want to buy a handheld oscilloscope

[Quack]

Hi,

I am looking to buy a handheld oscilloscope.
A while back i was playing with someone elses, i dont remember the
brand, but it had 'clamp' things which meant you didnt have to make
contact with a bare wire to take readings.. i thaught that was great!.
Is that a normal function ?

I dont really know anything about oscilloscopes, i have never really
used one. But i will need one soon .

Could someone recommend one to me that comes at a decent price ?

Thanks in advance,

Alex.

 

[Rich Webb]

On 11 Sep 2003 07:09:55 -0700, alex@vuetec.com (Quack) wrote:

Hi,

I am looking to buy a handheld oscilloscope.
A while back i was playing with someone elses, i dont remember the
brand, but it had 'clamp' things which meant you didnt have to make
contact with a bare wire to take readings.. i thaught that was great!.
Is that a normal function ?

Yes but typically those are current probes. That's appropriate (and
necessary) for some applications but not all.

I dont really know anything about oscilloscopes, i have never really
used one. But i will need one soon .

Need for what?

Could someone recommend one to me that comes at a decent price ?

Repeat this three times every morning:
"FIRST the requirements and THEN the design."

There are some small, low frequency 'scopes that are kind of graphical
add-ons to multimeters. Something like
http://www.web-tronics.com/hanheloson26.html

Then there are ones like this from Tek
http://www.tek.com/site/ps/0,,3M-10566-INTRO_EN,00.html

and I'm sure there are others that reach up in both price and
capability.

Does it NEED to be hand-held or is it OK if it's just portable and
battery powered? How about small and portable but runs off mains power?

FIRST the requirements and THEN the design.

--
Rich Webb Norfolk, VA

 

[Harvey White]

On 11 Sep 2003 07:09:55 -0700, alex@vuetec.com (Quack) wrote:

Hi,

I am looking to buy a handheld oscilloscope.
A while back i was playing with someone elses, i dont remember the
brand, but it had 'clamp' things which meant you didnt have to make
contact with a bare wire to take readings.. i thaught that was great!.
Is that a normal function ?

No, if it is measuring voltage, then it has to pierce the insulation
to get a contact. If you 're looking at current, then the probe is a
current transformer (rather expensive, too...).

I dont really know anything about oscilloscopes, i have never really
used one. But i will need one soon .

If you are sure that you want one, and if the specs are good enough
(since I do not know what you wish to do with it). You might want to
try the Velleman-10 model at www.allelectronics.com Go to test
equipment, and it should be there, if they still have them. Roughly
159.00 USD plus shipping.

It is digital, it is hand held, it is single channel, and 5MHz at the
most bandwidth.

Could someone recommend one to me that comes at a decent price ?

Since I don't know what you consider to be a decent price... Can't
say.


I will say that handheld/portable tends to be more expensive than a
bench top scope.

Harvey

Thanks in advance,

Alex.

 

[Quack]

Hi people,

Sorry for my silly question ... I thaught if i say too much it would
make it even more obvious how little i actually know about this stuff

But here goes, i'll try and explain the kind of thing i want todo ..

What i want to do is see a reading of signals from things like optical
sensors and digital outputs from various things ..
I could do this with a multimeter if the signal was there for any
decent amount of time ..
But as i *think*, an oscilloscope can help me here to 'slow down' time
and see what is going on ?

So im interested in getting a little graphical graph displaying
voltage over time, for use in low current digital circuits. 0v-12v
max.

For example;

An optical sensor mounted on something and a wheel with a hole in it,
spinning infront in such a way that on only ONE part of the wheel
where the hole is the optical sensor would be triggered (or
untriggered, whichever) .. how can i SEE that the sensor did infact
work ...

The way i accomplish this kind of stuff at the moment is to
incorporate the sensor into a circuit (amplification where needed) and
program a PIC chip to wait for the 'high' or 'low' (whatever the case
might be) and light an LED for say 100ms, so i can see a flash .. a
funny way todo things very difficult to find problems when they
occur ...

So really it does not need to sample anything faster than a PIC chip
would operate, as that is pertty much all i work with.
Of course PIC chips range in their speed, depending on how fast you
run them, but i run them at 4 or 8 mhz tops.

I am looking at getting a "Velleman HPS10"
(http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2557720053&category=4677),
this has a 10mhz processor built in, does this mean i can read samples
upto 10 mhz ? so this would suite my needs of operating with PIC chips
at 4-8 mhz ?

For this kind of usage, are the clamps useless ?
If not, then can i use any brand of 'clamps' on this HPS10 unit ?


Thanks for your help!



Alex.



"Walter Harley" <walterh@cafewalter.com> wrote in message news:<vm1ma7837jt34f@corp.supernews.com>...

"Quack" <alex@vuetec.com> wrote in message
news:47057cc1.0309110609.571911ec@posting.google.com...
[...]
I dont really know anything about oscilloscopes, i have never really
used one. But i will need one soon .

Could someone recommend one to me that comes at a decent price ?


What will you need it for? That will help us figure out what to recommend.

 

[Rich Webb]

On 14 Sep 2003 05:44:48 -0700, alex@vuetec.com (Quack) wrote:

Hi people,

Sorry for my silly question ... I thaught if i say too much it would
make it even more obvious how little i actually know about this stuff

But here goes, i'll try and explain the kind of thing i want todo ..

What i want to do is see a reading of signals from things like optical
sensors and digital outputs from various things ..
I could do this with a multimeter if the signal was there for any
decent amount of time ..
But as i *think*, an oscilloscope can help me here to 'slow down' time
and see what is going on ?

Or, rather, think of an o'scope as a really fast voltmeter.

So im interested in getting a little graphical graph displaying
voltage over time, for use in low current digital circuits. 0v-12v
max.

For example;

An optical sensor mounted on something and a wheel with a hole in it,
spinning infront in such a way that on only ONE part of the wheel
where the hole is the optical sensor would be triggered (or
untriggered, whichever) .. how can i SEE that the sensor did infact
work ...

While I *know* that others will disagree, I'd recommend that you bite
the bullet and get a decent digital scope rather than spend $19.95 on a
third-hand, 30-year old analog scope with dodgy electronics.

Recommendation: a Tek TDS1002 or TDS1012.

It uses "real time" digital sampling. That allows you to trigger on and
capture a single event rather than relying on the repaint from a
continuous series of waveforms. Very handy when working with digital
electronics to be able to capture one particular wavetrain, e.g., one
character on a serial data line or one transition on your optical
sensor. It's nice to "know" that an event happened but it may also be
useful to know exactly how wide that one pulse was and what the rising
and falling edges look like.

I am looking at getting a "Velleman HPS10"
(http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2557720053&category=4677),
this has a 10mhz processor built in, does this mean i can read samples
upto 10 mhz ? so this would suite my needs of operating with PIC chips
at 4-8 mhz ?

You need to look at two numbers; the sample rate is one but the analog
bandwidth is equally important. That defines the characteristics of the
front-end electronics. At 2 MHz, this is at the limit of an 8 MHz PIC
(four clocks per instruction cycle, so an output port can't be toggled
faster than 2 MHz, IIRC).

A rule of thumb is that you'll want a bandwidth that's at least 5X the
target signal frequency, so at least a 10 MHz bandwidth would be
preferred. That is *not* the same as the 10 MHz sample rate (which is
how fast the internal electronics sample the incoming signal).
See also: Nyquist.

The Vellman is only a single channel. Sometimes that's OK but often
you'll want to see what's happening HERE when something changes THERE
and how long after THIS that THAT happened.

For this kind of usage, are the clamps useless ?

No, but clamps measure current whereas standard probes measure voltage.
Each has uses, but a current probe won't tell you the state of a logic
port as well as a the boring old standard probes will. Ignore the
perceived coolness factor of clamps; virtually every o'scope is supplied
with probes and not clamps because most of the time, probes are the
appropriate sensor.

--
Rich Webb Norfolk, VA

 

[Harvey White]

On 14 Sep 2003 05:44:48 -0700, alex@vuetec.com (Quack) wrote:

Hi people,

Sorry for my silly question ... I thaught if i say too much it would
make it even more obvious how little i actually know about this stuff

But here goes, i'll try and explain the kind of thing i want todo ..

What i want to do is see a reading of signals from things like optical
sensors and digital outputs from various things ..
I could do this with a multimeter if the signal was there for any
decent amount of time ..
But as i *think*, an oscilloscope can help me here to 'slow down' time
and see what is going on ?

If digital, it can work to stop it completely. One shot mode.

So im interested in getting a little graphical graph displaying
voltage over time, for use in low current digital circuits. 0v-12v
max.

For example;

An optical sensor mounted on something and a wheel with a hole in it,
spinning infront in such a way that on only ONE part of the wheel
where the hole is the optical sensor would be triggered (or
untriggered, whichever) .. how can i SEE that the sensor did infact
work ...

The way i accomplish this kind of stuff at the moment is to
incorporate the sensor into a circuit (amplification where needed) and
program a PIC chip to wait for the 'high' or 'low' (whatever the case
might be) and light an LED for say 100ms, so i can see a flash .. a
funny way todo things very difficult to find problems when they
occur ...

So really it does not need to sample anything faster than a PIC chip
would operate, as that is pertty much all i work with.
Of course PIC chips range in their speed, depending on how fast you
run them, but i run them at 4 or 8 mhz tops.

I am looking at getting a "Velleman HPS10"
(http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2557720053&category=4677),
this has a 10mhz processor built in, does this mean i can read samples
upto 10 mhz ? so this would suite my needs of operating with PIC chips
at 4-8 mhz ?

The maximum data rate that a 10 MHz sampling rate scope can tolerate
is 5 MHz, due to something called the Nyquist Theorem. I have one,
and it's good to about 2-3 Mhz in terms of what you can really see.
You must have at least one sample for a waveform's period to be able
to reproduce it, that's one down and one up...

The frequency of the PIC is the clock frequency, which you might or
might not be able to see... but the events that it generates, if at
least a microsecond pulse, will be quite visible.

For this kind of usage, are the clamps useless ?
If not, then can i use any brand of 'clamps' on this HPS10 unit ?

Any "clamp" that manages to match a 1 megohm 35pf (a standard) input
impedance. The Velleman comes with a 10x probe. It will run from 5
nicad batteries, does not have a backlight, has 2 waveform memories.

It is also available for 159.00 + 6.00 shipping from
www.allelectronics.com it's in the test equipment section, so let
that determine your maximum price.

Thanks for your help!

Harvey

Alex.



"Walter Harley" <walterh@cafewalter.com> wrote in message news:<vm1ma7837jt34f@corp.supernews.com>...
"Quack" <alex@vuetec.com> wrote in message
news:47057cc1.0309110609.571911ec@posting.google.com...
[...]
I dont really know anything about oscilloscopes, i have never really
used one. But i will need one soon .

Could someone recommend one to me that comes at a decent price ?


What will you need it for? That will help us figure out what to recommend.

 

[Quack]

Thanks guys! this cleared things up a lot ...

I will go with the cheap HPS10 for now, although the point about
multiple samples at the same time (would be great for clocked serial
data lines like SPI) is a good one .. i will consider that.

Atleast this unit will get me started, im sure i will soon want more
features soon enough though .. but i think if i get an expensive
feature packed one straight off that all these features will
overcomplicate things perhaps ...

thanks again for all your help! ,

Alex.


Rich Webb <bbew.ar@mapson.nozirev.ten> wrote in message news:<qbs8mv8efk2am5uld54f0ur92mgajc8das@4ax.com>...

On 14 Sep 2003 05:44:48 -0700, alex@vuetec.com (Quack) wrote:

Hi people,

Sorry for my silly question ... I thaught if i say too much it would
make it even more obvious how little i actually know about this stuff

But here goes, i'll try and explain the kind of thing i want todo ..

What i want to do is see a reading of signals from things like optical
sensors and digital outputs from various things ..
I could do this with a multimeter if the signal was there for any
decent amount of time ..
But as i *think*, an oscilloscope can help me here to 'slow down' time
and see what is going on ?

Or, rather, think of an o'scope as a really fast voltmeter.

So im interested in getting a little graphical graph displaying
voltage over time, for use in low current digital circuits. 0v-12v
max.

For example;

An optical sensor mounted on something and a wheel with a hole in it,
spinning infront in such a way that on only ONE part of the wheel
where the hole is the optical sensor would be triggered (or
untriggered, whichever) .. how can i SEE that the sensor did infact
work ...

While I *know* that others will disagree, I'd recommend that you bite
the bullet and get a decent digital scope rather than spend $19.95 on a
third-hand, 30-year old analog scope with dodgy electronics.

Recommendation: a Tek TDS1002 or TDS1012.

It uses "real time" digital sampling. That allows you to trigger on and
capture a single event rather than relying on the repaint from a
continuous series of waveforms. Very handy when working with digital
electronics to be able to capture one particular wavetrain, e.g., one
character on a serial data line or one transition on your optical
sensor. It's nice to "know" that an event happened but it may also be
useful to know exactly how wide that one pulse was and what the rising
and falling edges look like.

I am looking at getting a "Velleman HPS10"
(http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2557720053&category=4677),
this has a 10mhz processor built in, does this mean i can read samples
upto 10 mhz ? so this would suite my needs of operating with PIC chips
at 4-8 mhz ?

You need to look at two numbers; the sample rate is one but the analog
bandwidth is equally important. That defines the characteristics of the
front-end electronics. At 2 MHz, this is at the limit of an 8 MHz PIC
(four clocks per instruction cycle, so an output port can't be toggled
faster than 2 MHz, IIRC).

A rule of thumb is that you'll want a bandwidth that's at least 5X the
target signal frequency, so at least a 10 MHz bandwidth would be
preferred. That is *not* the same as the 10 MHz sample rate (which is
how fast the internal electronics sample the incoming signal).
See also: Nyquist.

The Vellman is only a single channel. Sometimes that's OK but often
you'll want to see what's happening HERE when something changes THERE
and how long after THIS that THAT happened.

For this kind of usage, are the clamps useless ?

No, but clamps measure current whereas standard probes measure voltage.
Each has uses, but a current probe won't tell you the state of a logic
port as well as a the boring old standard probes will. Ignore the
perceived coolness factor of clamps; virtually every o'scope is supplied
with probes and not clamps because most of the time, probes are the
appropriate sensor.

 

[Theo Markettos]

Rich Webb <bbew.ar@mapson.nozirev.ten> wrote:

For this kind of usage, are the clamps useless ?

No, but clamps measure current whereas standard probes measure voltage.
Each has uses, but a current probe won't tell you the state of a logic
port as well as a the boring old standard probes will. Ignore the
perceived coolness factor of clamps; virtually every o'scope is supplied
with probes and not clamps because most of the time, probes are the
appropriate sensor.

Also bear in mind that, unless things have improved a lot recently, clamps
are designed for high current work. So they're really for measuring
currents of many amps, whereas digital logic is likely to be at microamps or
lower. You're not going to be able to measure that without a lot of added
noise messing up your signal.

The main reason for clamps is to prevent you having to interrupt the supply
to insert an ammeter (you wouldn't want to rewire your electric cooker just
to measure its current consumption, for example). But voltage measurement
(usually) doesn't require breaking the circuit anyway, so this defeats the
main advantage of the clamp.

Theo

--
Theo Markettos theo@markettos.org.uk
Liphook, Hampshire, UK theom@chiark.greenend.org.uk
http://www.markettos.org.uk/

 

[Jim Yanik]

Theo Markettos <theom+news@chiark.greenend.org.uk> wrote in
news:ROu*bcx2p@news.chiark.greenend.org.uk:

Rich Webb <bbew.ar@mapson.nozirev.ten> wrote:
For this kind of usage, are the clamps useless ?

No, but clamps measure current whereas standard probes measure
voltage. Each has uses, but a current probe won't tell you the state
of a logic port as well as a the boring old standard probes will.
Ignore the perceived coolness factor of clamps; virtually every
o'scope is supplied with probes and not clamps because most of the
time, probes are the appropriate sensor.

Also bear in mind that, unless things have improved a lot recently,
clamps are designed for high current work. So they're really for
measuring currents of many amps, whereas digital logic is likely to be
at microamps or lower. You're not going to be able to measure that
without a lot of added noise messing up your signal.

The main reason for clamps is to prevent you having to interrupt the
supply to insert an ammeter (you wouldn't want to rewire your electric
cooker just to measure its current consumption, for example). But
voltage measurement (usually) doesn't require breaking the circuit
anyway, so this defeats the main advantage of the clamp.

Theo

TEK used to make a couple of clamp-on AC current probes for small signals
and high BW,and a DC-50Mhz current probe that measured small
currents,AM503/A6302,for the TM500 mainframe,now available,IIRC,from TEGAM.

--
Jim Yanik,NRA member
jyanik@kua.net

 

[Quack]

I have another question regarding the HPS10 now,
i was reading some things about video signals, and generating them
from PIC controllers;
http://www.rickard.gunee.com/projects/video/pic/howto.php

im just wondering if this oscilliscope will be fast enough to capture
the scan lines of a PAL video signal ? 64us long.

Alex.


Harvey White <madyn@ix.netcom.com> wrote in message news:<ih62mv4nv6ean3ieojhbnddl9u1qn5tk1v@4ax.com>...

On 11 Sep 2003 07:09:55 -0700, alex@vuetec.com (Quack) wrote:

Hi,

I am looking to buy a handheld oscilloscope.
A while back i was playing with someone elses, i dont remember the
brand, but it had 'clamp' things which meant you didnt have to make
contact with a bare wire to take readings.. i thaught that was great!.
Is that a normal function ?

No, if it is measuring voltage, then it has to pierce the insulation
to get a contact. If you 're looking at current, then the probe is a
current transformer (rather expensive, too...).


I dont really know anything about oscilloscopes, i have never really
used one. But i will need one soon .

If you are sure that you want one, and if the specs are good enough
(since I do not know what you wish to do with it). You might want to
try the Velleman-10 model at www.allelectronics.com Go to test
equipment, and it should be there, if they still have them. Roughly
159.00 USD plus shipping.

It is digital, it is hand held, it is single channel, and 5MHz at the
most bandwidth.


Could someone recommend one to me that comes at a decent price ?

Since I don't know what you consider to be a decent price... Can't
say.


I will say that handheld/portable tends to be more expensive than a
bench top scope.

Harvey



Thanks in advance,

Alex.

 

[Harvey White]

On 24 Sep 2003 04:26:03 -0700, alex+google@vuetec.com (Quack) wrote:

I have another question regarding the HPS10 now,
i was reading some things about video signals, and generating them
from PIC controllers;
http://www.rickard.gunee.com/projects/video/pic/howto.php

im just wondering if this oscilliscope will be fast enough to capture
the scan lines of a PAL video signal ? 64us long.

640 samples at 10 megasamples/second.

I'm not too sure how it will look on the color signals, but it will
capture the line.

Harvey

Alex.


Harvey White <madyn@ix.netcom.com> wrote in message news:<ih62mv4nv6ean3ieojhbnddl9u1qn5tk1v@4ax.com>...
On 11 Sep 2003 07:09:55 -0700, alex@vuetec.com (Quack) wrote:

Hi,

I am looking to buy a handheld oscilloscope.
A while back i was playing with someone elses, i dont remember the
brand, but it had 'clamp' things which meant you didnt have to make
contact with a bare wire to take readings.. i thaught that was great!.
Is that a normal function ?

No, if it is measuring voltage, then it has to pierce the insulation
to get a contact. If you 're looking at current, then the probe is a
current transformer (rather expensive, too...).


I dont really know anything about oscilloscopes, i have never really
used one. But i will need one soon .

If you are sure that you want one, and if the specs are good enough
(since I do not know what you wish to do with it). You might want to
try the Velleman-10 model at www.allelectronics.com Go to test
equipment, and it should be there, if they still have them. Roughly
159.00 USD plus shipping.

It is digital, it is hand held, it is single channel, and 5MHz at the
most bandwidth.


Could someone recommend one to me that comes at a decent price ?

Since I don't know what you consider to be a decent price... Can't
say.


I will say that handheld/portable tends to be more expensive than a
bench top scope.

Harvey



Thanks in advance,

Alex.

 

[Quack]

Hi Harvey,

It just arrived a couple of hours after posting my message! .
After unpacking it, i plugged it to the first signal i could find, a
color video camera (PAL) and went through the booklet learning its
functions.

At the same time i was reading a webpage describing what a PAL video
signal looks like, so i could compare what readings i got, and what im
supposed to get/look for.

I could get a clear picture of the scan lines, one after the other,
all exactly 64us long(4us-sync,8us-color burst, 52us-signal) but i
could not get the vertical sync's.

I played around with triggering a little bit, assuming i just couldnt
see them because it was all too fast, still, i cant find them. What
method should i be using to find such a portion of a signal ? is there
a particular technique ?considering there is a very repetetive signal
inbetween (ie: the scan lines).

Other than that, having never really used an Oscilloscope before, i
can definantly say this one is easy to use and understand.

Thanks again,

Alex.

Harvey White <madyn@ix.netcom.com> wrote in message news:<r0d3nv44rd5gfabpq2miqsm7idmslgotd6@4ax.com>...

On 24 Sep 2003 04:26:03 -0700, alex+google@vuetec.com (Quack) wrote:

I have another question regarding the HPS10 now,
i was reading some things about video signals, and generating them
from PIC controllers;
http://www.rickard.gunee.com/projects/video/pic/howto.php

im just wondering if this oscilliscope will be fast enough to capture
the scan lines of a PAL video signal ? 64us long.

640 samples at 10 megasamples/second.

I'm not too sure how it will look on the color signals, but it will
capture the line.

Harvey


Alex.


Harvey White <madyn@ix.netcom.com> wrote in message news:<ih62mv4nv6ean3ieojhbnddl9u1qn5tk1v@4ax.com>...
On 11 Sep 2003 07:09:55 -0700, alex@vuetec.com (Quack) wrote:

Hi,

I am looking to buy a handheld oscilloscope.
A while back i was playing with someone elses, i dont remember the
brand, but it had 'clamp' things which meant you didnt have to make
contact with a bare wire to take readings.. i thaught that was great!.
Is that a normal function ?

No, if it is measuring voltage, then it has to pierce the insulation
to get a contact. If you 're looking at current, then the probe is a
current transformer (rather expensive, too...).


I dont really know anything about oscilloscopes, i have never really
used one. But i will need one soon .

If you are sure that you want one, and if the specs are good enough
(since I do not know what you wish to do with it). You might want to
try the Velleman-10 model at www.allelectronics.com Go to test
equipment, and it should be there, if they still have them. Roughly
159.00 USD plus shipping.

It is digital, it is hand held, it is single channel, and 5MHz at the
most bandwidth.


Could someone recommend one to me that comes at a decent price ?

Since I don't know what you consider to be a decent price... Can't
say.


I will say that handheld/portable tends to be more expensive than a
bench top scope.

Harvey



Thanks in advance,

Alex.