Advice needed: Recommendations for an O-Scope

[Randybee1]

Hey guys, It's been many moons since I posted on here. I've finally put my Cat/Perkins 402d together, mated to a 7.5kW ST head. I'm looking to buy an O-scope but know absolutely nothing about them. Any advice would be appreciated. Money isn't an issue per say but I'm thinking I'd be willing to spend  few hundred $$ Thanks!

[AdeV]

There's a couple of major options for you... First, do you want a dedicated 'scope? If not -there's loads of very cheap USB "'scopes" which will capture a waveform & display it on your laptop/computer. As I understand it, they need a beefy machine to keep the sample rate up; and the risk of course is if you throw high voltages at it, you might fry your computer (although I'm sure they have decent isolation). I haven't used one of these things myself, must try one one day....

If you go the dedicated 'scope route, I'd strongly suggest buying second hand. It's one of those tools you won't use much, but when you do you want a good one... and a few hundred bucks won't buy much in the "new" world. There's loads of good machines out there second hand, though. My shopping list would look like this:
- Dual trace
- Digital storage
- Digital interface would be nice
- Something by HP,or Gould.

Alternatively, go proper old-skool and buy something absolutely ancient, but in keeping with the age of the typical Lister

I have both a "traditional" 'scope (dual trace, but 100% analog, round screen), and a somewhat more modern Gould with dual-trace, trigger-hold, and a few other nice-to-haves which make it more useful than the old machine, especially for trying to debug digital stuff. It's something I don't use especially often, but it has a permanent place on my bench because sometimes it's the only tool that will do the job!

If you find a nice HP 'scope, with a GPIO port on it, then you can hook it into one of the older HP computers (non-PC) & do all kinds of magic... the first job I ever had, fresh out of University without even a qualification to my name (I failed my course ) was taking the graph output from an HP scope & drawing it on the screen with the highest peak highlighted & all kinds of other stuff. All written in HP BASIC. I did enjoy that job...

Anyway, hope that helps narrow it down a little

[AdeV]

e.g. something like this: http://www.ebay.com/itm/391822776345

That is a disgustingly good bargain, and makes me jolly annoyed that I don't live in the USA right now!

Note that that does only have a GPIO output, which would be quite a challenge to interface to anything that isn't an old HP.... but who knows, maybe you like that kind of challenge?

[mike90045]

The saving grace is that 60Hz is pretty darn slow, and any scope & probes will work.   I think the cheapest/slowest scopes would be in the 1Mhz bandwidth range, so absoltly nothing fancy. 

But beware, the scope probes have a grounded shield, and it's common for stray voltage on the AC neutral, to fry the probe wire or the scope.  Often a small isolation transformer is used to prevent that.

[Randybee1]

Thanks for the advice guys. I am somewhat confused as I know nothing about O-Scopes. All I really want to do is look at my sine wave from my 3 ST Gen heads and maybe my inverter.
Usually when I buy a piece of equipment I buy the biggest most powerful there is but in this case I'm not too sure. So, here is what I'm thinking of:

https://www.amazon.com/gp/product/B071F1H3PG/ref=ox_sc_act_title_1?smid=AHHRXUADSMZS7&psc=1
Seems simple and straight forward for what I want.

OR....  https://www.amazon.com/gp/product/B00RJPXB6Y/ref=ox_sc_act_title_2?smid=A15QN6QABYC6HS&psc=1

What do you think? If I buy the little guy am I going to regret not getting the bigger one?

[vdubnut62]

One of the guys either here or over on the "other" forum used one of these on his ST head with great results. The price is right too.
Ron.

http://www.ebay.com/itm/Fully-Assembled-DSO138-2-4-TFT-Digital-Oscilloscope-1Msps-Probe-Adapter-Case/252531988039?ssPageName=STRK%3AMEBIDX%3AIT&var=551483907708&_trksid=p2060353.m1438.l2649

[BruceM]

I'd not bother with something under 1MHz bandwidth, or at least 10 mega samples per second.  I have used a simple portable Velaman scope for years and still find it very useful when I just quick look see at a signal for trouble shooting.   I almost never, ever use my Leader 60MHz dual trace analog oscilloscope.   I also have a $99 OWON 25MHz usb scope- which is a good product with built in usb isolation to protect your computer.  Unless you are using a laptop on battery only, and only looking at low voltages, don't use a USB scope without a USB isolator.  Only USB 2.0 is needed for most of the USB scopes, and a fast computer is not needed, either.  I use an older I5 based Dell Inspiron running W7 .  The cheap USB 2.0 isolators from China work fine.

My favorite for development work is my 25 MHz Picoscope with logic analyzer.  It's capabilities are amazing.  It does THC calculation (useful for checking your generator or inverter), spectrum analysis, and data captures that have spoiled me for anything else.  I typically set it up, turn on the offending equipment and then turn off the data capture and the equipment.  I can then scroll through and expand on the captured data at my leisure.  Triggering for data capture includes logic analyzer digital inputs.  I also like it as I can get great images for my notes, which are essential due to my bad memory problems.

On the low end, just try to stay at or above true 1MHz analog bandwidth (at least 10 mega samples per second ) so you can see spikes and such.  standard scope probes with BNC connectors are a big plus, and make sure that with a 10x probe setting you can see a 240VAC signal (+-350V peak) unless you are OK with getting a 20x probe.  I think a battery powered scope is much handier for any field troubleshooting and the price is such these days that it's not a bad place to start.  Pay attention to reviews for ease of use if you are a complete novice. 

This outfit carries some amazing benchtop scopes.  Most people don't find USB scopes worth the bother now that these stand alone digital scopes are so powerful and cheap.  My health problems preclude me from using them or I likely would as well.

https://www.circuitspecialists.com/digital-storage-oscilloscopes