I'd have a hard time doing a lot of what I do with an analog scope. I
have a lot of logic running at high frequency, and find myself
triggering on single pulse events that happen infrequently. The
advanced triggering options of digital scopes make seeing these events
possible. Just the pulse width, or runt pulse triggering is worth the
price when you need it. (If you need it, that is).
I've owned some low end test equipment over the years. I always end up
selling it off to upgrade to an agilent or tek product. That being
said, even the low end Tek's have problems. I have a 200Mhz digital
unit here that likes to cross talk a lot between channels. If I have a
100Mhz digital on one channel and analog on the other, A LOT of
digital will make it onto the analog trace (disconnect the channe, or
unhook the probe and the problem goes away). I'm guessing some of the
cheap scopes may exhibit this also, but have no experience first hand.
My higher end Tek scope is much better in this respect. But then
again, it's several times the cost of this 200Mhz low end tek...
FYI: I have an Agilent signal generator that's getting close to 10
years old now. Last year they replaced a bad encoder on the front
panel and did a NIST calibration on the unit free of charge. I figured
at that age, I'd have to do the work myself. The tech on the phone
spent the time to figure out what I was fixing, and looked up the unit
and notified me of the free repair option. They knew the encoder was
bad, and offered the service when I called to order a replacement
encoder. I'll keep this in mind when I buy more equipment this year.
Dan
On 4/16/2012 3:30 PM, time-nuts-requ...@febo.com wrote:
Measurement accuracy is a ruse, IMO. I don't care if a 'scope is
"accurate". I want the waveform to be a faithful representation of the
electrical behaviour of the circuit, free oif sampling artifacts and
aliasing.
If I want to accurately measure a voltage, I'll use a differential
comparator or DVM. Anything timing, an appropriately gated counter.
Some years ago Tektronix had a digital camera package with RS-170 output
and some aardvaark frame grab board for a PC and a SW package. It was
designed to do waveform measurement.
I would actually like to know why many seem to feel that a 500 MHz analog
'scope is not "good enough" for what you really do in your lab?
The more I hear about 40 GSps or whatever 'scopes, the more I'm convinced
it's like comparing car engines or top speed. So, I have a car that'll do
160 MPH and yours will do 172? So what? Can you use it? No.
YMMV,
-John
Best Wishes,
Marv Gozum, Philadelphia Pa
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