probes? - Page 1
Forum section: electronics / beginners

author: anlsoft
author_rank: Newbie
timestamp: February 04, 2013, 07:48:33 pm
content: How much does the Mhz on a probe mean?What about if you use a 100 Mhz probe on a 50 Mhz oscilloscope.Dave can you make a youtube video about it..

author: Lightages
author_rank: Unknown
timestamp: February 04, 2013, 08:14:21 pm
content: Look up in the stickies above:https://www.eevblog.com/forum/beginners/oscilloscope-training-class-(long)/The 100MHz is the -3db upper frequency point of the probe. It is useful for anything less than that frequency.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: February 04, 2013, 08:19:45 pm
content: I am not the best at answering this but trying to help out ... You can use the leads with no problems but make sure the capacitance is within the range of the leads .. I am using 50mhz leads on my 20mhz scope with zero problems..

author: w2aew
author_rank: Super Contributor
timestamp: February 04, 2013, 09:25:12 pm
content: Quote from: anlsoft on February 04, 2013, 07:48:33 pmAs long as your probe equals or exceeds the rated BW of the scope, you should be OK. The "better" bandwidth rating includes the response of the scope (assuming both are rated for the same BW), so that a 100MHz probe connected to a 100MHz scope will still give you 100MHz response. "Cheaper" probes may rate the BW on the probe alone, so a 100MHz probe connected to a 100MHz scope will give you less than 100MHz of bandwidth.Using a 100MHz probe on a 50MHz scope should certainly ensure that you'll get ~50MHz bandwidth out of it.There are TWO considerations to be careful of:1) Compensation:Make sure you properly compensate your probe. An improperly compensated probe will give you inaccurate readings that will vary based on frequency and signal shape/characteristics. This video discusses 10x probes and proper compensation. You do have to be sure that the probe you use has enough compensation range to cover the input capacitance of your scope:2) If you want to use the probe above a few MHz, you do have topay careful attention to the ground lead length. Here's a video that shows a little about this topic:I hope you find these videos helpful.

author: saturation
author_rank: Super Contributor
timestamp: February 05, 2013, 01:25:49 pm
content: ... and remember its for a sine wave. Other wave forms, such as the common square wave, contain harmonics. A 50 MHz will have its 3rd harmonic at 150 MHz, so it will begin contributing distortion to your waveform as it is rolled off by the probe or the DSO.

author: Unknown
author_rank: Unknown
timestamp: February 05, 2013, 08:15:29 pm
content: The Tektronix document 'ABCs of probes' would be a good read.

author: marshallh
author_rank: Unknown
timestamp: February 05, 2013, 08:36:05 pm
content: http://cds.linear.com/docs/en/application-note/an47fa.pdfEven though it's about amp techniques, the first chapter goes over how you can fail at using a probe.Also in Appendix A is the ABCs of probes by Tektronix.There is another doc similar by Lecroy that covers a bit more quantitatively the relationship of the probe and the scope. I can't find it right now though.