Oscilloscope settings - Page 1
Forum section: electronics / beginners

author: airofu
author_rank: Newbie
timestamp: December 24, 2019, 12:12:26 am
content: Very new to using an Oscilloscope but I have a DSO138, I think I've got it working how I want but not sure if the DSO138 is my limitation or the probes...I'm trying to set my amp gains and checking for a clipped signal at 40hz. At low gain around it is around 40v and it shows the signal as normal (1v-x5 setting), I keep raising the gain but it seems to go beyond the screen (past 60v max? tried changing the scale but it seems to go too high to show the signal). Do I need a higher spec Oscilloscope maybe DSO150? or can I change the probes to x10 and this should show me the higher voltage/signal? Hope that makes sense or I could be totally off-track....

author: ataradov
author_rank: Super Contributor
timestamp: December 24, 2019, 12:24:30 am
content: Quote from the official spec: "Maximum Input voltage: 50Vpk"And yes, 10x probe will help you here.

author: airofu
author_rank: Newbie
timestamp: December 24, 2019, 08:01:23 am
content: Thanks for confirming, will get some x10 probes and see how I go.

author: tggzzz
author_rank: Super Contributor
timestamp: December 24, 2019, 08:45:36 am
content: If you are using the scope to measure mains, stop right now before you damage the scope or yourself.Understanding and correctly using probes is vital to being able to use a scope. You would benefit from reading the references (particularly the safety references) inhttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: magic
author_rank: Super Contributor
timestamp: December 24, 2019, 09:04:48 am
content: For 40Hz you might as well use a divider made of two resistors. Even for 40kHz if they are reasonably low value like 100k/10k, but that's about the limit.Which isn't to say that a 10x probe isn't a useful thing anyway, and not just because of increased input range. Much lower input capacitance too.

author: airofu
author_rank: Newbie
timestamp: December 24, 2019, 09:34:06 am
content: I'm measuring a 40hz sine wave on my car amp checking for clipping....hoping the x10 probes will give me more range to see the signal.

author: tggzzz
author_rank: Super Contributor
timestamp: December 24, 2019, 10:08:14 am
content: Quote from: airofu on December 24, 2019, 09:34:06 amOK.Knowing the purpose allows more useful responses without wasting time; e.g.https://entertaininghacks.wordpress.com/library-2/good-questions-pique-our-interest-and-dont-waste-our-time-2/

author: Psi
author_rank: Super Contributor
timestamp: December 24, 2019, 10:21:00 am
content: My DSO138 came with some direct connect BNC clips, not a proper probe with built in resistor/cap.So i'm not sure exactly how 'supported' proper probes are with the DSO138.I just put a proper 10x probe on mine and it did seem to work. 30V = 3 div.but your millage may vary.

author: magic
author_rank: Super Contributor
timestamp: December 25, 2019, 10:01:40 am
content: Does it have compensation signal output? Uncompensated 10 Meg probe will be worse than uncompensated resistive divider.Seriously, OP, just use 10k/100k resistor to divide the output and multiply what you see on the screen by 11x. Alternatively, make 90k out of 68k+22k for exact 10x division ratio.There is nothing wrong with 10x probe, but you will need some (typically 1kHz) square wave signal to adjust the probe before using it.Quote from: tggzzz on December 24, 2019, 10:08:14 amMaybe read the OP

author: tooki
author_rank: Super Contributor
timestamp: December 25, 2019, 11:28:55 am
content: Quote from: magic on December 25, 2019, 10:01:40 amYes, it does. I think I tried a 10x probe on my DSO138 way back when and it worked fine.

author: tggzzz
author_rank: Super Contributor
timestamp: December 25, 2019, 08:49:24 pm
content: Quote from: magic on December 25, 2019, 10:01:40 amLet's add the bit you chose to omit, i.e.Quote from: airofu on December 24, 2019, 09:34:06 amThe OP did not mention car amplifiers. The OP did not mention a maximum voltage that was to be measured:Quote from: airofu on December 24, 2019, 12:12:26 am

author: Gyro
author_rank: Super Contributor
timestamp: December 25, 2019, 09:47:04 pm
content: Quote from: tggzzz on December 25, 2019, 08:49:24 pm^^^^ Somebody had a crappy Christmas Day then!(Or is still suffering the after effects!)