Embedded Systems Conference
Breaking News
Newest First | Oldest First | Threaded View
User Rank
Re: Source impedance
MeasurementBlues   9/18/2013 11:55:05 PM
Doug Smith has several articles about how to make probes for all kinds of measurements. Here's one: DC to 1GHZ Oscilloscope Probe Plans

User Rank
Re: Source impedance
Steve.Picotest   9/17/2013 1:15:02 AM
1 saves
Thanks for sharing your comments.  You are correct and made some good points.  While I have made homebrew divider probes, I can't usually get good pulse performance above 1GHz.  I do use the Lecroy P65 and P66 transmission line probes.  These are much better matched than I could do myself, so I can achieve 7.5GHz and 47pS rise time with 0.75pF loading.  If you can tolerate the low impedance, and in most power applications you can, these are a great way to go.  I also like that they aren't keyed, so they work with any 50 Ohm equipment. 

Tektronix offers a great 1GHz passive 3.9pF probe and their TPP0850 800V/800MHz passive probe, with 1.4pF.  I measured the rise time of the TPP0850 at 970pS. 

I also have the Lecroy ZS2500 and ZS4000 active probes, which are excellent when you need the speed and these are very low loading at <1pF. 

I published an article recently in Power Electronics on measuring ripple that covers more on this subject of probing and cable matching.  There is also a chapter dedicated to it in my upcoming measurement book, which should be available in late 2014 with the tentative title Power Integrity: Measuring, Optimizing and Troubleshooting Power-Related Parameters in Electronics Systems



User Rank
Source impedance
jnissen   9/16/2013 11:23:28 PM
1 saves
You gave some fair advice but failed to mention why certain probe types work best in some situations. Source impedance often dictates what type of probe you can and should use. I often find myself creating my own resistor divider probes with simple coax and a couple SMT resistors. Very low capacitance and minimal loading on high impedance outputs. Active probes are great but sometimes you don't need them or want them. Been fooled lots of times relying on an active probe. Particularly nasty if you think you can use them for power supply ripple and droop analysis.

Top Comments of the Week
Like Us on Facebook

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Max Maxfield

ESC Minneapolis 2015 Sneak Peek! Baking Pis in Africa
Max Maxfield
Post a comment
One of the great things about my job is that so many interesting people get to meet me I get to meet so many interesting people (LOL). For example, I just received an email from Kurtis ...

Bernard Cole

A Book For All Reasons
Bernard Cole
1 Comment
Robert Oshana's recent book "Software Engineering for Embedded Systems (Newnes/Elsevier)," written and edited with Mark Kraeling, is a 'book for all reasons.' At almost 1,200 pages, it ...

Martin Rowe

Leonard Nimoy, We'll Miss you
Martin Rowe
Like many of you, I was saddened to hear the news of Leonard Nimoy's death. His Star Trek character Mr. Spock was an inspiration to many of us who entered technical fields.

Rich Quinnell

Making the Grade in Industrial Design
Rich Quinnell
As every developer knows, there are the paper specifications for a product design, and then there are the real requirements. The paper specs are dry, bland, and rigidly numeric, making ...

Special Video Section
After a four-year absence, Infineon returns to Mobile World ...
A laptop’s 65-watt adapter can be made 6 times smaller and ...
An industry network should have device and data security at ...
The LTC2975 is a four-channel PMBus Power System Manager ...
In this video, a new high speed CMOS output comparator ...
The LT8640 is a 42V, 5A synchronous step-down regulator ...
The LTC2000 high-speed DAC has low noise and excellent ...
How do you protect the load and ensure output continues to ...
General-purpose DACs have applications in instrumentation, ...
Linear Technology demonstrates its latest measurement ...
Demos from Maxim Integrated at Electronica 2014 show ...
Bosch CEO Stefan Finkbeiner shows off latest combo and ...
STMicroelectronics demoed this simple gesture control ...
Keysight shows you what signals lurk in real-time at 510MHz ...
TE Connectivity's clear-plastic, full-size model car shows ...
Why culture makes Linear Tech a winner.
Recently formed Architects of Modern Power consortium ...
Specially modified Corvette C7 Stingray responds to ex Indy ...
Avago’s ACPL-K30T is the first solid-state driver qualified ...
NXP launches its line of multi-gate, multifunction, ...
EE Times Senior Technical Editor Martin Rowe will interview EMC engineer Kenneth Wyatt.
Flash Poll