Shopping for an Oscilloscope

I would go with one from the Rigol DH0800 series: https://www.rigolna.com/products/rigol-digital-oscilloscopes/dho800/

...and Dave Jones seems to agree: https://youtu.be/S8jrpCoZyx8?si=zwkt5gDHuKAWtgig

softwarejanitor wrote:

Unfortunately that series of Rigol is a bit out of my budget right now.  The 100MHz 2 channel is around $400 and the 4 channel or 200MHz models are even higher.

 

Based on good reviews I ended up going with the Hantek DSO2D15.  It is 150MHz and 2 channels but also includes a waveform generator.  It was around $230 with free shipping frm Amazon and they promi

It'll probably get the job done for you! Congrats on your new workbench tool. 

... this is meant for those who did not yet make a purchasing decision.

1. Channels: you need at least two to be able to measure time differences from a signal edge to another signal.

2. Bandwidth: for work on 1 MHz clocked Apple-1 and Apple II, 20 MHz is enough. I know this because my 150 MHz scope has a button for 20 MHz bandwidth limit, which I use often to get rid of the high frequency garbage polluting the signal. You can compensate for limited bandwidth in time difference measurements easily.

3. Sweep speeds: 100ns/div is a must for Apple-1 and Apple II work. 50ns/div and 20ns/div is even better. My scope can write up tp 2ns/div but then the trace gets quite dim and the work must be done in a darkened room.  Tektronix had the patented "microchannel" image amplifier plate in some of their analog scopes which gave excellent brightness of the trace even with very high sweep speeds, but old Tektronix scopes must be avoided (unless $1 or free).

4. Analog scope or digital ?  I never really needed a digital scope in 40 years of IC design, but as the companies I worked for slowly replaced the ageing analog scopes with digital ones, I had to use digital scopes, too. Which I hated because with them you can't see a lot of information buried in the signal. For instance, if you have a noisy signal then the brightness band of the signal seen on an analog scope can tell you a lot about the amplitude distribution in the signal. An analog scope will also allow you to see rare glitches or spurious events more readily than a digital scope, because the phosphor will capture and show even the rarest events and signal excursions. It may be necessary to work in a darkened room to see these. But a digital scope only will capture one snapshot of signal at a time, and depending on the refresh rate of the screen you may miss such rare glitches or events completely. There is a reason why Tektronix developed (and patented) the "digital phosphor" technology for their digital scopes. Because too many practitioners complained about the analog scope capabilities that were lost when going digital.

CAVEATS

If you buy any modern, new, Chinese made scope you need to regard this as a disposable item, as you won't be able to repair it (or get it repaired) at any reasonable cost. The rubber keys have been known to decompose within a few years and then it's done for. Same issue, BTW, with rubber keys on any instrument made by HP, Agilent, Tektronix etc. . . . the brand name cannot compensate for decomposing synthetic materials.

Avoid old Tektronix scopes which have hybrid modules for the plate amplifiers. These modules die often and are unobtainium. Even older Tektronix scopes which still have a few tubes in them (other than the CRT) known as "dog houses" or "boat anchors" can be repaired but their bulk and weight is a problem (unless you have a boat). All the transistors in them are socketed and still spells trouble when it was stored in a humid basement or attic. Once the contacts are corroded it's game over.

You can buy old analog scopes which once did cost a fortune for pennies on the dollar. Ebay is full of them, and as long as the vendor shows it can produce a waveform picture (and not just a flat beam) it may be a bargain. Some may require a bit of TLC with Deoxit spray to clean tarnished contacts, and then you may have a very fine professional grade instrument you could never have afforded when new. But NEVER buy one where you can't find the maintenance / repair manual online. And be aware that in order to repair an oscilloscope, you need one that works...

I have seen nice analog scopes for $100-$200 plus shipping, which looked promising and like a bargain.

AVOID buying used digital scopes. Their "repair" procedure is to change whole PCBs. Which is not economically viable even if you could get the spare parts. I once threw away one of the first LeCroy digital scopes because I could not repair it. I paid the stunning price of $1 for it when the company threw it out. My loss was not so much the $1 but the many hours of my precious RQLT which were wasted on the futile attempt to fix it.

Also AVOID buying used high-end oscilloscopes of any kind. These are very complex instruments with many 1000's of components inside, which all worsen with age, and they are very complex to diagnose and repair.

- Uncle Bernie

softwarejanitor wrote:

softwarejanitor wrote:

The Hantek scope arrived today.  I've been playing with it a little.  It seems like it should work fine.  I need to learn how to use it.  I haven't used a scope much since college, mostly the Tektronix and HP units they had in labs on campus.  Those things were a lot simpler. In those days a 20MHz dual channel scope was

I never had access to a scope until I bought my own, but it only took me 10-20 minutes of youtubing to have basic enough proficiency to check a clock speed, wave form, etc. (the basics). I am usually a reading learner, but for something like this, it helps if someone shows me what I can ignore at first and what's actually fundamentally important to start, and that doesn't always come across in a user manual.