The Modern Oscilloscope - Embedded.com

The Modern Oscilloscope

Sixty years ago Tektronix introduced their first product, the model 511 oscilloscope. Not just a knock-off of some standard scope design like the ones complacent Dumont were marketing, the 511 was the first scope with triggered sweep. This product launched both Tek and the modern scope.

We take triggering for granted today, but not so long ago inexpensive scopes didn't have it. In the 60s my dad took a home-ed electronics class from Devry in which he assembled a combination scope/VTVM (Vacuum Tube VoltMeter ” the “Fluke” of the era), which he passed on to me while I was in 8th grade. Untriggered, it simply kept sweeping the beam, synchronized to nothing. As I recall a “sync” knob varied the time base to stabilize ” somewhat ” the display, but that meant it was tough or impossible to measure time with much accuracy.

Howard Vollum designed Tektronix's first scope in 1946 but it was impractically large, being spread out over an entire workbench. He and machinist Milt Brave redesigned the unit, releasing it as the 511 in 1947.

Though sold as a portable unit it weighed in at a backbreaking 50 pounds. It offered 10 MHz bandwidth, though “MHz” wasn't used in this country then so the data sheet specified bandwidth in “MC” or “mc” for megacycles. Fastest sweep rate was a blinding .1 usec/division.

There's a good picture of the unit here: http://www.geocities.com/r_corriveau/500/511.html#tline . The design presaged the modern oscilloscope in a way; in the 50s Tek's wildly-popular 500 series, and then later the 7000 series in the 60s, sported a modular design where the scope had one or more plug-in modules. Big holes in the instruments' chassis were filled with vertical and/or horizontal units of differing specifications. That fad died out; today, as in 1947, scopes generally don't have plug-ins.

The unit cost $795 in 1947 dollars, or about $7300 at today's rates. That seems a bargain when you consider that it was a high-performance, highly-innovative product that had little direct competition. Today the company's TDS6000 series can price out at more than $100k.

I can't find a manual for the 511, but one for its immediate successor, the 511A ” with schematics! – is here: http://bama.edebris.com/manuals/tek/511aearly/ . A rough count identifies about 33 vacuum tubes, of which only two are twin triodes. 13 of those are in the power supply, so the scope's “smarts” use only about 22 active elements! In modern terms, 22 transistors. No multicore. No DSP.

Those tube engineers sure were great designers.

A decade later Tek's extremely popular 545 had a mere 102 tubes, yet offered so much performance that that series was still in use 30 years later.

The company sold $27K worth of 511's in 1947, growing by an order of magnitude the following year. Today they're a billion dollar company. There's little loyalty to companies anymore, but many old-timers still fondly recall their experiences with Tek's products.

Me, I worked with the 7000 series in the 70s, instruments that were just a delight to use. Small illuminated interlocked buttons and selector switches with perfect detents were magnificently fitted to human hands. I had an ancient 545 that never failed ” I never even changed a tube. But around 1990 it had been sitting neglected for a long time. No one wanted it and I junked the thing. Now it's a museum piece.

What was your experience with early scopes?

Jack G. Ganssle is a lecturer and consultant on embedded development issues. He conducts seminars on embedded systems and helps companies with their embedded challenges. Contact him at . His website is .


Wow … another trip down memory lane!

In the 1980's, There were some tools I used very heavily.

– Tek's 465B scope

– Nohau 8051 emulator

– IBM PC

– Fluke DMM

You can check out the picture of the Tek 465B here

I cut my teeth on:

– TM5000 mainframe

– TM7000 mainframe

– Tek 500 series scope

In graduate school I used a Tektronix Model 31 calculator! Betcha didn't know that Tek made these eh?

When I was a summer intern at the Signetics corporation, I programmed using a Tektronix 4010 Computer Graphics Terminal. here is a picture of this fine instrument! In fact, the above URL shows it still in use today.

There are many fine old Tektronix products being used to this day!

– Ken Wada


I've got a 465 on my workbench now. We have better ones that I can borrow if I need them, but this still handles most of my needs.

– Steve Wheeler


My Dad had one of those old, round-tube 'scopes. It was a Heathkit.

Truly amazing what we take for granted today, wondering how we ever got along without it.

I recall early “storage” scopes with persistent phosphors that allowed the electron beam to “paint” the trace onto the screen, where it would stay, along with any other traces that came along, until you pressed the ERASE button which flashed the entire screen, wiping it clean. The nicer scopes could be configured to do this erase step automatically.

And then, how did you get that waveform into your engineering notebook? Why, you free-hand drew it, of course! Later on, there were cameras that mounted to the front of the 'scope, with a shroud that covered the whole screen and blocked out ambient light. Then, you snapped a photo of the trace, and pasted it into your notebook!

Today, you just configure the built-in web server (what 'scope doesn't have that?) and point a browser at it.

– Daniel Daly


I “built” my own oscilloscope with Sanyo Dot Matrix LCD controlled through an 8051 microcontroller. Finding it hard to integrate an A/D, i used a PIC microcontroller with built-in ADC to sample the input signal and send digitized data over UART to the 8051!!! you can imagine the sweep rate; i could only see 50 Hz signals. interesting thing is i implemented the trigger in software! it almost worked. before i could refine the monster i had to join my graduate classes for computer engineering where i learn graph theory and other abstract things. Gone are the good old days.

– Muhammad Bilal


In about 1990 I acquired a 1950's Cossor scope for the princely sum of ten pounds (USD20) … still working 40 years later, and we're talking about a piece of kit made with huge beer-bottle valves, carbon composition resistors, and oil-and-paper capacitors. The insides (yes, of course I opened it up as soon as I got it) were a hand-crafted work of art. Sadly, it finally died and it was too big and heavy to keep. The crap those poor engineers had to work with! We really are spoilt these days – modern components are ultra-reliable but most modern products still fall apart after six months; frankly, I think this is shameful. How many iPods do you think will still work in 2047? We all whinge and moan about shrinking development cycles and market pressures, but we engineers choose to comply and are ultimately responsible.

– Tony Weir


My first scope was a dual-channel Cossor 1049 which I swapped for a fishing rod in 1972 when I was 16 and still at school. It was a 75lb (39kg) behemoth with a blue dual-beam CRT, a complement of 22 valves, and a vertical bandwidth of 100kHz.

My mum was terrified of it as it was a bit tempramental and I ran it (in my bedroom of course) without covers and with a suitably worded danger sign attached.

I don't know when it was made but it's successor using miniature valves (the Cossor 1035) was being advertised in the UK magazine Wireless World in June 1950.

It had a triggered timebase which I think possibly calls into question Jack's claim that Tektronix invented that feature in 1947.

There is a web page devoted to the Cossor 1049 (which includes a downloadable manual) here:

http://www.thevalvepage.com/testeq/cossor/1049/1049.htm

I used the Cossor 1049 at home for many years (while using a the classic Tek 465 at work) and eventually gave it to a radio amateur around 1985.

– Ken Mardle


I acquired a working Tek model 514 from a retired radio tech, plus original manual and full schematics. I had to replace one HV cap and clean several pots and switches. I counted 49 tubes!It's not in general use (too large!) so I use a Tek 561B (a hybrid), but it has bad ch1 and ch2 gain pots – looking fo replacements.

– Roger Jones

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