Oscilloscope probes - Page 1
Forum section: electronics / beginners

author: M84AB1
author_rank: Contributor
timestamp: December 13, 2011, 11:06:52 am
content: Hi gang,I have recently purchased a second hand (obviously hehe) Tektronix TAS 465 oscilloscope for AU$350 delivered. It did not come with any probes and it does have that 5V ring around the BNC connectors for those special probes with a metal pin at the end.As I am in the market for probes and looking for something that wont be the cost of my oscilloscope, I have come across these probes. Could anyone tell either from experience or just through industry knowledge which of the following probes are better and why and would be more suited for my scope. I was not able to find any decent second hand tektronix probes that would not cost about half of the cost of my scope.Also if anyone is selling some decent 150Mhz+ probes, send me a PM.Hantek PP-200, 200Mhz probehttp://www.ebay.com.au/itm/PP-200-200-MHz-Oscilloscope-Probe-X1-X10-Passive-/140646961746?pt=LH_DefaultDomain_0&hash=item20bf365252Uni-T, UT-P05 200Mhz probehttp://www.ebay.com.au/itm/Tow-Oscilloscope-Probe-Chip-Testing-Tool-200MHz-Kit-NEW-/280696559504?pt=LH_DefaultDomain_0&hash=item415ad19790Texas TEXAS 100/II, 300Mhz probehttp://www.ebay.com.au/itm/Probe-Oscilloscope-CRO-300MHZ-Passive-HP-/260895915023?pt=LH_DefaultDomain_0&hash=item3cbe9bbc0fTexas TX6150, 500Mhz probehttp://www.ebay.com.au/itm/500MHZ-Oscilloscope-Probe-Hp-Tektronix-/220906097562?pt=LH_DefaultDomain_0&hash=item336f078b9a

author: vk6zgo
author_rank: Super Contributor
timestamp: December 13, 2011, 02:59:30 pm
content: They all seem to have reasonable specs---obviously they aren't Tektronix,so they don't have the metal pin,& you will have to work out the x10 scale division in your head when in that mode.Don'ttry testing the 600volt rating in x10 position by hanging them across the AC mains,like some people have!Ideally,you would be best to get a x1 probeANDa x10 one,as the switch is a weak point in most switchable probes.All the gurus say,"Don't use a x1 probe",& I agree in most cases,but sometimes with very low level signals,they disappear into the noise with a x10 probe.Many workshops chuck those probes that have broken bits into a box somewhere,with the intention of making one or several good ones out of them,but they usually never get around to it,& the box is disposed of.If you are lucky,you may find one of these boxes with other junk at a Hamfest or similar occasion.HP, Philips,Siemens,or BWD probes may turn up on EBay from time to time,too.VK6ZGO

author: Unknown
author_rank: Unknown
timestamp: December 14, 2011, 12:37:42 am
content: I don't like 1x/10x switchable probes either, performance is usually worse than without for the higher bandwidth ones (even the Tek ones were problematic). Switches sometimes suck on cheap probes, I have a cheap no-name that can be switched between 1x, 10x and capacitively coupled (labeled GND). It likes to switch from 10x to 'GND' at random, until you apply some extra force to the switch to fix it.Quote from: vk6zgo on December 13, 2011, 02:59:30 pm1x probes are occasionally useful for low level signal, like ripple measurements. I would state it as "don't use a 1x probe if you care about bandwidth or can't tolerate the loading". Even if a 1x probe has 10MHz bandwidth, the loading at 1 MHz is already down to 1.6 kohm.I'm not sure if I'd pay extra for 300-500 MHz probes. If you need that kind of bandwidth, get a real Agilent/HP/Lecroy/Tek probe, 500 MHz is the top end for high-Z passive probes. For the TAS-465, a 100-200 MHz probe should suffice.

author: w2aew
author_rank: Super Contributor
timestamp: December 14, 2011, 02:22:31 am
content: I would agree with the advice given by others. Don't buy a wider BW probe than you need. A 500MHz probe will not extend the BW of the scope, and may not have the compensation range to properly compensate for the input capacitance of your scope. The TAS-465 is a 100MHz scope, so don't overshoot it much. In my opinion, I'd rather pick up a used Tek probe in good condition than a new inexpensive 10x probe. Avoid the switchable 1x/10x probes.

author: M84AB1
author_rank: Contributor
timestamp: December 14, 2011, 03:13:59 am
content: Thanks for the advise guys, sincerely appreciate it.Quote from: w2aew on December 14, 2011, 02:22:31 amYes I am am aware of that. The reason why I listed that 500Mhz probe is it is a readout probe with the special pin.The general question here is, Why are equivalent bandwidth probes from brand names like Tektronix, Agilent, HP alot more expensive? How do I know that the Hantek PP-200 for example is a truly 200Mhz probe. Will a cheap 200Mhz probe perform close to a more expensive 200Mhz probe when the highest frequency we are talking about here is 100Mhz?Quote from: w2aew on December 14, 2011, 02:22:31 amUnfortunately I am not able to find any inexpensive Tek probes that are also in good condition. There are a few listed for $40 delivered but their condition is horrific. I often wonder what people do with these things... clean their floor tiles with them?

author: vk6zgo
author_rank: Super Contributor
timestamp: December 14, 2011, 03:33:35 am
content: Quote from: alm on December 14, 2011, 12:37:42 amI definitely agree that x10 probes are best for most work,but the x1 probes can be handyIn many cases,loading & bandwidth limitations are less important than having a big, fat ,sassy RF source breathing down your neck which bypasses the probe & accesses the 'scope directly,increasing the noise floor.If the wanted signal is now attenuated by 10x,it disappears into this noise.Another use for x1 probes is in looking at dc levels in fairly low Z circuits,where the lower ranges on the instrument become useable.Another type of probe which is not widely used is a x100.I found this useful in some Sony Picture monitors for setting up HF compensation,where Sony suggested an active probe.My request for such a probe was not seriously considered,so I went for the x100 instead.It did a good job,although the necessity of using very low volt/div on the 'scope introduced the noise problem referred to above,though here,the RF came from the horizontal output stage of the monitor.VK6ZGO

author: ToBeFrank
author_rank: Regular Contributor
timestamp: December 14, 2011, 04:01:20 am
content: http://www.ebay.com/itm/HP-Agilent-N2862B-150MHz-Passive-Oscilloscope-Probe-NEW-/250891092001?pt=LH_DefaultDomain_0&hash=item3a6a464021#ht_542wt_1160Disclosure: That's my auction. But we might be able to make a deal if they work for your scope. And you know you're getting quality probes.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 14, 2011, 04:11:29 am
content: Everyday use of probes in Electronics workshops is not gentle,as Oscilloscopes are often the instrument of first choice,no matter what is being fixed,due to their extreme versatility.Also,the equipment being repaired may not be sparkling clean,so "gunk" from these ends up,particularly, on the probe leads.About the best cleaning a probe is likely to get,is a quick wipe over with a tissue with a bit of solvent on it.They usually lose their earth clips first,& then the probe clip body .Sometimes people using the probe tip bare without the clip body manage to break the tip off,so that an otherwise good probe is u/s.My probes are:- an "el-cheapo" bought new with a cheap CRO,several "Frankenstein" Tektronix probes rebuilt from "dead" ones chucked in the bin by an overzealous colleague,& an old "545" vintage x1 given to me by a colleague.Some of the probes on eBay may have a similar history to my "Frankensteins".VK6ZGO

author: Unknown
author_rank: Unknown
timestamp: December 14, 2011, 01:03:59 pm
content: Quote from: vk6zgo on December 14, 2011, 03:33:35 amAbsolutely, these fit within the "don't care about loading or bandwidth' criteria. A bandwidth limited signal above the noise floor is better than just noise. Another advantage is the accuracy. 10x probes usually have about 1% tolerance in attenuation. For example in differential measurements, this reduces the CMRR. 1x probes have no such problem.Quote from: vk6zgo on December 14, 2011, 03:33:35 amThat's a cheap way to get low loading if you can tolerate the attenuation.Quote from: vk6zgo on December 14, 2011, 04:11:29 amThat's a good point, pay attention to the accessories, especially with used probes. Critical accessories in my opinion are the ground lead and grabber hook. Also useful are the low inductance ground options (eg. the springy thing you slide around the ground sleeve) and a probe tip to BNC adapter. Something to grab onto DIP and SOIC would also be nice, but none of the cheap probe offer this, as far as I know.