impedance matching first. I had a hard time getting this very simple concept in the beginning also.When set for 1V the FG actually outputs 2V into its internal 50 ohm output resistor (50 ohm output impedance). It does this because it expects the instrument it is driving to have 50 ohm input impedance (a 50 ohm resistor to ground internally) this forms a 2:1 voltage divider and the driven instrument sees 1V.The added 50 ohm termination is in parallel with the scope 1meg input resistor and that gives 49.9975 ohms input impedance that is very close to what the FG is expecting.