Oscilloscope recommendation for automotive usage?

[Chris Wilson]

I have been using a USB scope but realise just how little I know about
scopes and feel the need to back track and get some basic general info
before committing to a costly purchase of a bench type scope. I hope
someone can find a few minutes to guide me here, please?

I have been using a Dataman USB scope
http://www.dataman.com/oscilloscopes...illoscope.html for basic automotive
diagnostic work, looking at injector and coil waveforms, reading the
outputs of cam and crank sensors, both Hall effect and magnetic, watching
thermistor voltage outputs, and looking at throttle position sensor
outputs, etcetera. It is not an automotive specific device like, for
example, some of the Picoscopes, but this has perhaps worked to my
advantage, as rather than pushing on screen menu buttons to set up scaling
automatically, I have had to think about what I am trying to measure and do
it manually. It has helped me get a basic grasp of signal levels.

I now find carrying a laptop around and the Dataman scope, making sure the
battery in the laptop doesn't go flat, being worried something's going to
get knocked on the floor, blah blah, is a PITA and would also like a bench
oscilloscope. Ideally I was asking about those with battery power options,
but I think these will be out of my price range and I will have to continue
to use a USB scope and the laptop when on the road, or inside a moving
vehicle.

I now find myself realizing just how poor my grasp of scopes in general is.
I need advice on whether I should be looking at analogue or digital bench
scopes, what bandwidth I need to look for, and how many channels I really
need. I certainly need two, but I have a Thurlby Thandar 20 MHz multiplexer
http://www.radiomuseum.org/r/thurlby...ltiplexer.html that might allow me
view multiple injector or coil patterns on a single scope input. I have
never tried it as I am told you need a scope with a degree of persistence
to use it, and I don't think a USB scope would have this? I would also like
a colour scope, to make differentiating two or more traces easier, and I
also like the USB scope for its ability to show voltage levels and things
digitally on screen. I suspect, but don't know, that these criteria will
mean I need to look at a digital scope?

Another thing I need advice on is depth of memory. I know Pico go on about
how important this is for storing enough data to find an intermittent
glitch. It's not something I have used with my Dataman USB scope, but I can
see how it would be useful for finding more obtuse issues.

Size and age of machine isn't a real issue now I have decided to consider a
bench based instrument. My budget is Ł600 UK max (about 950 US), so will
probably be looking at used stuff. I quite like vintage stuff, so am not
necessarily looking for anything on the basis of it "looking modern". I
would not want something totally irreparable though, unless it was dirt
cheap. Can anyone give me some pointers please, particularly re analogue V
digital and on screen voltage level displays?

Thanks for reading.

 

[Rich Webb]

On Fri, 2 Dec 2011 13:59:02 +0000, Chris Wilson <nospam@invalid.com>
wrote:

[snipetty snip]

I need advice on whether I should be looking at analogue or digital bench
scopes, what bandwidth I need to look for, and how many channels I really
need. I certainly need two, but I have a Thurlby Thandar 20 MHz multiplexer
http://www.radiomuseum.org/r/thurlby...ltiplexer.html that might allow me
view multiple injector or coil patterns on a single scope input. I have
never tried it as I am told you need a scope with a degree of persistence
to use it, and I don't think a USB scope would have this? I would also like
a colour scope, to make differentiating two or more traces easier, and I
also like the USB scope for its ability to show voltage levels and things
digitally on screen. I suspect, but don't know, that these criteria will
mean I need to look at a digital scope?

A digital scope will be lighter, smaller, run on a lower power, and have
more bells and whistles than a comparably priced analog model. There are
lots of dual channel, 100 MHz digitals to choose from. Past 100 MHz the
price/performance curve starts to "knee," although 200/250 BW models are
still reasonable.

Both Instek and Rigol have scopes that are good value for the money.
Browse their respective web sites for some ideas and look at
http://www.tequipment.net for a feel for prices -- I don't know of an
equivalent dealer over on your side of the pond.

One thing to keep in mind is to be cautious of are the "equivalent time"
sampling numbers; look at the "real time," "single sweep," or
"instantaneous" sample rate to get an idea of how useful it is in
capturing a single event.

Another thing I need advice on is depth of memory. I know Pico go on about
how important this is for storing enough data to find an intermittent
glitch. It's not something I have used with my Dataman USB scope, but I can
see how it would be useful for finding more obtuse issues.

A trade-off with deep memory is a lower rep rate. Some scopes let you
switch between narrow (basically one screen's width) and deep buffers. A
narrow buffer updates more often, which may sometimes be preferred.
Probably have to dig into the manuals to find out, though.

Size and age of machine isn't a real issue now I have decided to consider a
bench based instrument. My budget is Ł600 UK max (about 950 US), so will
probably be looking at used stuff. I quite like vintage stuff, so am not
necessarily looking for anything on the basis of it "looking modern". I
would not want something totally irreparable though, unless it was dirt
cheap. Can anyone give me some pointers please, particularly re analogue V
digital and on screen voltage level displays?

The other nice thing about digitals is the "free" measurement functions
that digital processing makes possible. Yes, one can always count
divisions and multiply by the scale factors but automatic measurements
sure are nice to have.

--
Rich Webb Norfolk, VA

 

[josephkk]

On Fri, 02 Dec 2011 11:59:53 -0500, Rich Webb <bbew.ar@mapson.nozirev.ten>
wrote:

On Fri, 2 Dec 2011 13:59:02 +0000, Chris Wilson <nospam@invalid.com
wrote:

[snipetty snip]
I need advice on whether I should be looking at analogue or digital bench
scopes, what bandwidth I need to look for, and how many channels I really
need. I certainly need two, but I have a Thurlby Thandar 20 MHz multiplexer
http://www.radiomuseum.org/r/thurlby...ltiplexer.html that might allow me
view multiple injector or coil patterns on a single scope input. I have
never tried it as I am told you need a scope with a degree of persistence
to use it, and I don't think a USB scope would have this? I would also like
a colour scope, to make differentiating two or more traces easier, and I
also like the USB scope for its ability to show voltage levels and things
digitally on screen. I suspect, but don't know, that these criteria will
mean I need to look at a digital scope?

A digital scope will be lighter, smaller, run on a lower power, and have
more bells and whistles than a comparably priced analog model. There are
lots of dual channel, 100 MHz digitals to choose from. Past 100 MHz the
price/performance curve starts to "knee," although 200/250 BW models are
still reasonable.

Both Instek and Rigol have scopes that are good value for the money.
Browse their respective web sites for some ideas and look at
http://www.tequipment.net for a feel for prices -- I don't know of an
equivalent dealer over on your side of the pond.

Add Owon to the list, and there is yet another one that i can't remember
right now. I believe that Saelig sells on the east side of the pond. And
some of the models include battery capability. 2 Channels 50 MHz should
be available under US$400. 4 channels 100 MHZ can be had for about
US$800-1000. Battery capability may be extra, batteries extra on top of
that. Probes may be extra. Some models may work well with true sine wave
inverters (for automotive use).

One thing to keep in mind is to be cautious of are the "equivalent time"
sampling numbers; look at the "real time," "single sweep," or
"instantaneous" sample rate to get an idea of how useful it is in
capturing a single event.

Another thing I need advice on is depth of memory. I know Pico go on about
how important this is for storing enough data to find an intermittent
glitch. It's not something I have used with my Dataman USB scope, but I can
see how it would be useful for finding more obtuse issues.

A trade-off with deep memory is a lower rep rate. Some scopes let you
switch between narrow (basically one screen's width) and deep buffers. A
narrow buffer updates more often, which may sometimes be preferred.
Probably have to dig into the manuals to find out, though.

Size and age of machine isn't a real issue now I have decided to consider a
bench based instrument. My budget is Ł600 UK max (about 950 US), so will
probably be looking at used stuff. I quite like vintage stuff, so am not
necessarily looking for anything on the basis of it "looking modern". I
would not want something totally irreparable though, unless it was dirt
cheap. Can anyone give me some pointers please, particularly re analogue V
digital and on screen voltage level displays?

The other nice thing about digitals is the "free" measurement functions
that digital processing makes possible. Yes, one can always count
divisions and multiply by the scale factors but automatic measurements
sure are nice to have.