Breaking News
Comments
Newest First | Oldest First | Threaded View
MeasurementBlues
User Rank
Author
Re: Source impedance
MeasurementBlues   9/18/2013 11:55:05 PM
NO RATINGS
Doug Smith has several articles about how to make probes for all kinds of measurements. Here's one: DC to 1GHZ Oscilloscope Probe Plans

Steve.Picotest
User Rank
Author
Re: Source impedance
Steve.Picotest   9/17/2013 1:15:02 AM
NO RATINGS
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

 

 

jnissen
User Rank
Author
Source impedance
jnissen   9/16/2013 11:23:28 PM
NO RATINGS
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.



Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
Radio
LATEST ARCHIVED BROADCAST

What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.

Brought to you by:

Like Us on Facebook
Special Video Section
Once the base layer of a design has been taped out, making ...
In this short video we show an LED light demo to ...
The LTC2380-24 is a versatile 24-bit SAR ADC that combines ...
In this short video we show an LED light demo to ...
02:46
Wireless Power enables applications where it is difficult ...
07:41
LEDs are being used in current luxury model automotive ...
With design sizes expected to increase by 5X through 2020, ...
01:48
Linear Technology’s LT8330 and LT8331, two Low Quiescent ...
The quality and reliability of Mill-Max's two-piece ...
LED lighting is an important feature in today’s and future ...
05:27
The LT8602 has two high voltage buck regulators with an ...
05:18
Silego Technology’s highly versatile Mixed-signal GreenPAK ...
The quality and reliability of Mill-Max's two-piece ...
01:34
Why the multicopter? It has every thing in it. 58 of ...
Security is important in all parts of the IoT chain, ...
Infineon explains their philosophy and why the multicopter ...
The LTC4282 Hot SwapTM controller allows a board to be ...
This video highlights the Zynq® UltraScale+™ MPSoC, and sho...
Homeowners may soon be able to store the energy generated ...
The LTC®6363 is a low power, low noise, fully differential ...