Scope attenuators 1,2,5, why bother?

25kHz).

Heck, then you might as well go all out and hang one of these puppies up front, along with some ECL memory:

--
Regards, Joerg

http://www.analogconsultants.com/

I did note in your post the digital display of voltage, however is that pk to pk or rms, ok probably both/either. But how much ringing is on my squarewave and how much did my snubber knock it down? Add a couple of moveable cursors to set at the difference between two points I want measured and display that difference. Up to 8 cents now, :-) Mike

John Larkin wrote in news: snipped-for-privacy@4ax.com:

21.5 yrs at TEK,I never saw a scope that had anything other than 1-2-5 for their time-bases. that included the TDS200,TDS300,500 series.

Perhaps that's some software setting for the 2.5/div TB ranges? Or the variable setting left in there by somebody? it really doesn't make any sense otherwise.

--
Jim Yanik
jyanik
at
kua.net

If there's a way to fix it, I can't find it. DEFAULT SETUP doesn't help.

John

But you didn't design that TDS220? Hopefully not ...

--
Regards, Joerg

http://www.analogconsultants.com/

25kHz).

The 4:1 demuxed output is slow enough to connect to an FPGA; you don't need ECL memory for it.

Regards, Allan

25kHz).

True. When spending hundreds of Dollars on the ADC another $100 for a zippy FPGA won't matter ;-)

--
Regards, Joerg

http://www.analogconsultants.com/

Joerg wrote in news:TFyjj.38714$ snipped-for-privacy@newssvr27.news.prodigy.net:

No,I was a tech in the Indy and Orlando Field Service Centers,repaired and calibrated analog scopes to 500Mhz,TM500,TV products. I tried out the TDS220,TDS320,and TDS540 scopes.

--
Jim Yanik
jyanik
at
kua.net

On a sunny day (Wed, 16 Jan 2008 18:38:49 -0600) it happened "amdx" wrote in :

Yep, 2 cursors is better then one, just hope I have the code space. It is getting pretty full as it is. Maybe I will indeed need an ARM....

On a sunny day (Thu, 17 Jan 2008 00:33:26 GMT) it happened Joerg wrote in :

No, Joerg I do not see this as a problem, it makes little difference, in my view, if you use a pot, or an 11 position switch that sucks anyways, because often you cannot see what range it is on, _without_ OSD.

If the pot causes the on screen display to flip between 10mV/div, 20mV/Div etc, it is exactly the same thing _without_ the need for a lot of numbers on frontpanel. Or were you referring to overload? I once killed a scope by accidently touching it to the boost (top) anode of a BW TV (10x probe, about 6kV).

I fixed it myself (Ch1) using Ch2 to see what was wrong in Ch1. (only had one scope in the repair shop).

On a sunny day (Thu, 17 Jan 2008 00:38:06 GMT) it happened Joerg wrote in :

25kHz).

That is a very nice chip, really. It will also need some very nice memory :-)

On a sunny day (Thu, 17 Jan 2008 13:45:20 +1100) it happened Allan Herriman wrote in :

Block RAM?

Demux in logic to a suitable width (perhaps 64 bits @ 375MHz), then write into block ram.

Many of the FPGA families fast enough for this work also contain fast multipliers, which would make the digital gain adjustment trivial. The ADC083000 only has 6ish ENOB, so digital gain adjust will only get you so far (i.e. you would probably need finer steps than 1,10,100 on the analog PGA).

The FPGA would be StratixII or III, Virtex4 or 5, etc. The Altera ones might be better, as they have the really large (~100k) dual port rams. Truely useful sized rams (~Mbytes) would need to be off-chip, of course.

Some of the FPGA families support PCI-e, if you wanted to get serious update rates on a plug in card for a desktop computer.

Regards, Allan

sensitivity.

OSD? Sure, but not 1.55V ...

--
Regards, Joerg

http://www.analogconsultants.com/

25kHz).

It will also require a really nice bank account ;-)

--
Regards, Joerg

http://www.analogconsultants.com/

Ah, good. Didn't want to step on anyone's toes here. I guess as a tech it must not have been too much fun repairing one of these plastic bread-box scopes.

IMHO the TDS220 (and some others) were a real disgrace for Tektronix. The first time I used one my faith in that company was shaken quite a bit. I guess they should have kept some of the older engineers.

[...]

--
Regards, Joerg

http://www.analogconsultants.com/

Joerg wrote in news:r7Mjj.36458$ snipped-for-privacy@newssvr21.news.prodigy.net:

I didn't work on the digital scopes.

the entire TDS series is module-exchange only.(I believe the modules are now repaired at Beaverton and DC service centers,the last remaining US service centers)

IIRC,TDS200s were only two boards and a display in a case. The TDS200 PS was a throwaway(purchased part),but I acquired one to play with,it was just a bad cap and diode in the backlight section.TEK didn't even have schematics for that PS. IIRC,in some spare time,I also fixed a

2430 PS for the tech that serviced that line.He had already installed a new PS,so he saved the old PS as a spare for test.

I liked working on switchers...

--
Jim Yanik
jyanik
at
kua.net

On a sunny day (Thu, 17 Jan 2008 17:14:29 GMT) it happened Joerg wrote in :

sensitivity.

etc,

Why not, it would be an incredible coincidence if it was 2.000000V ;-)

ity.

This sounds like a good idea, from the cost viewpoint; a cascade of three AGC type amplifiers (Gilbert cells) will give logarithmic gain programmed by a voltage source (8 bit DAC?). You can use a phantom input channel to feed a calibration source, to get past the thermal drift, and a sample/hold circuit to hold the gain constant during an accumulate/calibrate cycle.

But for human interface reasons, you want a human-set screen range that DOESN'T change until the human changes it. It's OK to have the internals do some gain-riding with the signal, but I'd get dizzy watching the screen readjust all the scale values in realtime.

That little grid overlay on the oscilloscope screen is a GREAT simplification for lots of uses. I'm not happy thinking I have to digitize with a cursor instead of just reading it off (no hands!).