Tektronix Design FAIL - Page 1
Forum section: electronics / testgear

author: blueskull
author_rank: Unknown
timestamp: November 22, 2015, 04:10:39 am
content: So let's cut things short, WhyTF Tek VPI power has to be supplied from an external power supply? They built a 80W PSU in their DPO2000B scopes, so why can not they pack another 50W in it and free their product from an optional silly power supply for probes?----------------------------- Long Story -------------------------------A couple days ago I had a need to measure current waveforms, so I took a current clamp ($4500 model from Tek) from our lab's storage cabinet. After connecting it to a DPO2024B's Tek VPI interface, the scopes shows "insufficient power, external supply required" message.With a normal person's logic, when a probe requests for power, it should be a power jack in the probe, so I took minutes to examine the probe many times, in the mean time, I tried and examined 3 different models, no DC jacks at all.Desperate and helpless, I took a look at the scope itself, voilla, there is a bloody DC jack (hidden) in the side panel of the scope! WTF, are you kidding me? A scope can not supply its own probes, and needs external power, not feeding into its probes, but the scope itself? Epic design fail.I can understand if a probe needs more power than a scope can supply, just add a DC jack to the probe. They instead added the DC jack to the scope. So if they anticipated this situation in the early product planning phase, why not build the damn thing into the scope?Admitted I had not read its manual, but hey, leave a comment if you read manuals before using a scope that is not your main productivity one. I've used scopes from cheap Owon ones (a real one and an usb one, both 100M/1G), digilent analog discovery, rigol ds6102, to mid-range hpak msox3104a (my current productivity one) and many teaching lab crap ones that probably are older than me. Never had to read manuals except for the first one I've ever used (Owon SDS7102, I still keep it).It is not rocket science, and Tek has more than enough capability to add an extra 50W into the chassis, so why not? For low noise? No, their optional PSU is also SMPS. For making more money? No, the active current probe itself is $4500, why save $20 and outrage a customer?Oh, finally, it sells for about $3000, I would not expect a piece of non-competitive model to be that expensive. A Rigol DS2202A or HPAK MSOX2024A outperforms it by almost all aspects, and both are considerably cheaper, let along the famous and popular DS2072A can be hacked to a DS2202A.

author: Tom45
author_rank: Frequent Contributor
timestamp: November 22, 2015, 04:24:42 am
content: Not knowing the relative age of the scope and the probe, my guess would be that the scope predates the probe. Perhaps when the scope was being designed they wanted to future proof it to work with whatever probes might come along in the future, no matter what their power requirements might be.In this case the probe only needs 50 watts. Perhaps in the future another probe might need a few hundred watts. Their external power supply connection allows for flexibility to deal with whatever the probe gurus come up with in the future.That doesn't make it any less frustrating to the person that hasn't read the manual that closely. And no, I probably wouldn't have read that part either.

author: Cubdriver
author_rank: Unknown
timestamp: November 22, 2015, 05:49:30 am
content: Perhaps the idea was to supply the aux power internally through the scope so that if multiple probes were used they could simply be plugged in to the scope without requiring additional connections (other than the single one to the scope itself) having to be made. If the power jack was on the probe, if you have an application where you need to used two or more of the powered probes, you'd start to wind up with a rat's nest of cables, and when swapping probes in and out have to make additional connections for external power. If it's supplied through the scope, you plug the probe in and (assuming that the external power supply is connected) you're good to go.As others have suggested, maybe it's not built into the scope because other probes might require more power, and/or powered probes might be rarely used by most operators of the scope. If that's the case, then providing additional headroom in the internal power supply would be a waste for most users, and the bean counters may well have decided not to build it in if, say, only 1 in 10 users would know or care it was there. I'm not saying it's right, just offering a reason why it may be designed that way. Remember, this is not the Tek of old - these days the totalizers of legumes have a say in everything and a strong veto power.-Pat

author: German_EE
author_rank: Super Contributor
timestamp: November 22, 2015, 09:10:48 am
content: Fifty Watts is 10V @ 5A, that's a reasonably large power supply to fit inside your scope case plus there will be additional weight and heat issues. Also please do not forget that not all users have your particular needs so if I bought the same scope I would have to pay for an additional power supply that I do not need.

author: nctnico
author_rank: Super Contributor
timestamp: November 22, 2015, 09:26:39 am
content: Quote from: Tom45 on November 22, 2015, 04:24:42 amNo. The scope supports current probes and it has been known for decades that current probes need a lot of power. I got a TDS2000B + current probe for a customer (primarily because of the brand name for political reasons) and also frowned when I noticed the current probe needed an additional adapter. Very clumsy because it also means bringing along an extension cord with at least two outlets.Spending $2 more to make the power supply a little bit bigger in order to supply a couple of probes would have been a much better option but IMHO it is a tell-tale sign that the days of Tektronix have passed.

author: timb
author_rank: Super Contributor
timestamp: November 22, 2015, 10:37:30 am
content: As far as I know, all of the smaller TekVPI scopes won't power *any* probe at all (even at 1.5W) unless the external adapter is plugged in. The larger scopes (that are essentially just a PC with scope hardware tacked onto the bus) will power them.Keep in mind a larger PSU means a bigger, noisier fan and a much more complicated thermal design.Personally, I'd rather my scope be quieter and lighter 99% of the time I'm using it, and then plug in an extra power brick the additional 1% of the time I need one of these probes. Also, plugging a single external brick into the scope and having it split off to 4 probes is a lot better than plugging 4 bricks into 4 probes.Finally, SMPS have come a long way in even the last 10-15 years. Comparing a 15 year old scope to a new Keysight isn't really a fair fight, now is it? (Plus, the newish Tek MDO series scopes can power probes without an external brick.)Sent from my Tablet

author: timb
author_rank: Super Contributor
timestamp: November 22, 2015, 11:07:01 am
content: Quote from: blueskull on November 22, 2015, 10:43:24 amThe DPO/MSO2000 series is a repackaging of a TDS series scope originally released in 2002. They basically upgraded the ADC, added the digital phosphor stuff and a new case, then called it a day.Have you ever noticed how dog slow it is? That's because it's a woefully underpowered 15 year old scope built to a price!I'm just saying, of all things to complain about on the DPO2k, you pick having to hook up a power brick to use probes that cost more than the scope itself!Now, don't get me wrong, it's not a *bad* scope. It's rock solid, accurate, easy to use and well laid out. My daily driver is an MSO2024B, though there's no way I'd pay Tek's MSRP; I'd pay $999 for one though. (Full Disclosure: Mine was provided by Tek for free two years ago.)Sent from my Tablet

author: nctnico
author_rank: Super Contributor
timestamp: November 22, 2015, 11:08:15 am
content: Quote from: timb on November 22, 2015, 10:37:30 amOfcourse not. The PSU can be made more efficient and with a decent design 95% efficiency can be achieved for a few dollars extra. Either way it is not the PSU which needs cooling but the electronics powered by the PSU. In the end all the energy delivered by the PSU is converted into heat. However an external device dissipates outside the casing so a more beefier PSU doesn't mean the fan needs to be bigger!

author: poorchava
author_rank: Super Contributor
timestamp: November 22, 2015, 11:26:15 am
content: I often use MSO2024 at work. It's crap in the sense that it's slow and the UI is bad. When they decided to use a wide screen, they could've placed the context menus on the sides, not on the bottom. This way the menus wouldn't obcure half of the screen.HP/Agilent/Keysight are simply better.Sent from my HTC One M8s using Tapatalk.