How should I se tup oscilloscope to measure different waves? - Page 1
Forum section: electronics / beginners

author: Jasonbit
author_rank: Regular Contributor
timestamp: September 08, 2018, 05:41:50 pm
content: Hello folks,I am trying measure/view a wave signal on oscilloscope through this circuit:https://s15.postimg.cc/xmku1yzjv/photo1.pngIf I only use a probe I can measure a different waves (two connectors are good, I tested individual and I can see a different waves signal). But If I connect the second probe I receive this result:https://s15.postimg.cc/al48w9xcb/photo2.pngI think some equipment configuration is missing...but what could it be?ThanksAlso I tried do this circuit with bridge rectifier but the result it is the same. This is a circuit:https://s15.postimg.cc/5qf5bhw1n/image1.pngOnly connect a yellow probe:https://s15.postimg.cc/j7c3uiyp7/image2.pngAfter connect the second probe (blue):https://s15.postimg.cc/cgvml46ej/image3.png

author: james_s
author_rank: Super Contributor
timestamp: September 08, 2018, 06:13:31 pm
content: What are you expecting to see?I can't easily tell from the picture but it looks like your scope probes are grounded in different places? Keep in mind the ground on one probe is electrically connected to the ground of the other probe so if you connect them to different nodes in the circuit you are connecting those nodes together.

author: StillTrying
author_rank: Super Contributor
timestamp: September 08, 2018, 06:15:03 pm
content: The GND clips of both probes have to be connected to exactly the same voltage, usually ground or 0V, you're shorting out the bridge through the scopes GND clips.One way to see both waveforms is to use just one channel and save the waveform on screen, then move both the GND clip and probe to the other side of the bridge. That's what I did for a bridge rectifier here, some time ago!https://www.eevblog.com/forum/beginners/fwb-full-wave-bridge-rectify/msg1117268/#msg1117268

author: Benta
author_rank: Super Contributor
timestamp: September 08, 2018, 06:37:08 pm
content: Unless you knowexactlywhat you are doing, never use more than one probe with ground clip. The other probe(s) should only have the tip(s) connected to whatever you're measuring.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: September 08, 2018, 07:48:46 pm
content: To see Full Wave Bridge rectification properly on the Rigol you need to use Differential Probing and the Math channel.

author: Zero999
author_rank: Super Contributor
timestamp: September 08, 2018, 08:50:36 pm
content: Quote from: Jasonbit on September 08, 2018, 05:41:50 pmYou've short circuited one of the diodes, so this is exactly what you should expect to happen. This is a very common beginner mistake. The 0V on each 'scope probe is connected to the others. If you leave it connected up for too long something bad will happen. The transformer, rectifier or oscilloscope/probes will pass too much current and overheat.Here's an equivalent circuit of what you have with the 0V of one probe connected to the output of the rectifier and the other to the input.As mentioned above, use two probes with the commons connected to the same point and the differential function.

author: JS
author_rank: Frequent Contributor
timestamp: September 09, 2018, 01:15:37 am
content: https://www.youtube.com/watch?v=xaELqAo4kkQ&frags=pl%2CwnOne of the most quoted videos in the forum, yet people get away missing it.JS