Value for money in good passive probes - Page 1
Forum section: electronics / testgear

author: andrewwong2000
author_rank: Contributor
timestamp: August 10, 2014, 02:57:21 pm
content: I spent tonight looking at probes...i. 500Mhz bandwidthii. Slim profile (2.5mm tips)iii. Good back of accessories suited to probing QFP, SMD.I landed at :i. Brand Name stuff : LeCroy PP008, Agilent N2873, Tek equiv. around US$350-400 each (ouch)ii. Looks like OEM versions of the Agilent N2873.. PMK PML711 (exxy), Picoscope TA133 (US$210),iii. Give up on a slim probe and in 5mm there's heaps of them Pomona (on sale $80), Texas, etc.I'm leaning to sticking with my bog stock N2890 probes and hooking up some E-Z Hook X2015 micro grabbers.The Picoscope TA133 looks the most value for money of the lot - apart from the lack of RO pin (not a deal breaker).Any others I should consider ?

author: nctnico
author_rank: Super Contributor
timestamp: August 10, 2014, 03:17:31 pm
content: Forget about measuring any signal over 100MHz with a high impedance probe. The capacitance at the tip is usually around 10pf which loads a real world circuit way too much. Better buy some cheap 150MHz probes (Testec has nice ones) and get 50 Ohm passive divider probes for HF stuff.

author: David Hess
author_rank: Super Contributor
timestamp: August 10, 2014, 03:59:19 pm
content: I agree with nctnico.High frequency passive probes are specified using a 25 ohm source and coaxial connection which is unrealistic for general purpose use. With a spring ground connection they can be used with low impedance signals but they are never going to perform as well as the alternatives. Micro-hooks will completely compromise high frequency performance just like having a long ground lead.I have gotten good results with the 250 MHz Texas probes which are available cheap but when it matters, I use them with a coaxial connection.Low impedance passive probes are easy to make and even active probes are not too difficult for when you absolutely have to high low input capacitance and high input resistance. The same caveats about short or coaxial connections still apply.Your list for probe sources pretty much duplicates mine. If you are including PMK, I would add Testec:http://www.testec.de/passive_tastkoepfe.0.html?&L=1I am sure the Picoscope probe you mention is OEMed by PMK.I did not know E-Z-Hook made oscilloscope probes. I will have to add them to my list of alternatives.

author: Carrington
author_rank: Super Contributor
timestamp: August 10, 2014, 05:52:30 pm
content: I have on sale two N2890a:https://www.eevblog.com/forum/buysellwanted/fs-agilent-hp-n2890a-probe-set/msg353191/#msg353191

author: edavid
author_rank: Super Contributor
timestamp: August 10, 2014, 05:53:50 pm
content: How about used HP 10430A/10431A/10441A?

author: larry42
author_rank: Regular Contributor
timestamp: August 10, 2014, 07:16:53 pm
content: Quote from: edavid on August 10, 2014, 05:53:50 pmI would nor consider used probes. Probes have a finite mechanical life. ..Just bought PMK 311 (350MHz, 2.5mm) they appear good quality (better than thevnew Agilent 150MHz proves)Sent from my One S using Tapatalk

author: nctnico
author_rank: Super Contributor
timestamp: August 10, 2014, 08:49:09 pm
content: I agree. Used probes are like used shoes and underwear. You don't want those!However for high-end probes like active FET or passive divider an exception can be made. These are usually used much less than general purpose probes and their cost is much higher so it is likely that people handle these more careful.

author: edavid
author_rank: Super Contributor
timestamp: August 10, 2014, 08:58:38 pm
content: I don't know, I've had about a 90% yield on used probes. Very cost effective, for me.

author: HighVoltage
author_rank: Super Contributor
timestamp: August 10, 2014, 10:44:17 pm
content: Quote from: andrewwong2000 on August 10, 2014, 02:57:21 pmI have a set of both of these probes and I bought them all on ebay around the world.With a little time you can get them for a fraction of the new price.Interesting, both of them say: "Made in Germany"They do look very similar but not the sameI wonder who makes them in Germany for both of these company's

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2014, 12:56:14 am
content: If you have a good pulse generator, then it is easy to test probes to verify that they are functioning correctly so there need not be any uncertainty with used ones.

author: AwArD_RzD
author_rank: Regular Contributor
timestamp: August 11, 2014, 12:58:34 am
content: For me Ebay is the best place for that but you need to be careful and not in a hurry.i scored a new N2890a probe at 14.95$ + s/h this week and i got a new PP005 lecroy probe at 36$ in may, all new in the original bag with accessories, use the following search item option in ebay and wait, you can get some very good deal.

author: andrewwong2000
author_rank: Contributor
timestamp: August 11, 2014, 02:15:40 am
content: N2890 is a 500Mhz probe .. but it is a 5mm body item. It's the "cheap" Agilent 500Mhz probe and isn't really great for SMD probing. $14.95 is still a good price but it doesn't come with accessories. If Agilent bundled 4 x N2873s with my MSOX3054, I'd wake up next to Robbie Margot tomorrow.The cheap N2873s on eBay that are 2nd hand are salvaged and don't usually come with the 2.5mm accessories. You can buy a kit from Pico for about $65 that gives you all the bits that fit. Worth waiting for.

author: HighVoltage
author_rank: Super Contributor
timestamp: August 11, 2014, 09:20:52 am
content: Even my MSOX3104A came with the low cost N2890 / 500Mhz probesIt is a surprise that Agilent does not bundled the 4 time N2873 probes with the high speed instruments.The quality between the N2890 and the N2873 is huge, not only the tip but also the BNC connector and the cable itself is of lower quality.

author: Bryan
author_rank: Frequent Contributor
timestamp: August 11, 2014, 09:53:36 am
content: Quote from: David Hess on August 11, 2014, 12:56:14 amWould be interested on the test procedure. Are you able to elaborate. Cheers.

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2014, 01:21:14 pm
content: The test comes down to applying the output from a reference flat top pulse generator to the probe via a feedthrough termination and coaxial adapter. The idea is to check and if appropriate adjust the transient response for a minimum of aberration. The rise time of the pulse edge will also reveal the system bandwidth.Bad probes will either be slow or have unacceptable transient response.

author: nctnico
author_rank: Super Contributor
timestamp: August 11, 2014, 01:26:41 pm
content: The biggest problem with probes are poor ground connections and intermittant contacts / broken cable.

author: larry42
author_rank: Regular Contributor
timestamp: August 11, 2014, 02:53:20 pm
content: Quote from: David Hess on August 11, 2014, 01:21:14 pmIMO the worst problem is intermittent connections (after 5years I've seen 4/4 HP 10441B 2.5mm probes fail intermittent)Sent from my One S using Tapatalk

author: marshallh
author_rank: Unknown
timestamp: August 11, 2014, 10:21:50 pm
content: Look out for lecroy PP005,PP006 probes. Can be gotten for $80But I agree you have no business probing stuff over 100mhz this way. It just loads it down so much.