Probes ..name brand vs Chinese ebay probes  - Page 1
Forum section: electronics / beginners

author: nrgeek
author_rank: Contributor
timestamp: January 23, 2012, 08:28:14 pm
content: Hey all .. I bought a tektronix 465M analog scope off of eBay for 85 including shipping , didn't come with probes.. so I'm needing to buy 2 probes to go with it .. the prices on these are from one end of the scale to the other.Chinese probes run around 8 to 40 dollars .. and the name brands tek etc 50 to 300 .. I know this is prob a stupid f'n question .. cause generally the china stuff is crap .. but my budget is tight .. at the same time don't want to buy crap that I need to replace with name brand probes.. and end up spending more than if Id just bought the name brands to start off with.Have any of you bought these probes ? and what is the quality compared to name brands ?here is linkhttp://www.ebay.com/itm/2X-Probe-CRO-100-MHZ-100MHZ-1X-10X-HP-Tektronix-/320822566107?pt=LH_DefaultDomain_0&hash=item4ab283dcdb#ht_2541wt_754Thanx a bunch in advanceSeanGeek by Birth, Linux user by Choice

author: Lightages
author_rank: Unknown
timestamp: January 23, 2012, 09:52:19 pm
content: They look OK, just like anything does in pictures. You will know they are OK when they don't break or get noisy after 5 years. There is definitely no sense in spending more than the scope for probes. My advice is to buy probes with a higher bandwidth than the scope if you can afford it.Consider one of this probe as an additional purchase:http://www.dealextreme.com/p/250mhz-oscilloscope-probe-max-1200v-35610It seems to work as advertised although I cannot attest to its performance.

author: Unknown
author_rank: Unknown
timestamp: January 23, 2012, 10:17:36 pm
content: I don't see the point of buying a DX 100x probe. Perfomance will suck for low level signals, and I wouldn't trust it with anywhere near 1200 V.Brand name (i.e. HP/Agilent, Lecroy, Tektronix, probably recent PMK designs) usually have a better signal integrity (eg. dielectric absorption and voltage coefficient in the input cap), less loading, better durability, more flexible cable, better access to tiny circuits (hello cheap probe makers, please start cloning thirty year old brand-name probes instead of forty year old ones, most of us don't use tons of 1 W resistors and tubes anymore).That said, the cheaper brands are likely to work just fine for hobbyist applications with low bandwidth (< 300 MHz or so) scopes. Just don't expect them to last for years of serious use, most of them won't.You can sometimes find cheap Tek probes on eBay, though you have to make sure you get the essential accessories (at least ground lead and grabber hook). Pay attention to attenuation (10x is by far the most versatile), compensation range (should include the input capacitance of your scope) and bandwidth (preferably at least 100 MHz).Probes tend to be relatively more expensive than scopes (maybe 10% instead of 1% of the original price) mainly due to supply and demand. Probes are frequently thrown away by surplus companies to be sold for scrap, or tend to get lost or damaged much more often than the scope.

author: Lightages
author_rank: Unknown
timestamp: January 24, 2012, 12:01:58 am
content: I did mean to say that I don't trust the DX probes for 1200 volts either, thanks for pointing it out. The idea for the DX probe was to get a wider bandwidth than his scope has and not for 10x the price he paid for his scope. I do not know if the DX probe meets its bandwidth spec but it has the same chance as the other probes he listed of meeting their spec.My advice on the probes were based on his apparently very tight budget.

author: vtl
author_rank: Regular Contributor
timestamp: January 24, 2012, 02:13:34 am
content: The probes in the OP look fine for hobby use.Aren't the BNCs supposed to be insulated though? Definetly don't use it on a floating scope.

author: nrgeek
author_rank: Contributor
timestamp: January 24, 2012, 02:33:38 am
content: Ok maybe this would be a good video blog for Dave .. like he doesn't already have a shit load of video request now.. Shit seems to be Dave's fav word and cracks me up lolThis is shit , that is shit .. Dave is so funny and informative at the same time.Ok Dave if your listening aka reading .. how about a review of the china probes vs the name brand probesand while your at it how about the china esr meters and power supplies vs brand names lol .. us broke folks need to save money any way we can lolstill looking for some one who has bought these lower cost probes recently to give their opinioninquiring minds wana know

author: vk6zgo
author_rank: Super Contributor
timestamp: January 24, 2012, 05:28:06 am
content: Quote from: alm on January 23, 2012, 10:17:36 pm100x probes are not really intended for looking at high voltages,but rather as a 'Cheap & dirty" alternative to an active probe for looking at high impedance circuits where the 10MOhms of a x10 would adversely affect the circuit operation.I was adjusting a Sony Picture monitor,where the book advised the use of an active probe for this reason."Nonsense!" said I,and tried a x10-----well,Sony were right!I asked the boss for an active probe,& after he finished rolling on the floor laughing,he suggested somewhat forcefully,that I find an alternative way to provide the required high Z input on the 'scope.A x100 probe from RS Components was the answer,although the signal was a lot fuzzier than with the x10,it was now possible to adjust it correctly.Tektronix probes don't always fail in the same manner,& I have assembled probes using various "broken" units assigned to the bin.I call them my Frankenstein probes!"Time is money" in most workshops,& sometimes even expensive probes which may need a minor repair are put to one side & forgotten in the rush to complete the customer's jobs,so if you are lucky enough to find a bundle of Electronic junk from a workshop for sale somewhere ,you may find some Tek or HP probes in amongst the other bits.VK6ZGO

author: Unknown
author_rank: Unknown
timestamp: January 24, 2012, 09:52:06 am
content: Quote from: vk6zgo on January 24, 2012, 05:28:06 amDon't tell that to the tube guys. Capacitive loading is indeed a valid issue, although I'm not sure how well the impedance of the DX probe would behave at higher frequencies. Someone on the TekScopes list compared the conductance at 20 MHz between some cheap (ProbeMaster?) probes and an old Tek probe, and the Tek probe was about an order of magnitude lower.Quote from: vk6zgo on January 24, 2012, 05:28:06 amSure, the 3 pF or so is much better than the ~10 pF of a good 10x probe. This does not make 100x probe a good first general-purpose probe, though. You touch upon an important point: the output impedance of your test point is critical. Probes are usually tested with a signal generator with a 25 ohm output impedance (50 ohms output terminated into 50 ohms). Their bandwidth -3 dB spec is with this (low) output impedance, and will be down to something like 160 ohm for a good 10x probe at 100 MHz. Performance with a high-impedance source will be dramatically worse (try to calculate the -3 dB point for a 1 kohm source impedance). This is where good probes, and also specialized probes like FET, 100x and Z0, come in. You won't see much difference on a signal generator, but loading in real circuits will be much lower.Tektronix' ABCs of scope probes (can be found on their website) and Oscilloscope probe circuits (can be found on various other websites), old, but quite detailed are good reads for more information.Quote from: nrgeek on January 24, 2012, 02:33:38 amI got some cheap no-name probes with a scope I bought (not exactly recently though). Two of them seemed to work fine for low-bandwidth work (never used them for anything critical). One had a dead switch that was hard to reach, would switch to GND coupling unnoticed and which would capacitively couple the signal on that setting. Suddenly your signal is much weaker and high-pass filtered.

author: saturation
author_rank: Super Contributor
timestamp: January 24, 2012, 12:44:39 pm
content: I tested similar ones a while back, and they are not bad. There is an archive post of a comparison of the performance of something similar and the Rigol 200 MHz probes.Be aware the characteristics of the probe will affect the quality of the input so always good to test its performance to its rated bandwidth, to see what kind of distortion it could introduce, don't rely on its published specs but see what the actual probe you bought does. The 100 MHz rating is the -3dB point, so amplitude is down ~30%; non sine waves will be distorted by the bandwidth limits; e.g. a 20 MHz square wave will have ~ 100 MHz edges and it will be rolled off on the scope, both by the probes and the scope, as expected.Quote from: nrgeek on January 23, 2012, 08:28:14 pm