General Oscilloscope Question

[CJT]

instantwow wrote:

I recently purchased an oscilloscope on Ebay. It is a 100Mhz model. I
was configuring the scope using the calibration output, which is a
1Khz 2 volt square wave. The horizontal line drawing on the scope
looks good, however, the vertical trace portion on this wave is barely
visible at the highest brightness setting. Is the normal, or is there
a problem with the scope? Is this common with analog scopes? This is
my first oscilloscope, so I’m not sure. Here’s a photo I took. Any
ideas?

http://www.flickr.com/photos/27262651@N04/2601539284/

Thanks.

That's exactly how it should look (although I would turn the brightness
down a bit). The amount of time the trace spends on the vertical part
of the trace is small (the beam is moving very fast) relative to the
horizontal part, so it's dimmer.

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[Jamie]

instantwow wrote:

I recently purchased an oscilloscope on Ebay. It is a 100Mhz model. I
was configuring the scope using the calibration output, which is a
1Khz 2 volt square wave. The horizontal line drawing on the scope
looks good, however, the vertical trace portion on this wave is barely
visible at the highest brightness setting. Is the normal, or is there
a problem with the scope? Is this common with analog scopes? This is
my first oscilloscope, so I’m not sure. Here’s a photo I took. Any
ideas?

http://www.flickr.com/photos/27262651@N04/2601539284/

Thanks.
That's normal for an analog display, the raise time of the

square wave is so good that it's not allowing the beam in the
CRT to stay on a section long enough to fully charge the phosphorus.

You'll find other signals that are not raising so fast like your
test signal and the vertical line will be more visible..

You can make adjustments to the settings of the CRT controls to
help you a bit on the visibility of the line. Making it brighter is
not the answer.. If the scope has a LP (Low Pass) filter option, you
may want to try that. It will remove some of the square corners from the
wave how ever, it should improve on the visible problem.

A digital scope with LCD won't react like that.


http://webpages.charter.net/jamie_5"

 

[Bill]

JMini wrote:

On 6/22/2008 2:52:30 PM, instantwow wrote:
I recently purchased an oscilloscope on Ebay. It is a 100Mhz model. I
was configuring the scope using the calibration output, which is a
1Khz 2 volt square wave. The horizontal line drawing on the scope
looks good, however, the vertical trace portion on this wave is barely
visible at the highest brightness setting. Is the normal, or is there
a problem with the scope? Is this common with analog scopes? This is
my first oscilloscope, so I’m not sure. Here’s a photo I took. Any
ideas?

http://www.flickr.com/photos/27262651@N04/2601539284/
Thanks.

It's just making the transition from 0V to 2V almost instantaneously (high
slew rate). Leaving little time for the phosphor on the screen to respond. It
looks like it's responding well.

That part has always bothered me. I have a 1990 vintage 4 channel,
100MHz, 2245 with only about 40 hours of use after 18 years, and it has
the same square wave. Having a 1KHz and a 1MHz calibration would have
been appreciated so the rise time could be checked for overshoot and
proper probe calibration for higher frequencies.
That part aside, it works like a dream since 99% of my needs are below
100MHz. It was bought for me by a company I was consulting for so I
could do more work at home and not have to be physically in their
building, but I had to pay 'income' tax on it.
I would still like to get an older 547 since that had the sharpest
display of any scope, ever.
Bill Baka