What's on your test bench?

[Phil O. Sopher]

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?

 

[JW]

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?

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.

 

[Fred Bartoli]

MooseFET a écrit :

Do we also count the floor near the test bench?

On the bench I have:

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.

What? It's not calibrated in Fahrenheits?

 

[Spehro Pefhany]

[....]

LTSpice is free, and so is Gnu Octave. Why doesn't the budding designer
download a copy of each?
Yes to both of those.

Octave is a great language for quickly coding up the math of
something.

Also learn a little about gnuplot. It is great for making graphs of
things you can't do with a spread sheet.

Also you want to have a copy of the latest OpenOffice spreadsheet. It
can do really big ones and will import ASCII.

"> Octave is a great language for quickly coding up the math of

something."

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.)

George H.

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

There's also Scilab. http://www.scilab.org/ which might be easier for
Windows-based users.

 

[krw]

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?

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.

 

[JW]

I'd be interesting in hearing what sorts of problems they had, if you still
recall...

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...

mainly as an indication of, "when it's sold as busted on eBay, just
*how* busted does it tend to be?"

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:

1. Battery failures
2. Electrolytic cap failures
3. Shorted or open semiconductors in power supply circuits.
4. Oxidation of contacts.
5. 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.

 

[krw]

Agreed. I have an Extech DVM with thermocouple probe, handy for
household work and cooking, and a bench power supply, for testing
light bulbs and charging batteries. But no electronics!

Funny. I expected flak from you. ;-)

 

[krw]

The only times I do electronics at home is when I 'mistakenly' power
up a new PCB on Friday afternoon. Of course something doesn’t work,
and I know I’ll obsess about over the weekend. The easy solution is
to pack up pcb, scope and what ever else I’ll need and schlep it
home.

If necessary I just go into work over the weekend. If there is
something that really needs to be done it's no big deal.

 

[krw]

There's always LT Spice if I need an electronics fix on weekends. And
I'm only about 12 minutes from work.

I have the FPGA tools from the various manufacturers[*] loaded on my
laptop but I've never used them in anger. I'm 13 miles, half
interstate.

I plan to build a barn behind the cabin in Truckee, and I'll probably
have a lab there, so I can play with circuits on days when skiing
conditions aren't good.

Isn't that the time to read a book by the fire?


[*] Yikes, are the FPGA sales types hungry! I'm getting calls every
day from the four vendors.

 

[Jamie]

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.

You meant, COM/ACTIVEX/DCOM/OLE, correct?

 

[Pieyed Piper]

I put one of these in about every other rack.

http://www.home.agilent.com/upload/cmc_upload/E4440A_800x583.jpg

About once a week. 26GHz

 

[Jamie]

These are extremely handy:

http://www.aeroflex.com/ats/products/product/Broadband_Test/Broadband_Signal_Analyzers~540.html#

with 600 MHz recording/playback/analysis bandwidth, anywhere up to 18
GHz. But they are a bit expensive.

We have some E4440 spec ans, but mostly use the E4407B models, since
we have tons of those.

Are you trying to say I can't use my Grid Dip meter to perform that job?

 

[Pieyed Piper]

These are extremely handy:

http://www.aeroflex.com/ats/products/product/Broadband_Test/Broadband_Signal_Analyzers~540.html#

with 600 MHz recording/playback/analysis bandwidth, anywhere up to 18
GHz. But they are a bit expensive.

We have some E4440 spec ans, but mostly use the E4407B models, since
we have tons of those.

Our lab has like 40 or so similar such Items and we also use many of
their components as well.

 

[Pieyed Piper]

Are you trying to say I can't use my Grid Dip meter to perform that job?

Only if your name is Dippity Doo Dah.