Why won't scope work well on car's injectors?

R

Ricky Spartacus

Guest
I'm new to an EZ oscilloscope 5020G. And disappointed to see that when
hooked to a car`s fuel injector, I can`t seem to hold the square wave
still so to measure size of the square wave. The car idles rough and
probably made the square wave drift away from the oscilloscope`s
screen slowly. Is there a way I can hold it still so I can measure the
duration of a fuel injector? Measuring the duration is important
becasue it may tell if it`s a rich or lean mixture. I`ve tried what I
can on the oscilloscope.
 
or the scope was in "auto" trigger mode. try "normal trigger" mode.

--
change .combo to .com for correct email

***************************************************
"We ought always to know precisely why a given job
is done in a particular way, and why it is done at
all, and why it can't be done more efficiently,
if it must be done at all."-- T.J.Watson

***************************************************

"Baphomet" <fandaDEATH2SPAMMERS@catskill.net> wrote in message
news:voqdptkoulnm42@corp.supernews.com...
"Ricky Spartacus" <RickySpartan@mailandnews.com> wrote in message
news:d1e1d73f.0310150354.46ff8def@posting.google.com...
I'm new to an EZ oscilloscope 5020G. And disappointed to see that when
hooked to a car`s fuel injector, I can`t seem to hold the square wave
still so to measure size of the square wave. The car idles rough and
probably made the square wave drift away from the oscilloscope`s
screen slowly. Is there a way I can hold it still so I can measure the
duration of a fuel injector? Measuring the duration is important
becasue it may tell if it`s a rich or lean mixture. I`ve tried what I
can on the oscilloscope.

You should be able to trigger the scope on the positive (or negative)
slope
of the waveform so that measuring pulse width (duration) shouldn't be a
problem. If you can't get a good internal trigger, try triggering
externally. I think you may have had the sweep in the "free running" mode.
Click to expand...
 
"Ricky Spartacus" <RickySpartan@mailandnews.com> wrote in message
news:d1e1d73f.0310150354.46ff8def@posting.google.com...
I'm new to an EZ oscilloscope 5020G. And disappointed to see that when
hooked to a car`s fuel injector, I can`t seem to hold the square wave
still so to measure size of the square wave. The car idles rough and
probably made the square wave drift away from the oscilloscope`s
screen slowly. Is there a way I can hold it still so I can measure the
duration of a fuel injector? Measuring the duration is important
becasue it may tell if it`s a rich or lean mixture. I`ve tried what I
can on the oscilloscope.
Click to expand...
You should be able to trigger the scope on the positive (or negative) slope
of the waveform so that measuring pulse width (duration) shouldn't be a
problem. If you can't get a good internal trigger, try triggering
externally. I think you may have had the sweep in the "free running" mode.
 
I tried positive, negative, norm and auto mode but maybe it requires
skill since I'm new. On the back of the scope it says, "external
trigger input." I assume I need an external trigger device? I never
seen an external trigger device. What is it?

I assume a $500 scope should be able to see a pulse width of a fuel
injector, shouldn't it? The scope is a 20MHz 2 Ch, Dual Trace &
Function Generator Model OS-5020G Manufacturer by EZ Digital (Formerly
Goldstar / LG Precision)

I will take both advice and begin twisting and turning knobs veeeryyy
slooowly.

http://www.minute-man.com/acatalog/Online_Catalog_Analog_Oscilloscopes_124.html

Thanks very much.
Rick.

or the scope was in "auto" trigger mode. try "normal trigger" mode.

--
change .combo to .com for correct email

***************************************************
"We ought always to know precisely why a given job
is done in a particular way, and why it is done at
all, and why it can't be done more efficiently,
if it must be done at all."-- T.J.Watson

***************************************************

"Baphomet" <fandaDEATH2SPAMMERS@catskill.net> wrote in message
news:voqdptkoulnm42@corp.supernews.com...

"Ricky Spartacus" <RickySpartan@mailandnews.com> wrote in message
news:d1e1d73f.0310150354.46ff8def@posting.google.com...
I'm new to an EZ oscilloscope 5020G. And disappointed to see that when
hooked to a car`s fuel injector, I can`t seem to hold the square wave
still so to measure size of the square wave. The car idles rough and
probably made the square wave drift away from the oscilloscope`s
screen slowly. Is there a way I can hold it still so I can measure the
duration of a fuel injector? Measuring the duration is important
becasue it may tell if it`s a rich or lean mixture. I`ve tried what I
can on the oscilloscope.

You should be able to trigger the scope on the positive (or negative)
slope
of the waveform so that measuring pulse width (duration) shouldn't be a
problem. If you can't get a good internal trigger, try triggering
externally. I think you may have had the sweep in the "free running" mode.
Click to expand...
 
Ricky Spartacus wrote:
I tried positive, negative, norm and auto mode but maybe it requires
skill since I'm new. On the back of the scope it says, "external
trigger input." I assume I need an external trigger device? I never
seen an external trigger device. What is it?

I assume a $500 scope should be able to see a pulse width of a fuel
injector, shouldn't it? The scope is a 20MHz 2 Ch, Dual Trace &
Function Generator Model OS-5020G Manufacturer by EZ Digital (Formerly
Goldstar / LG Precision)

I will take both advice and begin twisting and turning knobs veeeryyy
slooowly.
Click to expand...
It helps a bit if you understand what the knobs do.

Normal mode waits indefinitely for a trigger signal (that starts the
horizontal sweep of the trace) while auto times out and generates a
trace, even if there has been no trigger signal for a while. If you
are not sure if your scope is actually seeing a trigger event, Start
with auto mode, to get the trace on the screen, then switch to no
normal mode to adjust the trigger conditions. That way, even if you
don't see anything useful in the trace, you will know when the trigger
condition has been met by the flash of a trace going by.

Then you can experiment with the conditions that must be met to
produce a valid trigger event. This is where the positive/negative
going selection comes in. And also the source of the signal that is
being looked at for slope and magnitude by the trigger generator
circuit. The source choices are usually, A or B channel, the line
signal coming through the power cord, or an external signal you are
connecting to a separate connector (usually on the right side of the
front panel). If you had access to some other clean pulse signal that
had a precise timing relationship to the one you want to see, (say,
the primary of the ignition coil) you might start the trace when that
popped (via the external trigger input), and then see how long after
that channel A and/or B showed some activity.

If you want to watch channel A and trigger on the waveform you are
watching, make sure the trigger source is not set to channel B.

The filter options on the trigger signal (AC, DC, horizontal sync,
vertical sync, noise filter, etc.) just optimize the chance that you
will create a trigger event only when you want one, and not on some
other accidental part of the trigger waveform that barely happens ot
meet the trigger conditions. The DC position is usually the
unfiltered position, so start with that. If you get overlapping
traces indicating that you are triggering two different places in the
waveform, even when you sweep the trigger threshold (voltage level)
knob back and forth, then you may want ot try the noise filter
position to see if it eliminates the extra triggers.

Then, once you achieve a clean sweep that puts many copies of
essentially the same waveform on top of each other (a stable trigger),
you will need to adjust the sweep speed (seconds per CM knob) to
compress or expand the waveform to see the details in the best time
scale. Then adjust the vertical gain (volts per cm). If you are
triggering on the vertical input signal, expect ot have ot go back and
adjust the trigger threshold to compensate for the change in vertical
gain. If you are using an external trigger, adjusting the vertical
gain has no effect on the sweep trigger process.

--
John Popelish
 
Ricky Spartacus wrote:
I tried positive, negative, norm and auto mode but maybe it requires
skill since I'm new. On the back of the scope it says, "external
trigger input." I assume I need an external trigger device? I never
seen an external trigger device. What is it?

I assume a $500 scope should be able to see a pulse width of a fuel
injector, shouldn't it? The scope is a 20MHz 2 Ch, Dual Trace &
Function Generator Model OS-5020G Manufacturer by EZ Digital (Formerly
Goldstar / LG Precision)

I will take both advice and begin twisting and turning knobs veeeryyy
slooowly.

http://www.minute-man.com/acatalog/Online_Catalog_Analog_Oscilloscopes_124.html

Thanks very much.
Rick.

or the scope was in "auto" trigger mode. try "normal trigger" mode.

--
change .combo to .com for correct email

***************************************************
"We ought always to know precisely why a given job
is done in a particular way, and why it is done at
all, and why it can't be done more efficiently,
if it must be done at all."-- T.J.Watson

***************************************************

"Baphomet" <fandaDEATH2SPAMMERS@catskill.net> wrote in message
news:voqdptkoulnm42@corp.supernews.com...

"Ricky Spartacus" <RickySpartan@mailandnews.com> wrote in message
news:d1e1d73f.0310150354.46ff8def@posting.google.com...
I'm new to an EZ oscilloscope 5020G. And disappointed to see that when
hooked to a car`s fuel injector, I can`t seem to hold the square wave
still so to measure size of the square wave. The car idles rough and
probably made the square wave drift away from the oscilloscope`s
screen slowly. Is there a way I can hold it still so I can measure the
duration of a fuel injector? Measuring the duration is important
becasue it may tell if it`s a rich or lean mixture. I`ve tried what I
can on the oscilloscope.

You should be able to trigger the scope on the positive (or negative)
slope
of the waveform so that measuring pulse width (duration) shouldn't be a
problem. If you can't get a good internal trigger, try triggering
externally. I think you may have had the sweep in the "free running" mode.
Click to expand...
Do you have the trigger set to the same channel you are looking at?
They have to match before you will get a proper trigger. You also need
enough signal to make it trigger. If the signal is 0 to 12 volts, set
the scope for 2 volts per division.
--


Michael A. Terrell
Central Florida
 
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