Author Topic: Can anybody explain me really how do works the time base of HP scopes 1740A and  (Read 10845 times)

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Offline SAUL BRITTO

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New photo that I think has 12 cycles:
« Last Edit: February 29, 2016, 04:00:34 am by SAUL BRITTO »
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Offline rf+tech

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Saul,

The photo actually shows 12.5 cycles across 10 divisions.

Look at the time marks at the arrows added to your photo.

RF+ Tech
 

Offline SAUL BRITTO

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rf+tech about that your equation I did P= V.t
P= 24000000 x 0.00005= 1200 is it right? IF IT IS NOT RIGHT I see at least a 12 ratio,then on the anterior image there is an error of 5 cycles to more. Right?
« Last Edit: February 29, 2016, 04:48:12 am by SAUL BRITTO »
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Offline SAUL BRITTO

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Saul,

The photo actually shows 12.5 cycles across 10 divisions.

Look at the time marks at the arrows added to your photo.

RF+ Tech

Then I have to count that half cycle on the begin and on the end,how can I fix this rf+tech?
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Offline SAUL BRITTO

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Looks like after the sweep vernier fix it is a bit better.
« Last Edit: February 29, 2016, 04:20:30 am by SAUL BRITTO »
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Offline SAUL BRITTO

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I  am reading about this calibration but I still don't have a time marker,can I fix this problem with frequency counter and a good function generator?
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Offline rf+tech

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Saul,

Before jumping into sweep calibration, it is best to know some details about the accuracy of available signals.

What is the source of the 24 MHz signal? How accurate is this signal? Is it crystal controlled?

And the same about your function generator - how accurate is this? Is it synthesized or free running? Do you have a frequency counter?

Also, I see from your posts that you are having difficulty measuring time with an oscilloscope. What is to the left of the first vertical line is not counted.

Go back to the 24 MHz signal as shown in the photo with red arrows.
Position the bottom peak of the first cycle exactly on the first vertical display line.
Move the vertical position up so the bottom peaks are on the center line.
Count 12 bottom peaks and read the scale.
From the photo, this looks like 9.5 or 9.6 divisions.
How many divisions do you measure?
Now turn the sweep vernier from right to left.
Do you see many more cycles?
Turn the sweep vernier to the right (CAL position).
Does bottom peak 12 return to the same position?

RF+ Tech
 

Offline SAUL BRITTO

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Ok I will do it.
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Offline SAUL BRITTO

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Saul,

Before jumping into sweep calibration, it is best to know some details about the accuracy of available signals.

What is the source of the 24 MHz signal? How accurate is this signal? Is it crystal controlled?

And the same about your function generator - how accurate is this? Is it synthesized or free running? Do you have a frequency counter?

Also, I see from your posts that you are having difficulty measuring time with an oscilloscope. What is to the left of the first vertical line is not counted.

Go back to the 24 MHz signal as shown in the photo with red arrows.
Position the bottom peak of the first cycle exactly on the first vertical display line.
Move the vertical position up so the bottom peaks are on the center line.
Count 12 bottom peaks and read the scale.
From the photo, this looks like 9.5 or 9.6 divisions.
How many divisions do you measure?
Now turn the sweep vernier from right to left.
Do you see many more cycles?
Turn the sweep vernier to the right (CAL position).
Does bottom peak 12 return to the same position?

RF+ Tech

Yes it is a crystal controlled oscillator.
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Offline SAUL BRITTO

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I have done these adjustments and got it better,but when a change the sweep time see small differences:
http://i65.tinypic.com/2z80vp3.jpg
« Last Edit: March 02, 2016, 05:42:58 am by SAUL BRITTO »
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Offline SAUL BRITTO

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1uSEC  I use 1mhz, 10uSEC 100KHZ and so on but,when I change the time to a near time I see that it does not keep completely stable there is a small difference
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Offline SAUL BRITTO

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I'm dabbing ice with this FG.
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Offline SAUL BRITTO

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I figure out my FG is deffective,seems a PS problem.
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Offline SAUL BRITTO

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Bingo! A cap in leackage and that a leakage wow!!!
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Offline SAUL BRITTO

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rf+tech what is the nomenclature for trigger offset on the HP scopes?
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Offline SAUL BRITTO

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rf+tech I have new photos and show you later.
« Last Edit: March 02, 2016, 09:15:40 am by SAUL BRITTO »
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Offline SAUL BRITTO

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I have done some comparisons with a tek 2220 that I have on the bench and they are very very near.
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Online tggzzz

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Saul, you might find https://entertaininghacks.wordpress.com/library-2/good-questions-pique-our-interest-and-dont-waste-our-time-2/ helps you in the long term. Not all of the points apply to you, of course!

Do keep asking good questions. But this forum isn't twitter (as in https://www.google.co.uk/search?q=define:twit ).
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline SAUL BRITTO

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I apologize if I made a mistake or bothered in any way but, I'm new in the forum and really need some warnings. But, how to discuss an issue?
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Online tggzzz

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I apologize if I made a mistake or bothered in any way but, I'm new in the forum and really need some warnings. But, how to discuss an issue?
No problem at all; no apologies necessary. You are honestly trying to learn, and that is good. The reason for pointing to that link is to help you get better answers.

Minor point: learn how to use the "quote" button, so people can understand what you are replying to.

More important point: think before posting, and where appropriate follow some of the guidelines noted on that page. Note that I don't always follow them!
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline SAUL BRITTO

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I apologize if I made a mistake or bothered in any way but, I'm new in the forum and really need some warnings. But, how to discuss an issue?
No problem at all; no apologies necessary. You are honestly trying to learn, and that is good. The reason for pointing to that link is to help you get better answers.

Minor point: learn how to use the "quote" button, so people can understand what you are replying to.

More important point: think before posting, and where appropriate follow some of the guidelines noted on that page. Note that I don't always follow them!

Thank you for your advice, was not my intention to cause this kind of event. I will be ever grateful when you advice me about my fails. I confess that I am still a little confused about the right way to act in the forum, will try to improve every day.
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Online tggzzz

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I apologize if I made a mistake or bothered in any way but, I'm new in the forum and really need some warnings. But, how to discuss an issue?
No problem at all; no apologies necessary. You are honestly trying to learn, and that is good. The reason for pointing to that link is to help you get better answers.

Minor point: learn how to use the "quote" button, so people can understand what you are replying to.

More important point: think before posting, and where appropriate follow some of the guidelines noted on that page. Note that I don't always follow them!

Thank you for your advice, was not my intention to cause this kind of event. I will be ever grateful when you advice me about my fails. I confess that I am still a little confused about the right way to act in the forum, will try to improve every day.

As I told my daughter, "let's make new mistakes".

Do continue posting and asking questions!
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline SAUL BRITTO

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I apologize if I made a mistake or bothered in any way but, I'm new in the forum and really need some warnings. But, how to discuss an issue?
No problem at all; no apologies necessary. You are honestly trying to learn, and that is good. The reason for pointing to that link is to help you get better answers.

Minor point: learn how to use the "quote" button, so people can understand what you are replying to.

More important point: think before posting, and where appropriate follow some of the guidelines noted on that page. Note that I don't always follow them!

Thank you for your advice, was not my intention to cause this kind of event. I will be ever grateful when you advice me about my fails. I confess that I am still a little confused about the right way to act in the forum, will try to improve every day.

As I told my daughter, "let's make new mistakes".

Do continue posting and asking questions!
  :-DD

Ok thx.
« Last Edit: March 03, 2016, 04:31:12 am by SAUL BRITTO »
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