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Barry Harvey

I Like 'Scopes

Barry Harvey
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Maciel
Maciel
8/31/2013 6:03:00 PM
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Newbie
Analog X Digital
 

Technological advancement has made him more viable to purchase digital oscilloscopes with even more features some engineers still prefer to use the analog oscilloscope, I personally do not use much, because they think they're a little slow ...

I would like to know from our readers, what type of oscilloscope and best for your applications and why?

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Barry Harvey
Barry Harvey
8/28/2013 4:58:04 PM
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Re: Analog scopes
I'm not gonna do this HP vs. Tek thing.  Not gonna.

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Navelpluis
Navelpluis
8/28/2013 4:38:45 PM
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Artist
Analog scopes
We also love our couple of analog scopes we still have around. Both are HP's 1742A I think they are born in the '70 ;-) These are the 'low power' versions with the neon bulb functions illumination, a brilliant concept. We bought them 25 years ago as surplus from the navy. They still go 100% okay. Triggering I always found fantastic, no problems at all. I also had a 2465 from Tek with that special tube, but they made the failure to skip flash in their design to hold the calibration. What a failure !! Due to time limitatins I sold it away to a good friend: He managed to go through the tedious and flakey calibration process. Tek certainly did not make a good job here. The previous than 24xx series older Tek designs I did not like too much: Lots of contact problems. Due to the custom chips often unrepairable (here in Europe), and the modular design with too tiny buttons...

Nowadays we certainly have digital scopes. I have an old LeCroy LC584AL. This one is a digital scope with amazing analog front end. Wow, what a beast, only from the fan noise you recognize it from 50 feet distance ;-) But I had amazing engineering results with this one. It calculates your brain out: Jitter from here to the moon. Beautiful. They still had their own OS, so no free storage of your measurement results at the NSA...

Another oldie I bought 10 years ago is a HP54124T, you know, the large digital scopes with a test set attached to it with a flat cable. We used this one for trace TDR measurement. Wonderful piece of equipment, would not miss that experience. Last year I saw one at the HAM fest in Friederichshafen (Germany) for 230 EURO's (about $300) At the end of the day I saw it still sitting on the stand: Nobody bought it, unbelivable...

Don't start this topic with spectrum analyzers. I know that I have a little fetish in this respect 8-)  All of the old equipment still is around in our lab. Most of the time this equipment is not in use, but from time to time I take a day to play with some of them again. Lots of fun !

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D Feucht
D Feucht
8/28/2013 12:38:27 AM
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Blogger
Tek Triggering
Barry,

Tek's triggering improved significantly over the older 545-era scheme of differentiated-edge pulse synchronization when it was replaced by ECL arm and trigger RS flops and an input gate with hysteresis. The hysteresis provides some delay time for flop setup when holdoff releases (holdoff is the inhibition of a new sweep until the trace has settled on the left side of the screen) and when the new trigger edge (from the trigger level/slope comparator) arrives. (Details on this are in my book on waveform-processing circuits at scitechpub.com ) The key problem is in deciding whether or not to run a new sweep when the holdoff releases simultaneous with a new trigger edge. Equivocation results in trace jitter on the screen.

When I was working in the Tek portable scopes group in the late '70s on the trigger IC (the Tek M202) for the 465, 475 replacements, it was able to reliably trigger (with acceptably low trace jitter) to over 350 MHz with what I recall were 7 GHz NPN BJTs. (The layout was in rubylith on large light tables!)

If you really want to get into fast 'scope details, get ahold of John Addis, who designed the 7104 vertical amplifier front end, or Audio Precision Inc. analog founder Bruce Hofer, who designed its fast time-base. Addis also invented the very fast overload-recovering vertical amplifier scheme used in Tek 'scopes nowadays. Both are up in the Beaverton area.

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RedDerek
RedDerek
8/27/2013 11:45:07 PM
User Rank
Master
Scope desires
I did enjoy the old Tek scopes with the phosphor screens. I remeber taking pictures with the polaroid camera as well. With phosphor screens going out, it might be an interesting project to tap into the X and Y drive of the screen and interpret onto an LCD screen. This would solve the bad phosphor issues.

I have traveled with the Fluke handheld scope a few times and we found that was the best scope to use when making power measurements across a 12 inch long, 1 inch diameter flash lamp. We used one channel for the differential across the lamp and the other for a current donut. Then let the scope do the math to calucalte the joules per pulse.

So, the analogs are great, but the digitals do have a good spot in my tool chest. I certainly agree that an analog could still capture somethings the digital cannot. Thus the idea of the screen conversion circuit.

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jbike
jbike
8/27/2013 9:29:23 PM
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Blogger
Re: Heavy vs Light
Well I must admit that after reading your blog I just about bid on a Tektronix 2465B oscilliscope on ebay. I may end up with one yet! I could not agree with you more about the analog scopes.

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DaeJ
DaeJ
8/27/2013 6:46:41 PM
User Rank
Master
Re: Heavy vs Light
Weight comparison is based on the almost same functionality between analog scope and digital scope.

Well, I did carry scope and test the device from place to place. Then, I realized that old scope is more weight than that of new scope (digital scope).  I knew that some engineer measure the frequency response by Ipod.  It seem like smartphone is one- size- fits- all.

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Barry Harvey
Barry Harvey
8/27/2013 6:12:46 PM
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Blogger
Re: Heavy vs Light
I dunno...I seldom lift my 'scopes.  If I were a travelling repair kind of guy, weight would matter.  Come to think of it, my Tesla S is damn heavy too but handles really well and is fast.  Reminds me of the 7104.

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DaeJ
DaeJ
8/27/2013 5:25:02 PM
User Rank
Master
Heavy vs Light
Generally speaking, analog scope is really heavy because the old components of electronic might add the weight of scope and PCB board is really big. But when I used the digital scope, it is really not heavy. Also, when checking component inside board, the component is getting small and better performance compared with old components used in the analog scope. The light weight scope is better.

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PZman
PZman
8/27/2013 3:14:27 PM
User Rank
Newbie
Re: Test vs. Design
I also grew up with the 465 with the TDR option. Also have on my bench two Sencore scopes from the 1970's. Not a lab scope but great for troubleshooting, especially tube amps.

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Page 1 / 2   >   >>
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