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Quick Calibration Question.

Eric
 

As I have a backlog of plugins to calibrate, I have a questions I cant seem to find a good answer too. When calibrating a scope. Is the reference the center of the graticule line, the bottom edge, or the top edge. Common since tells me it should be the center of the graticule is the alignment point. But I am hoping to confirm. Or am I asking my analog scopes to be a little too accurate?

ArtekManuals
 

Unless your scopes have a numerical readout  (many do) yes your rearranging the deck chairs on the Titanic IMO. I always try to center the trace on the graticule. But in reality you put the t5race on top of the line or under it as long as you that same point of reference when making measurements , i.e . if you calibrated with the trace above the graticule then when you go up say three divisions it is to "top" of that division line not centered

Hope that made sense

Dave

On 3/13/2020 12:03 AM, Eric wrote:
As I have a backlog of plugins to calibrate, I have a questions I cant seem to find a good answer too. When calibrating a scope. Is the reference the center of the graticule line, the bottom edge, or the top edge. Common since tells me it should be the center of the graticule is the alignment point. But I am hoping to confirm. Or am I asking my analog scopes to be a little too accurate?

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Eric
 

Nah the ones I am working on are 7000 Series. So nothing but scale readout. and yea it made scene. consistency is the impotent part.

On 3/13/2020 12:10 AM, ArtekManuals wrote:
Unless your scopes have a numerical readout  (many do) yes your rearranging the deck chairs on the Titanic IMO. I always try to center the trace on the graticule. But in reality you put the t5race on top of the line or under it as long as you that same point of reference when making measurements , i.e . if you calibrated with the trace above the graticule then when you go up say three divisions it is to "top" of that division line not centered

Hope that made sense

Dave

On 3/13/2020 12:03 AM, Eric wrote:
As I have a backlog of plugins to calibrate, I have a questions I cant seem to find a good answer too. When calibrating a scope. Is the reference the center of the graticule line, the bottom edge, or the top edge. Common since tells me it should be the center of the graticule is the alignment point. But I am hoping to confirm. Or am I asking my analog scopes to be a little too accurate?


 

Hi Eric,
If the service manual doesn't explicitly say or if there is no picture
indicating what to use I would recommend the center graticule line as the
reference since non-linear and geometric distortion would increase as you
went further above or below the center horizontal graticule line.

On the other hand it is possible that the service manual doesn't specify one
because it doesn't matter.

Dennis Tillman W7pF

On 3/13/2020 12:03 AM, Eric wrote:
As I have a backlog of plugins to calibrate, I have a questions I
cant seem to find a good answer too. When calibrating a scope. Is the
reference the center of the graticule line, the bottom edge, or the
top edge. Common since tells me it should be the center of the
graticule is the alignment point. But I am hoping to confirm. Or am I
asking my analog scopes to be a little too accurate?
--
Dennis Tillman W7PF
TekScopes Moderator

Chuck Harris
 

I think I know what you are asking, but not completely sure.

The scopes are generally specified to be in calibration only
in the center region of the CRT. For instance, the 2465 family
says between the second, and 10th graticule line horizontally,
and the second and 6th graticule line vertically.

The reason for this is there is some serious work done to fight
the electron beams natural desire to see a spherical screen,
rather than a flat screen.

Also, there is often confusion about what part of the lit phosphor
is the part from which to measure.

The trace is an embodiment of a probability "bell curve". The
center is where most of the electrons hit the phosphor screen, and
towards the outside is where some noise deflected electrons hit.

It is best practice to consider the brightest, most central part
of the width of the beam to be the "trace"... So, when making a
peak-to-peak measurement, it will be from brightest to brightest...
not from furthest most visible fuzz to furthest most visible fuzz.

-Chuck Harris

Eric wrote:

As I have a backlog of plugins to calibrate, I have a questions I cant seem to find a good answer too. When calibrating a scope. Is the reference the center of the graticule line, the bottom edge, or the top edge. Common since tells me it should be the center of the graticule is the alignment point. But I am hoping to confirm. Or am I asking my analog scopes to be a little too accurate?



Eric
 

Thanks for this Sir this was exactly what I was looking for. Also good to know that the tubes arnt specked for full screen width and true spec is a reduced graticule size.

On 3/13/2020 10:33 AM, Chuck Harris wrote:
I think I know what you are asking, but not completely sure.

The scopes are generally specified to be in calibration only
in the center region of the CRT. For instance, the 2465 family
says between the second, and 10th graticule line horizontally,
and the second and 6th graticule line vertically.

The reason for this is there is some serious work done to fight
the electron beams natural desire to see a spherical screen,
rather than a flat screen.

Also, there is often confusion about what part of the lit phosphor
is the part from which to measure.

The trace is an embodiment of a probability "bell curve". The
center is where most of the electrons hit the phosphor screen, and
towards the outside is where some noise deflected electrons hit.

It is best practice to consider the brightest, most central part
of the width of the beam to be the "trace"... So, when making a
peak-to-peak measurement, it will be from brightest to brightest...
not from furthest most visible fuzz to furthest most visible fuzz.

-Chuck Harris

Eric wrote:
As I have a backlog of plugins to calibrate, I have a questions I cant seem to find a good answer too. When calibrating a scope. Is the reference the center of the graticule line, the bottom edge, or the top edge. Common since tells me it should be the center of the graticule is the alignment point. But I am hoping to confirm. Or am I asking my analog scopes to be a little too accurate?