Time for a new scope

[MagicSmoker]

Well, folks, I've gotten by with my THS720 for many years now. It's been a fantastic scope - definitely one of the best-engineered products I have ever used - but it is definitely showing its age because more and more I find myself wishing for faster/better transient capture and math functions, maybe even do a little FFT now and again. I basically design high power SMPS, motor drives and such; only occasionally do I need to track down glitches on digital lines and that is usually in association with the high power stuff going on nearby.

So I'm in the market for a new portable scope. I do tend to lean towards Tek just because, but I'm open to other suggestions - just none of that Chinese rip-off crap. Four isolated channels (I use a diff. probe for the critical stuff, but like to be able to poke regular probes without blowing up the input stage, too). A 100MHz is plenty as ringing and the clocks I work with are generally below 30-40Mhz. I could definitely use more sample depth and speed - the 500MS/s rate claimed by the THS720 ain't cutting it at all (I have to be very patient and get lucky to catch a lot of glitches these days). Maybe a little larger screen than the THS720's 4.87", but the size of the scope itself is perfect. Oh, budget range is, say, $2k to $5k.

The new Fluke 190 series ScopeMeters *look* nice, but unless they have radically improved their user interface I wouldn't touch one with the proverbial 10' pole. The Agilent handheld scopes would be a step backward for me, but even their 1000 series "portables" look like a quantum leap in features, anyway... too bad they are stretching my definitely of portable.

In short, I would love to have a more modern version of my beloved THS720, but it seems Tek killed that line off some time ago.

I'm mainly looking for opinions from my esteemed peers on this.

 

[Skogsgurra]

LeCroy has came down in price, I think. I have used a Wavesurfer 424 for quite a while. No isolated inputs, use isolation amplifiers when needed. 2 GSa/s and 200 MHz BW have served me well. Has FFT and a couple of very useful Analog Persistance functions. Long memory, good screen capture but waveform store not so good.

I travel a lot and have been using small USB devices. PicoScope has good BW, but very sensitive inputs. Blown a few of them and not very happy with the support when something goes wrong. Never blew any input on any other scope.

TiePie is quite good, but somewhat slow - mine are 50 MSa/s. Four channels at some USD 2000, no extra power supply and small/light. Can be had with floating inputs. Perfect for travelling. But user interface designed by someone that never used an ordinary scope. Good math functions. DC offset worse.

I have also tried other small USB units. Will visit trade show next week and try out some new units.

Be back after that.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[benta]

In my experience, one quality test is to check how good the video trigger is. This can say quite a lot about how much design effort was put in the scope. You need access to a video source, though

Benta.

 

[MacGyverS2000]

I'm not a fan of the later models of scopes that run an OS (like WinXP)... I've seen a surprisingly large number of those scopes rendered unusable until repaired (by the factory at high price) because the OS became corrupted. I understand the concept of putting an OS on there for faster development and increased functionality, but not if it means a significant increase in "bricked" incidences. At my last job, we lost one $50k scope because the battery-backed RAM went tits up (and you couldn't get past the BIOS screen), and a second $40-50k scope because it thought the keyboard had a stuck key. Management was too busy to send them back for repair for months, so we were down two scopes.

Just something else to consider...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[MagicSmoker]

Hey Gunnar... the LeCroy's seems to be outside of my budget, unless I go with the Wavejet. The Wavesurfer series looks extremely nice, though, I gotta say. I couldn't tell from a quick overview if the inputs are isolated or not, but I have to have isolated inputs. I'm too absent-minded to get by without that.

Don't even get me started on "embedded" products running Windows, Macgyver... You didn't come right out and say it, but I'm guessing you are referring to Agilent here?

Either way, I'm not buying a $40k scope for myself anytime soon.

 

[ScottyUK]

Feature-wise the Agilent scopes were a fair way ahead of the equivalent Tek TDS3000 series in memory depth and triggering ability when I looked at them a couple of years ago. I still think the Tek scopes were more intuitive to use but less technically capable for the same money.

Isolated inputs takes you to the TPS2000 series but it is getting long in the tooth and Tek don't seem to have any intention of updating it to increase the memory depth and signal handling capability, and add ethernet and USB support. A shame because it is a good scope, just expensive for an increasingly dated feature set.

I still love my Tek 2465B - for some purposes a decent analogue scope is still able to give most DSO's a good run for their money. Looking at partial discharge pulses is one such application - you need a heck of a fast DSO to get enough single shot bandwidth.


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If we learn from our mistakes I'm getting a great education!

 

[MagicSmoker]

Yeah, I am distinctly unimpressed with the TPS series, now that I have seen the offerings from LeCroy and Agilent. However, it is difficult for me to trust anything besides a Tek scope... an attitude that Tek might be counting on. Dunno. Wouldn't be the first time a once might tech company fell by the wayside because it rested for too long on its laurels.

 

[Comcokid]

I've used the Tek TDS3000 series for about 10 years now, and have found them among the best general purpose digital scopes Tek has ever made. The problem with them is that the series is now 10 year old - and for an electronic product model line, that is old. They're now into the third generation with the "C" versions and a thumb-drive interface. I've always found them very intutive to use. But the FFT resolution in these scopes is now not the greatest and the trigger filtering which was great 10 years ago now needs more features.

I do some SMPS work and I use a generic HV differential probe which I power from the 15V output jack on the back of a TDS3034B and a little regulator module I made to provide the 6 volts for the probe. Otherwise, you can use the nice Tek P5205 or P5210 which power from the Tek probe interface, but they're almost as expensive as the scope.

Don't bother with the TDS2000 series. My ME degree boss bought some to save department money over the objections of the EEs, and frankly they're only suitable for a bench at a high school for basic circuits. By trying to save money, he threw it away.

I've also used a newer Tek DPO4000 series with the power analysis package software option, and it seemed really good, especially the THD analysis for use with inverter circuits. But I found the documentation of the power package non-existant. When you're doing SMPS work, you want to know how the waveform is being analyzed so you know how it's really analyzing and not-analyzing in the waveform.

 

[itsmoked]

Well this is a sad state of affairs... My THS720 is sitting here ON next to me and my Tek 2465 sits gathering dust. I love the THS for the isolated channels since half the stuff I do includes line voltages driven by isolation schemes. It's a godsend. The battery choked at least 6 years ago.

If it died I'd want to replace it with the same small size, isolation, and features.

Isolated scopes aren't hard to build but they all have the bad habit of The Wandering Zero. Since they're floating there's no ground reference so I have to disconnect the probe and re-zero every time I change the scale button. That's the main annoyance.

I can't offer any solution Smoker but I'm following with you.

I think LeCroy is working very hard to bring together form, function, features, and value. I would look very closely at their line if I was faced with needing a replacement. Perhaps just use isolated probes - always - so there's no thinking about them, would be the path to follow. That opens the choice of scopes up to them all..

Keith Cress
kcress -

http://www.flaminsystems.com

 

[MagicSmoker]

Alright, so apparently I'm not alone here in thinking that Tek was crazy to discontinue the THS720! WTF were they thinking? I can live with the lunch box form factor of the TPS2xxx series but the sample depth of 2500 points is exactly what I have now! C'mon, Tek! My THS720A is 15 years old!

So the TPS20xx is totally eliminated from consideration - just not enough of an improvement.

I don't need a logic analyzer so the MSO series is out.

Can't tell much difference between the models in the DPO2/3/4xxx series except in software functions, and sample rate/length. None of them have isolated inputs, apparently, and can't run on batteries, so that might be too much compromise for me.

Actually, I could live without the battery power, but I'm pretty sure I would get very annoyed destroying scope probes on a routine basis from the non-isolated inputs, and having to always use differential probes is, a) expensive and, b) really expensive if you need more than 20-25MHz of bandwidth.

BTW - itsmoked, I am on my 3rd battery pack for my THS720, and I had the last two made by Batteries Plus for $26. I've been getting about 3 years from each one.

 

[itsmoked]

MagicSmoker; Thanks for that tip.

Keith Cress
kcress -

http://www.flaminsystems.com