What Oscilloscope to get

I'd also consider a PC based oscilloscope - this might be a better solution, any recommendations?

to analyze correctly rs232 frames I would suggest this :

but it's rather around £250 than £75... but to analyze a rs232 comm with a tek 475 you will have some time to loose...

--
Jean-Yves.

Another vote for the LogicPort from the link above. Wonderful little device, portable, and has a built-in interpreter for serial data, with user configuration options for data bits, stop bits, parity, and polarity. The demo that runs without the device installed is the production release and gives a good idea of its capabilities.

For low priced scopes with storage, look at the Tek TDS1000/2000 series.

--
Rich Webb   Norfolk, VA

Rich Webb schrieb:

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Or maybe two scopes: the pc based for low-repetition and digital storage if needed, and the =A375 Tektronix 465 if analog performance is necessary.

Choice depends on the needs and the budget one has ;-)

hth, Andreas

it.

I got my first scope from them many years ago, a tek585a made a good room warmer too ! and several other bits.

I use a hp1740a now, (with a home made 4ghz sampling unit). I find I could do with more traces/bandwidth+storage sometimes.

depends what you want to analyse with the rs232 stuff, if you just want to look at bit levels etc or if you can bang out the same bit/byte pattern repeatedly, most scopes would do, but if you want to analyse byte streams youl need far more than a scope.

Colin =^.^=

Tell us more!

Andrew

Sure, Its quite basic, I started with this circuit but wasnt happy with it ...

although I never bothered with the delay line, and I used a DG RF mosfet for the high speed ramp. I also provided a slow speed ramp generator instead of using the scope trace output, and I used single 5v supply instaed of +-2.5v with ac coupled ip.

so I modified it, now an ECL D type flip flop with set/reset provides the trigger wich trigers upto 2ghz or more this holds itself in reset for 50ns then locks itself out for a further

50ns, (it didnt like this at first with metastable states so an LC was used to delay the feedback) so with say a 2ghz input you get a 10mhz sampling rate, this drives a high speed ramp wich is just an emitter follower and constant current source down to ground, this is tricky to get right as small ripples at the start cuase timebase distortion this is compared with a slow speed ramp by an ultra fast comparator, this locks itself out so it generates a squarewave delayed from the sampling rate signal, the differential op from the comparator drives a 4ghz sampling unit I got from ebay wich is just an SRD and 2 schotky diodes and 2 capacitors, this is much better than the diode switches but it is incredibly delicate an antiparallel schotky diode clamp is accross its input, this just drives a fast cmos op amp with a gain of 10, input attenuation is used to provide a maximum op of 2vp-p. and aprox 1:1 gain.

the timebase is variable but I have it at 500ps/div on my scope atm, the slow ramp generator is set to 2ms rate, its possible to see artifacts wich are 4ghz. the amplitude agrees with a schotky detector upto 2ghz wich is as high as I have used it so far.

Its made on 2side pcb made by guage isolated tracks. It still gets modified quite often still as I think of ways of improving it, so I havnt got a definitive circuit. I could do with a way of checking the acuracy of the trace. also its hard to probe around at 2ghz+, I generaly put smc coax sockets on the pcb at various points, and 500R from there to the point of interest.

I keep meaning to remake it with a few bells and whistles etc... the old circuit is also along side it with the same comparator driving the diode switches and the sampling unit. The SRD takes about 50ns to turn off so it is delayed considerably compared to the diode switch chanel. im also adding a prescaler on the trigger ip for my freq counter.

Atm im using it to debug a heterodyne lidar wich uses modulated laser light at 1ghz+ hopefully upto 2ghz.

Colin =^.^=

oh and the slow ramp generator inserts a neg sync pulse into the op so its easy to trigger.

Colin =^.^=