Over a 40 year period of interest, I've gathered some test equipment, AF Genny, RF Genny, Freq Counter, High Impedance Voltmeter, Wheatstone Bridge, Oscilloscope.
None of these is particularly small and all are at least a 6" cube.
It seems to me that the same functionality could be achieved these days with perhaps just a few inches of bench space, but, would it be of any use?
The eqpt I gathered together dates very much from the days of designing circuitry with individual componenents (R, L, C, BJT) and offers test and validation at that level, but nowadays we don't work at that level (even op amps have been around for that 40 year period).
So, what do you have on your test bench these days, how big is it, did you design it yourself, and what would you recommend to the budding circuit designer of today who isn't in the industry and therefore does not have access to Spice or Matlab to validate their designs?
LTSpice is free, and so is Gnu Octave. Why doesn't the budding designer download a copy of each?
I have one 19-inch rack nearly full of aged-to-perfection high end HP and Tek gear. Not counting the Tek 11802 sampling scope (which is a special case) I paid about 2.5 cents on the dollar for it. (See the list I posted here on October 1st.)
If the budding designer can lay off beer for a month, he can have a good quality analog scope, +- variable power supply, pulse generator, DMM, and temperature-controlled soldering iron, courtesy of eBay. I'd sure have learned faster if I'd had all that stuff as a kid.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
At home: Lecroy 9374M scope Keithley 2000 DMM HP 5385A opt 004 counter Agilent 6643 power supply HP 8656B General Radio resistor decade box
Other than the decade box, all bought defective on Ebay and repaired by myself.
At Job #1 Agilent 54810A scope Valhalla 2701B DC calibrator HP 745C AC calibrator Fluke 45 DMM Philips PM 2534 DMM Some crappy old B&K power supply Fluke 9100 and various pods
At job #2 Lecroy 9354L scope Keithley 2010 DMM Kiksui 300W electronic load HP 437 Power meter HP 8350A generator with various plug-ins EIP 545 counter EDC MV106 voltage standard. Amrel +-30V 3A power supply (forget model #) HP 5005 signature analyzer Bob Parker's blue ESR meter
Don't really design anything, I'm a test equipment repair technician.
A Tek digital phosphor scope and an old-old Philips scope that is only good for 25 MHz. Both are connected to the system being developed. I need to watch signals in two unrelated time domains.
There is a Fluke 45(IIRC) DVM with RS-232 output that I can record on the PC. I need to monitor a DC voltage over the time frame of hours and I don't want to do all that writing.
The PC has 4 RS-232 ports. Two of them run to the system. (Not counting the Fluke)
Beside the PC is a laptop that is currently not in use but its serial port is the reason it is sitting there.
The power supply is a B&K.
On the floor is a shield can the size of a modest water heater.
Filed away in a cabinet is a bunch of stuff but one that comes to mind is a calibrated hair drier. The temperature of the air it puts out is just about exactly 60C.
"> Octave is a great language for quickly coding up the math of
Cool, I never heard of Octave. Steep learning curve? I've never used Matlab or similar software. When I need math functions more complicated than my calculator I fire up an old version of QuickBasic (4.5?) under DOS. I did a little bit of C coding back in the 80's, but never needed the speed, (or the slows.. I found it easier to debug the basic code.)
Octave is an open-source Matlab clone, originally developed as courseware. It has a pretty good user base and reasonable developer support. It can run most Matlab M-files unaltered. Earlier versions had trouble with plotting, but the latest ones are quite good, though not as good as Matlab. (On the other hand, they don't cost $2k.)
Octave/Matlab are matrix-oriented, so they work more efficiently with vector and matrix operations (not necessarily linear ones). They do have loops and so on, but they run at QuickBasic type speeds instead of Matlab type speeds. Octave/Matlab are nearly as fast as compiled code for vectorish stuff.
Matlab is great if you need the more advanced extensions, but paying $2k for the basic program is completely unnecessary otherwise.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
I'd be interesting in hearing what sorts of problems they had, if you still recall... mainly as an indication of, "when it's sold as busted on eBay, just
While OO is great, it also has bloat and annoyances (UI gets confused with multiple monitors). You can get Gnumeric as a great stand alone spreadsheet.
The learning curve isn't too bad. If you can do basic, you should be able to learn to use Octave.
Octave defaults to printing the results unless you put a semicolon on the end. Here's a plot of sin()
octave:1> X=3D1:0.1:6 # Make an array of 1 to 6 in 0.1 size steps octave:2> Y=3Dsin(X) # Find the sin() of each value octave:3> plot(X,Y) # Make a pretty plot
Functions are made like this:
octave:7> function Z=3DDoThing(A,B)
A B and Z are all matrix values so DoThing would add two matrixes.
Parts cabinet to the left, whiteboard to the right. Out of sight is a bunch of cables and adapters and other small test gear, DVMs and RLC meters and such. Big stuff can be wheeled up on a cart as necessary.
This is an Ikea "computer workstation" and parts cabinet.
I do a lot of live-bug breadboarding on hacked copperclad FR4 and use the Bellin SMT adapters for wiring up small stuff.
White board? This is the era of BIG LCD displays and schematic software. :P Which brings me to.. No computer monitor on the bench??? I suppose it'll get accidently poked with the soldering pen.
At home? Nothing, if you don't count a couple of Fluke-77s and a couple of HF DVMs (left visible, used as bait). I don't do electronics at home. I get enough in the 55 hours/week or so at work.
The Lecroy 9374M scope had a problem with the battery back up circuit on the CPU board. Lecroy 93XX (and possibly other Lecroy) scopes are weird in that if the rechargeable battery falls below or above a certain voltage it locks up the CPU. In fact, if you disconnect the battery when it's up and running, the scope will freeze up. (Agilent 545XX scopes also lock up when the battery dies) This particular one's voltage would surge up to almost
5V on a power-up and stay there, possibly back-feeding or latch-up from the real time clock - I found that putting a 33uF tantalum on the Vbat voltage would prevent that momentary surge. The floppy drive was also bad, I figured out how to adapt a standard slim floppy drive used in laptops to replace the oddball Epson drive.
The Keithley 2000 would fail random self tests - a power supply re-cap fixed it. I just fixed a Keithley 2001 MEM2 with the exact same issue, but that one's for sale now. I don't need that kind of accuracy, and it's missing some functions that the 2000 has.
The HP 5385A counter had a shorted over-voltage protection zener in the 5V digital supply.
The Agilent 6643 power supply had a busted LCD display. Rather than spend $85 for a new one from Agilent, I found that their 3488A switch unit shares the same display - they can be had for peanuts; nobody wants 'em it seems. After replacing the display the supply would error out in overvoltage mode when programmed to output a voltage greater than 2VDC, a bad op-amp in the sense inputs.
The HP 8656B, can't recall that one...
More often than not, much of the stuff is quite repairable as long as someone hasn't already made a mess of it in a botched repair attempt. The only piece I bought and was never able to repair is a Tek 2430A which had bad CCDs - the chips are pretty much unobtanium these days. I'd say the most likely failures are:
Battery failures
Electrolytic cap failures
Shorted or open semiconductors in power supply circuits.
Oxidation of contacts.
Mechanical failures
Working part time for one of the used test equipment companies has allowed be to gain quite a bit of experience and knowledge in certain "magic bullet" fixes. Those are fixes where a particular piece is notorious for certain failures and cures. I'm always on the lookout on Ebay for those.
I scribble the schematic of a breadboard and correct it as I go, and list measurements or notes on the whiteboard, then photograph everything... the breadboard, scope waveforms, the whiteboard. If any of it is interesting enough, we release it to an engineering notes folder on a server, or dump relevant bits into our parts database.
Some of the whiteboard pics and scope shots go directly into customer proposals. They seem to enjoy it, a break from PowerPoint.
I'll add a laptop if I'm talking to a serial box or background debugging firmware or things like that.
I don't have a lot of room - this is in the corner of my office - so I bring in equipment as needed. The big sampling scope weighs about 80 pounds, and the Mantis is bolted down, so they're permanent.
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