scope probes
 

"Swells8044" wrote in message
...
I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is
appreciated.

Depends on what you plan to be looking at.

For audio, you can probably get away with whatever wire you have around, but
don't try to do any critical measurements.

For RF or digital work, no, you can't homebrew those probes, any more than
you can homebrew the scope itself. An oscilloscope probe is part of a
precision measurement system, and the actual requirements that it must meet,
to pass a complex signal UNDISTORTED IN ANY WAY, are TOUGH.

Last time I bought probes, commodity probes were running around forty bucks
each, new. And worth it. Real Tektronix probes, new, will cost you a LOT
more, and they're worth every penny.

"Swells8044" wrote in message
...
I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is
appreciated.

Depends on what you plan to be looking at.

For audio, you can probably get away with whatever wire you have around, but
don't try to do any critical measurements.

For RF or digital work, no, you can't homebrew those probes, any more than
you can homebrew the scope itself. An oscilloscope probe is part of a
precision measurement system, and the actual requirements that it must meet,
to pass a complex signal UNDISTORTED IN ANY WAY, are TOUGH.

Last time I bought probes, commodity probes were running around forty bucks
each, new. And worth it. Real Tektronix probes, new, will cost you a LOT
more, and they're worth every penny.

In article , Swells8044
says...

I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is appreciated.
Steve

For audio? Maybe. For anything higher, definitely not. Good O-
scope probes (thinking Tektronix here) are made with a high degree of
precision, and outstanding quality in materials. This is not something
that can be duplicated at home without investing a small fortune in
specialized manufacturing equipment.

You're far better off picking up some surplus Tektronix probes at
whatever ham swap meet or electronic surplus place is local to you.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
"Quando Omni Flunkus Moritati" (Red Green)

In article , Swells8044
says...

I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is appreciated.
Steve

For audio? Maybe. For anything higher, definitely not. Good O-
scope probes (thinking Tektronix here) are made with a high degree of
precision, and outstanding quality in materials. This is not something
that can be duplicated at home without investing a small fortune in
specialized manufacturing equipment.

You're far better off picking up some surplus Tektronix probes at
whatever ham swap meet or electronic surplus place is local to you.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
"Quando Omni Flunkus Moritati" (Red Green)

I heartily endorse what the others have said about scope probes. And
there is a big difference between Tek probes and commodity probes. A
quick Web search shows this is an 80 MHz scope, so a good probe will be
necessary if you want to get the most out of it. A lot of Tek probes
show up on eBay. They're pretty rugged, so your chances of getting a
good one are probably better than for a lot of other electronic
equipment. Check your scope's input capacitance, and make sure the probe
you get is compatible with it. You should be able to find input C specs
for most common probes on the probe manufacturer's web site or elsewhere
on the Web. If this is a two-channel scope, it's a very good idea to get
two probes of the same type and cord length. You might want an
additional probe for the external trigger. This one can be lower quality
without having a big impact.

Roy Lewallen, W7EL

Swells8044 wrote:
I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is appreciated.
Steve

I heartily endorse what the others have said about scope probes. And
there is a big difference between Tek probes and commodity probes. A
quick Web search shows this is an 80 MHz scope, so a good probe will be
necessary if you want to get the most out of it. A lot of Tek probes
show up on eBay. They're pretty rugged, so your chances of getting a
good one are probably better than for a lot of other electronic
equipment. Check your scope's input capacitance, and make sure the probe
you get is compatible with it. You should be able to find input C specs
for most common probes on the probe manufacturer's web site or elsewhere
on the Web. If this is a two-channel scope, it's a very good idea to get
two probes of the same type and cord length. You might want an
additional probe for the external trigger. This one can be lower quality
without having a big impact.

Roy Lewallen, W7EL

Swells8044 wrote:
I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is appreciated.
Steve

Steve,
I don't like to disagree with the other folks on here, but IMO you can
make a bloody good probe yourself. You'll also learn a lot more than
just going out and buying one. Try this link for starters.
http://www.emcesd.com/1ghzprob.htm
HTH, Symsx.

(Swells8044) wrote in message ...
I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is appreciated.
Steve

Steve,
I don't like to disagree with the other folks on here, but IMO you can
make a bloody good probe yourself. You'll also learn a lot more than
just going out and buying one. Try this link for starters.
http://www.emcesd.com/1ghzprob.htm
HTH, Symsx.

(Swells8044) wrote in message ...
I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is appreciated.
Steve

From a brief look at the referenced web site, it looks like the author
did a decent job of making a low impedance probe. It should work quite
well if carefully constructed.

But it's actually a lot easier to make a good 50 - 1000 ohm probe (which
the web site describes) than a 10 meg probe. A 10 meg, 10X probe is a
lot more useful for most everyday measurements, which is why it's
universally used on scopes up to several hundred MHz. At least as
important as the high resistance is the relatively low capacitance it
presents to the measured circuit. (A good low Z probe has considerably
less capacitance yet, so it's a better choice at really high
frequencies. It's also fine for probing in 50 ohm environments.)

Making a good 10 meg probe is quite an art as well as a science. If you
ever disassemble an old Tek probe, one of the first things you'll notice
is the coax. It's specially made with a resistive center conductor to
damp reflections, and lossy dielectric to reduce piezoelectric and
triboelectric effects. (If you don't know what these are, connect a
piece of regular RG-58 to your scope input, turn the sensitivity up, and
flex it or rap it with a mallet.) Another tough problem is "hook", a
nonlinear property of many capacitors, dielectrics like PC board
material, and even resistors. This creates funny, hook-shaped step
responses (which is how it got its name), that are difficult or
impossible to compensate. You probably won't see hook at 50 ohm levels,
but it's pervasive in high impedance environments. The little circuit
board in the scope compensation box is likely a specially-made low-hook
expoxy glass formulation, or an inherently low-hook dielectric like
polysulfone. And both the capacitors and resistors were carefully chosen
and specified for low hook and other nonlinear properties.

A cheap or homebrew 10 meg probe is fine if you don't really care if
what you see on the scope looks like the real signal. Or if the
amplitude of a sine wave is really what the scope says it is. But if you
do, you need a decent probe.

Roy Lewallen, W7EL

Symon wrote:
Steve,
I don't like to disagree with the other folks on here, but IMO you can
make a bloody good probe yourself. You'll also learn a lot more than
just going out and buying one. Try this link for starters.
http://www.emcesd.com/1ghzprob.htm
HTH, Symsx.

(Swells8044) wrote in message ...

I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is appreciated.
Steve

From a brief look at the referenced web site, it looks like the author
did a decent job of making a low impedance probe. It should work quite
well if carefully constructed.

But it's actually a lot easier to make a good 50 - 1000 ohm probe (which
the web site describes) than a 10 meg probe. A 10 meg, 10X probe is a
lot more useful for most everyday measurements, which is why it's
universally used on scopes up to several hundred MHz. At least as
important as the high resistance is the relatively low capacitance it
presents to the measured circuit. (A good low Z probe has considerably
less capacitance yet, so it's a better choice at really high
frequencies. It's also fine for probing in 50 ohm environments.)

Making a good 10 meg probe is quite an art as well as a science. If you
ever disassemble an old Tek probe, one of the first things you'll notice
is the coax. It's specially made with a resistive center conductor to
damp reflections, and lossy dielectric to reduce piezoelectric and
triboelectric effects. (If you don't know what these are, connect a
piece of regular RG-58 to your scope input, turn the sensitivity up, and
flex it or rap it with a mallet.) Another tough problem is "hook", a
nonlinear property of many capacitors, dielectrics like PC board
material, and even resistors. This creates funny, hook-shaped step
responses (which is how it got its name), that are difficult or
impossible to compensate. You probably won't see hook at 50 ohm levels,
but it's pervasive in high impedance environments. The little circuit
board in the scope compensation box is likely a specially-made low-hook
expoxy glass formulation, or an inherently low-hook dielectric like
polysulfone. And both the capacitors and resistors were carefully chosen
and specified for low hook and other nonlinear properties.

A cheap or homebrew 10 meg probe is fine if you don't really care if
what you see on the scope looks like the real signal. Or if the
amplitude of a sine wave is really what the scope says it is. But if you
do, you need a decent probe.

Roy Lewallen, W7EL

Symon wrote:
Steve,
I don't like to disagree with the other folks on here, but IMO you can
make a bloody good probe yourself. You'll also learn a lot more than
just going out and buying one. Try this link for starters.
http://www.emcesd.com/1ghzprob.htm
HTH, Symsx.

(Swells8044) wrote in message ...

I was given a BK1570a scope but I need probes can these be homebrewed?Im a
newby to scopes so this is a learn as you go project.Any help is appreciated.
Steve