开云体育

How limitting do you think a scope would be if it were limitted to
35 volts?

There is a PC based scope - USB interfaced, that I have been
eyeballing. It isn't cheap, around $300.00, but it is dual channel
and rated up to 60 Mhz which should be fine for me.

The real kicker that I am liking about the PC scopes is recording.
For some reason, I think that is important, not sure why, but I do ;-
)

The drawback is that voltage limit though. While most everything I
check is 5~12 volts, I have checked the output of my Stepper Driver
and that is at 41 volts.

This is the one that is being considered



Chris

On Friday 06 October 2006 06:48 pm, lcdpublishing wrote:

How limitting do you think a scope would be if it were limitted to
35 volts?

You're not. (See below.)

There is a PC based scope - USB interfaced, that I have been
eyeballing. It isn't cheap, around $300.00, but it is dual channel
and rated up to 60 Mhz which should be fine for me.

Looking at that, the big question in my mind is the software -- are you
limited to what they supply, and if so does it have to run under windoze?
That would be a definite deal-breaker for me at least. And it looks like it
"requires" w98 at least. :-(

The real kicker that I am liking about the PC scopes is recording.
For some reason, I think that is important, not sure why, but I do ;-
)

The drawback is that voltage limit though. While most everything I
check is 5~12 volts, I have checked the output of my Stepper Driver
and that is at 41 volts.

This is the one that is being considered

Looking at the specs, the input impedance is 1M ohms and under specifications
I find "max. input voltage: 30V (AC + DC)". Now, use a 10:1 probe with
that, as one might typically do with a scope, and you have a much higher
input impedance _and_ voltage range. And it appears that the probes are
included in that price, though even if they weren't I'd think that you could
use what probes you have handy.

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

Why not just get some nice 1% resistors and make a volage divider to add to the input? You could easily add an external X10 range that way.

Chris,

You can get 10:1 probes. All I've seen have a switch for selecting
times 1 or times 10. Are there probles with this scope. Most all
come with them. Also due to the high impedance of a scope input if
you do apply to larger voltages it should not damage anything, just
saturate the input.

ron


--- In Electronics_101@..., "lcdpublishing"
<lcdpublishing@...> wrote:

How limitting do you think a scope would be if it were limitted to
35 volts?

There is a PC based scope - USB interfaced, that I have been
eyeballing. It isn't cheap, around $300.00, but it is dual

channel

and rated up to 60 Mhz which should be fine for me.

The real kicker that I am liking about the PC scopes is

recording.

For some reason, I think that is important, not sure why, but I

do ;-

)

The drawback is that voltage limit though. While most everything I
check is 5~12 volts, I have checked the output of my Stepper

Driver

and that is at 41 volts.

This is the one that is being considered



Chris

On Friday 06 October 2006 08:37 pm, william.kroyer@... wrote:

Why not just get some nice 1% resistors and make a volage divider to add to
the input? You could easily add an external X10 range that way.

That's fine for DC. If there are any cables involved then you need to
compensate for AC effects as well, mostly cable capacitance. Which is what
the typical scope probe compensation adjustments are for.

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

On Friday 06 October 2006 10:48 pm, LT Ron Wright wrote:

Chris,

You can get 10:1 probes. All I've seen have a switch for selecting
times 1 or times 10. Are there probles with this scope. Most all
come with them. Also due to the high impedance of a scope input if
you do apply to larger voltages it should not damage anything, just
saturate the input.

I think it depends on what parts are connected to that input, inside the
scope. That rating is rather low, so it suggests that some semiconductor
device is the limitation there.

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

On Friday 06 October 2006 10:48 pm, Leon Heller wrote:

A second-hand analogue scope would be about the same price and would be a
lot more useful.

You're probably right about this -- I keep hearing that used Tek scopes are
showing up on ebay and similar places fairly regularly, and that would be a
better deal as far as I'm concerned.

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

On Friday 06 October 2006 11:12 pm, you wrote:

On Friday 06 October 2006 10:48 pm, Leon Heller wrote:

A second-hand analogue scope would be about the same price and would be a
lot more useful.

You're probably right about this -- I keep hearing that used Tek scopes are
showing up on ebay and similar places fairly regularly, and that would be
a better deal as far as I'm concerned.

This just showed up in the yahoo "Tekscopes" list:

"Greetings, all: I have a really nice 7704 that isn't getting used. ???I hope
someone on the list can use it. ???Excellent cosmetic and electrical
condition. ???200 mHz bandwidth. ???Asking $280 shipped and insured CONUS (it's
pretty heavy!). ???I can send you a photo if you're interested. ???Please reply
off list. ???Thanks for the bandwidth....Mike W2IY"

I don't know anything about that specific model, but I'm sure he wouldn't
mind answering a few questions about it, at
"albert prazolam" <devnull8it@...>

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

That scope is a 1972 model if anyone is interested.

Jim



"Greetings, all: I have a really nice 7704 that isn't getting used. ?I hope
someone on the list can use it. ?Excellent cosmetic and electrical
condition. ?200 mHz bandwidth. ?Asking $280 shipped and insured CONUS (it's
pretty heavy!). ?I can send you a photo if you're interested. ?Please reply
off list. ?Thanks for the bandwidth....Mike W2IY"

I don't know anything about that specific model, but I'm sure he wouldn't
mind answering a few questions about it, at "albert prazolam"
<devnull8it@...>

On Sat, 07 Oct 2006 05:48:05 +0200, James M.(Jim) Geidl <jgeidl@...> wrote:

That scope is a 1972 model if anyone is interested.
Jim

And it will outlast the velleman thing by a few decades ;-)
You'd have to ask if there are any plugins with it, since the 7704 is a plugin scope.


Anyway, i think Chris really wants a storage scope (and i would recommend it for his type of work), so the 7704 is out (at least without 7D20 plugin). Since he already had bad luck with one used scope, i reckon he doesn't want to take that risk again.

As others said standard probes will fit the velleman thing, 10:1, 100:1, even 1000:1, to increse the input range. This seems a fairly decent one for PC scope standards, with 1Gsample.
You'd have to set it up properly with a PC or laptop so it is somewhat comfortable to use.

ST

"Greetings, all: I have a really nice 7704 that isn't getting used. I hope
someone on the list can use it. Excellent cosmetic and electrical
condition. 200 mHz bandwidth. Asking $280 shipped and insured CONUS (it's
pretty heavy!). I can send you a photo if you're interested. Please reply
off list. Thanks for the bandwidth....Mike W2IY"
I don't know anything about that specific model, but I'm sure he wouldn't
mind answering a few questions about it, at "albert prazolam"
<devnull8it@...>

--- In Electronics_101@..., "Leon Heller"
<leon.heller@...> wrote:

----- Original Message -----
From: "lcdpublishing" <lcdpublishing@...>
To: <Electronics_101@...>
Sent: Friday, October 06, 2006 11:48 PM
Subject: [Electronics_101] How limitting do you think a scope would

be if it

were limitted to 35 volts?

How limitting do you think a scope would be if it were limitted to
35 volts?

There is a PC based scope - USB interfaced, that I have been
eyeballing. It isn't cheap, around $300.00, but it is dual channel
and rated up to 60 Mhz which should be fine for me.

The real kicker that I am liking about the PC scopes is recording.
For some reason, I think that is important, not sure why, but I do ;-
)

The drawback is that voltage limit though. While most everything I
check is 5~12 volts, I have checked the output of my Stepper Driver
and that is at 41 volts.

This is the one that is being considered

A second-hand analogue scope would be about the same price and would

be a

lot more useful.

Leon
--
Leon Heller, G1HSM
Suzuki SV1000S motorcycle
leon.heller@...

Exactly right! I bought a used Tektronix 485 via eBay for less money
than that and it has 350 MHz of bandwidth. No storage, no recording,
just a plain, ordinary, analog scope. But it's what I have always wanted.

Richard

Hi

I am using this exact model. It is wonderful piece of equipment and I would
suggest you to go for it. t has scope + spectrum analyzer + transient
recorder. It also let's you bring your data into excel and allows you to
take screenshots.

you may be able to use attenuation probes when it comes to measuring large
voltages. at $300 it is a steal I would suggest go for it.


Regards
Gaurav

Thanks for all the comments, suggestions and opinions.

While I agree that having a real scope is probably the best way to
go for the long term, I think having a scope that I can trust to be
accurate and working is more critical in the short term.

I bought that HP scope used on E-Bay - great price etc. I cleaned
it up, bought some probes and checked it out the best I can and
fixed a few broken dials. While it does work good sometimes on one
of the two channels, it's when it doesn't work good that screws me
up completely.

If I had the experience to know if what I am seeing is a problem
with the scope versus a problem with what I am checking, it wouldn't
matter much.

A good example of this is was when I tried to watch the output from
a stepper driver - I had everything set correctly on the scope and
video taped the display, but the display didn't make sense to anyone
else. There have been a number of times now when I have wanted to
measure something only to give up because it simply didn't "Work".

It appears that much of what I am doing and probably will continue
to do is in the realm of micros and related projects (Motion control
and so on). The fastest micro I know of that I can work with is
20mhz, so the 60mhz of this "Simulated scope" is certainly good for
the range of stuff I work with.

The recording ability is very important to me. Just having the easy
ability to take a "Screen shot" and post that image for help in
analyzing what is there is a huge benefit for a newbie like me.

As for the drawback of having to have a computer to use the scope,
well chances are really good that a computer is never more than 15
steps from where I am anywhere in the shop or office where I do all
this stuff. Heck, in the shop I have 2 computers and in the office
I have 3 (1 laptop and 2 desktops).

While I certainly do like storage and recording features, the
biggest gain for me is that I "Should" be able to trust the display.
I can't trust my real scope and that is a very bad thing :-(

Chris

Maybe you can diagnose/fix the HP scope some day with this scope.
Often you need a scope to fix a scope.
At least you will be able to compare the display and make sure if and where the HP is malfunctioning.

The biggest problem i have with the PC scopes is that usually the sampling rate is _way_ low, like a few Msamples at best. This one says it has 1Gsample, which should make a very useful scope (even comparable to Tek TDS220 maybe).
The other thing is of course the user interface. Even though i have a 19" tft mounted in the center of my electronics bench and input devices right in a drawer under the table surface i'm still not sure if i'd like a PC scope. I guess it would be OK, although i don't understand why they don't put the basic controls on the case of the PC scope. After all stuff like input attenuators really needs mechanical switches (or relays) and there seems little advantage in software control. Even if - the cost of say 3 rotary encoders and 10 pushbuttons would be minimal. Then the PC screen could just serve as display (and for advanced settings), while the basic controls of voltage and time would be analog, but what do i know...
That you have all the data immediately there in the PC without any importing, and that you get math-intensive functions (measurements, FFT) basically for free are very tempting though..

ST

HOLD YOUR HORSES!
or $.

I didn't carefully read the specs of it, it has only 50Msamples real time.
The 1Gsample is some faked-up oversampling number.

I would _NOT_ buy this scope, unless you are _sure_ 50Msamples is good enough for you.
It will be OK for most measurements, but don't expect to measure more than maybe 5Mhz, if that, single shot.
Usually when using micros you don't look at base clock signals, but instead at much lower speed outputs and communications. So for most stuff it will be enough. And for looking at clock signals, those are periodic so you get the full analog bandwidth.
Now my digital plugin (7D20) also has 40Msamples, and it is good for most work, but in the rare case that i need more i have a 7633 sitting below it that looks at and stores 100Mhz analog if i need it. I wouldn't give that away.

I thought that is to good to be true and re-read the specs....
Almost had to revise my opinion about PC scopes there, but no such luck they are still made cheaply.

Of course i have to take back my statement that this would be comparable to a TDS220, which has 1Gs if i remember right. A _real_ Gs.

ST

Horses stopped, but I had no plans of pulling the trigger right away
as I don't have the money.

I really don't understand that specification at all
though "50Msamples"

Sounds like something that someone made up to represent something.

Is it 50 million samples per second or something like that?




--- In Electronics_101@..., "Stefan Trethan"
<stefan_trethan@...> wrote:

HOLD YOUR HORSES!
or $.

I didn't carefully read the specs of it, it has only 50Msamples

real time.

The 1Gsample is some faked-up oversampling number.

I would _NOT_ buy this scope, unless you are _sure_ 50Msamples is

good

enough for you.
It will be OK for most measurements, but don't expect to measure

more than

maybe 5Mhz, if that, single shot.
Usually when using micros you don't look at base clock signals,

but

instead at much lower speed outputs and communications. So for

most stuff

it will be enough. And for looking at clock signals, those are

periodic so

you get the full analog bandwidth.
Now my digital plugin (7D20) also has 40Msamples, and it is good

for most

work, but in the rare case that i need more i have a 7633 sitting

below it

that looks at and stores 100Mhz analog if i need it. I wouldn't

give that

away.

I thought that is to good to be true and re-read the specs....
Almost had to revise my opinion about PC scopes there, but no such

luck

they are still made cheaply.

Of course i have to take back my statement that this would be

comparable

to a TDS220, which has 1Gs if i remember right. A _real_ Gs.

ST

On Sat, 07 Oct 2006 15:22:25 +0200, lcdpublishing <lcdpublishing@...> wrote:

Is it 50 million samples per second or something like that?

Yes.

That's the number of measurement points this thing takes. To properly picture a signal you need many points along it, if there aren't enough the shape will not be correct.
The 1Gs periodic thing is for repetitive signals. If you imagine a sine the scope takes say 10 points from one period, and then 10 from the next, but slightly shifted in time, and 10 from the next, again slightly shifted. In the end it puts them all together to display the one single sine. But what you really get is images from several periods. The signal better had the same shape in all periods or it won't make any sense. Of course with something that isn't repetitive the scope can't take data from the next period to throw it all together, it has to sample "real time", and that it can only do at 50M points a second.

ST

--- In Electronics_101@..., "lcdpublishing"
<lcdpublishing@...> wrote:

Horses stopped, but I had no plans of pulling the trigger right away
as I don't have the money.

I really don't understand that specification at all
though "50Msamples"

Sounds like something that someone made up to represent something.

Is it 50 million samples per second or something like that?

As Stefan points out, the 50 Msps limits the frequencies that can be
sampled. The absolute maximum signal that can be accurately sampled,
according to the Shannon Sampling Theorem, is 1/2 of the sample
frequency or about 25 MHz. And that requires that the signal be
periodic. All bets are off for one shot signals.

A square wave is composed of the fundamental frequency (let's say 100
kHz) and all of the odd harmonics clear up to daylight (a really high
frequency). To get a decent leading edge, you probably need up
through the 7th harmonic but I'm not going to do the math. So, for
the 100 kHz signal you need to accurately display 700 kHz or sample at
1.4 MHz. No problem - the box samples far faster than that.

However, when you get to frequencies above a very few MHz, the
sampling rate isn't fast enough. At some point, that is a problem
with all digital scopes.

I have often thought about buying a PC scope. One of the reasons is
that I like the idea of having a logic analyzer come along for the
ride. And for those that worry about Linux versus Windows, Bitscope
has the answer. FWIW, you can download the software and try it over
the Internet by connecting to a device back at the factory.

Anyway, I kind of like the Bitscope 310 (www.bitscope.com) but it only
samples at 40 Msps.

Richard

The sampling rates on the low-end digital scopes and pc scopes has kept me away from them. for the $300 figure that was mentioned,
you should be able to get a very good working tektronix 4xx series scope. The 465 is probably the most common, and easy to find a good working, clean unit. And as far as recording, there are camera setups just for that which are also easily obtained and used. you may wish to check out the Yahoo group "Tekscopes" for more info.

Don