Topics

TDS3000B calibration

 

Why am I thinking of running a calibration? The trigger point is not
indicated correctly for faster signals - if I feed it a "fast rise" pulse
from the CG551AP, the trigger point is shown at about the 2% point of the
step signal even though the trigger is set to 50%. There a few other
things that weren't quite "on the mark" that I noticed as I ran through the
Training Manual. I'm hoping a calibration will sort all this out.

Timebase though appears "spot on" which is good. Is it possible to skip
steps in the calibration - no point re-doing the timebase calibration if it
is right ...

Before I attempt to run the full calibration procedure on my TDS3000B, I
want to be sure that I can generate all the necessary signals, and that the
nature of the signals is clearly called out in the calibration process once
it starts running.

I have SG503, SG504, CG551AP, and a CG5001 (with pulse heads for the last
two).

Cheers
David

 

Bump?

David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C.
Partridge
Sent: 16 March 2020 11:28
To: TekScopes
Subject: [TekScopes] TDS3000B calibration

Why am I thinking of running a calibration? The trigger point is not
indicated correctly for faster signals - if I feed it a "fast rise" pulse
from the CG551AP, the trigger point is shown at about the 2% point of the
step signal even though the trigger is set to 50%. There a few other
things that weren't quite "on the mark" that I noticed as I ran through the
Training Manual. I'm hoping a calibration will sort all this out.

Timebase though appears "spot on" which is good. Is it possible to skip
steps in the calibration - no point re-doing the timebase calibration if it
is right ...

Before I attempt to run the full calibration procedure on my TDS3000B, I
want to be sure that I can generate all the necessary signals, and that the
nature of the signals is clearly called out in the calibration process once
it starts running.

I have SG503, SG504, CG551AP, and a CG5001 (with pulse heads for the last
two).

Cheers
David

David Kuhn
 

Bump? I am following your TDS3000 thread with great interest as I am a
huge fan of this series of oscilloscopes (even though I teethed on the old
round tube 500 series in Electronics Institute in the late '70s and use to
owned one (although I could not tell you which one anymore). The TDS3000
series is the most productive and makes the most money for the user, scope
ever released by any company.

Dave

On Fri, Mar 20, 2020 at 11:28 AM David C. Partridge <
@perdrix> wrote:

Bump?

David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David
C.
Partridge
Sent: 16 March 2020 11:28
To: TekScopes
Subject: [TekScopes] TDS3000B calibration

Why am I thinking of running a calibration? The trigger point is not
indicated correctly for faster signals - if I feed it a "fast rise" pulse
from the CG551AP, the trigger point is shown at about the 2% point of the
step signal even though the trigger is set to 50%. There a few other
things that weren't quite "on the mark" that I noticed as I ran through the
Training Manual. I'm hoping a calibration will sort all this out.

Timebase though appears "spot on" which is good. Is it possible to skip
steps in the calibration - no point re-doing the timebase calibration if it
is right ...

Before I attempt to run the full calibration procedure on my TDS3000B, I
want to be sure that I can generate all the necessary signals, and that the
nature of the signals is clearly called out in the calibration process once
it starts running.

I have SG503, SG504, CG551AP, and a CG5001 (with pulse heads for the last
two).

Cheers
David




benj3867
 

Looking at the service manual for the TDS3000B, and the specs of the recommended Wavetek 9500 calibrator, the signals one needs are within the following limits:
DC Voltage between 50mV and 70V, +-0.1% amplitude accuracy.
AC Sine waves between 30kHz and 80Mhz, 5mv to 5.5V pk-pk into 50 ohm, 100ppm frequency accuracy, 3% amplitude accuracy.
Fast Rise pulse: <= 1ns rise time, at least -2.2V to 0V amplitude (unloaded), repetition rate may be anything between 100Hz and 1MHz (note that any *one* value in this range is all that is needed).

 

Thank you - that's what I needed to know!

David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of benj3867 via Groups.Io
Sent: 24 March 2020 11:45
To: TekScopes@groups.io
Subject: Re: [TekScopes] TDS3000B calibration

Looking at the service manual for the TDS3000B, and the specs of the recommended Wavetek 9500 calibrator, the signals one needs are within the following limits:
DC Voltage between 50mV and 70V, +-0.1% amplitude accuracy.
AC Sine waves between 30kHz and 80Mhz, 5mv to 5.5V pk-pk into 50 ohm, 100ppm frequency accuracy, 3% amplitude accuracy.
Fast Rise pulse: <= 1ns rise time, at least -2.2V to 0V amplitude (unloaded), repetition rate may be anything between 100Hz and 1MHz (note that any *one* value in this range is all that is needed).

benj3867
 

Glad to be of service ;)

If you do go ahead with the calibration, please be kind enough to report back with more details.

amirb
 

for fast rise pulser, is it possible to use one of Leo Bodnar's? is the frequency really important?

benj3867
 

On Wed, Mar 25, 2020 at 12:43 AM, amirb wrote:


for fast rise pulser, is it possible to use one of Leo Bodnar's? is the
frequency really important?
As far as I know, the Leo Bodnar pulser operates at 10MHz which is way too fast.
The TDS3000B service manual says that the frequency should be in the range of 100Hz to 1MHz. Why would they say 100Hz to 1MHz if 100Hz to 10MHz would also work?

While the Bodnar pulser would have been perfectly fine if you were to manually check the rise time of the scope, it will almost certainly not work in the calibration process which is automatic and during which the user can not adjust anything on the scope.

BTW, a suitable fast rise pulse generator can be easily built at home following the instructions in appendix D of Linear Technology Application Note 47 by Jim Williams (easily found on the web). All you need are 3 resistors, a capacitor, and a 2N2369 transistor. You also need a very low-current 90V power supply, which you can either build using an LT1073 as shown in the same article, or simply get from your friendly local *Bay (about $5 for a "DC-DC 8-32V to 45~390V High Voltage Boost Converter").

 

Why would they say 100Hz to 1MHz if 100Hz to 10MHz would also work?
Maybe because there were none that went to 10MHz at that time - a bit like a laptop I own whose docs say it will take a maximum of 4GB, but will happily take 8GB.

David

amirb
 

On Wed, Mar 25, 2020 at 01:29 PM, David C. Partridge wrote:


Why would they say 100Hz to 1MHz if 100Hz to 10MHz would also work?
Maybe because there were none that went to 10MHz at that time - a bit like a
laptop I own whose docs say it will take a maximum of 4GB, but will happily
take 8GB.

David
exactly and also because they simply want you to use a specific equipment for the calibration.

I dont have the other tools, so I cannot do the cal on my 3054B but still I think the 10MHz pulser would work

the important thing is what is the scope trying to measure with that pulser. It is not the BW because <1ns wouldn't cut it (the scope rise time itself is rated <700ps
so the pulser should have been much faster) so maybe it is measuring overshoot (undershoot)? but they didnt specify the overshoot of the pulser...

benj3867
 

@David, @amirb, sorry to dispel your theories.

First, they did have equipment capable of producing such pulses with repetition rates well beyond 10MHz decades before the TDS3000 series was conceived.
For example, the Tektronix PG502, introduced in 1974, could produce such pulses with repetition rates up to 250MHz, and this is just off the top of my head.
Higher performing pulse generators existed well before the PG502

As for the theory that they simply wanted to use a specific calibration equipment, this also does not hold water since the recommended Wavetek 9500 can produce such pulses with a repetition rate up to 2MHz.

Finally, @amirb, you are confusing calibration with performance verification. The calibration process is not trying to measure rise-time or bandwidth because these cannot be adjusted.

In any case guys, all you need is in the manuals and spec sheets, so you don't need anybody's help, and can easily figure things out yourselves.
Good luck with your efforts!

 

Not arguing that the technology didn't exist to do that, but the standard calibration kit in the form of the CG551AP, or CG5001 top out at 100kHz for the Fast edge setting.

The PG502 is no way a fast edge pulse generator - it has a rise time of about 1nS. I've never encountered a fast edge calibrator (RT 150pS or so) that did even 1MHz.

David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of benj3867 via Groups.Io
Sent: 25 March 2020 20:39
To: TekScopes@groups.io
Subject: Re: [TekScopes] TDS3000B calibration

@David, @amirb, sorry to dispel your theories.

First, they did have equipment capable of producing such pulses with repetition rates well beyond 10MHz decades before the TDS3000 series was conceived.
For example, the Tektronix PG502, introduced in 1974, could produce such pulses with repetition rates up to 250MHz, and this is just off the top of my head.
Higher performing pulse generators existed well before the PG502

As for the theory that they simply wanted to use a specific calibration equipment, this also does not hold water since the recommended Wavetek 9500 can produce such pulses with a repetition rate up to 2MHz.

Finally, @amirb, you are confusing calibration with performance verification. The calibration process is not trying to measure rise-time or bandwidth because these cannot be adjusted.

In any case guys, all you need is in the manuals and spec sheets, so you don't need anybody's help, and can easily figure things out yourselves.
Good luck with your efforts!

Egge Siert
 

Hi David,

A suggestion:

https://us.flukecal.com/products/electrical-calibration/electrical-calibrators/9500b-oscilloscope-calibrator?quicktabs_product_details=2

By the way the PG503 has < 200ps Risetimes at 250 MHz.

Greetings,

Egge Siert

 

Hmmm - I'd love one - are you paying? :)

David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Egge Siert
Sent: 26 March 2020 08:37
To: TekScopes@groups.io
Subject: Re: [TekScopes] TDS3000B calibration

Hi David,

A suggestion:

https://us.flukecal.com/products/electrical-calibration/electrical-calibrators/9500b-oscilloscope-calibrator?quicktabs_product_details=2

By the way the PG503 has < 200ps Risetimes at 250 MHz.

Greetings,

Egge Siert

 

On Wed, Mar 25, 2020 at 09:38 PM, benj3867 wrote:


Finally, @amirb, you are confusing calibration with performance verification.
To use some of your words, "you are confusing calibration with adjustment".
Obviously the word Calibration mean different things to different people.
Calibration, at least how we did it at Tek in Europe, was almost always
Performance Verification. There were even two Calibration options for customers
to choose from, PV or Adj, with different prices of course.
In the contract with our major customer it said that if a test was within 70%
of spec no action should be done. If it came out between 70 and 100% of spec
adjustment should be done. If the adjustment failed to return it to less
than 70% or couldn't be done the instrument would still Pass. In either case
it should be noted on the Certificate. And of course if the instrument was
out of spec and couldn't be brought back to within it would Fail the Calibration.

/HÃ¥kan

 

On Thu, Mar 26, 2020 at 03:48 AM, David C. Partridge wrote:


I've never encountered a fast edge calibrator (RT 150pS or so) that did even
1MHz.
Leo Bodnar's (no affiliation) fast pulse generators have 40ps max. rise time and 10 MHz repetition rate. BTW, the repetition rate is completely irrelevant for digital 'scopes.

Raymond

 

On Wed, Mar 25, 2020 at 05:35 PM, benj3867 wrote:


BTW, a suitable fast rise pulse generator can be easily built at home
following the instructions in appendix D of Linear Technology Application Note
47 by Jim Williams (easily found on the web).
It depends on what is needed. A pulse generator like John Williams' is suitable for checking or adjusting slew rate, which means maximum HF content. That is not the same as adjusting for optimum bandwidth, where a step response allows adjustment for flat frequency characteristics.
I doubt whether Jim Williams'pulser would produce satisfactory results or even work with the automatic adjustment routine for a TDS3000-series 'scope. At least, the pulse would have to be lengthened and flattened (using an airline, piece of coax or the like). For the same reasons, a PG506 works fine for adjusting the vertical amp of a 'scope (where 0.7 - 1000 ps rise time is fast enough) and the PG502, with comparable rise time isn't, because of the far less controlled waveshape of the PG502.

BTW sorry for mentioning Leo Bodnar's pulser in an earlier post. At the time, I hadn't seen that it was mentioned before.

Raymond

amirb
 

On Thu, Mar 26, 2020 at 12:54 PM, Raymond Domp Frank wrote:


On Thu, Mar 26, 2020 at 03:48 AM, David C. Partridge wrote:


I've never encountered a fast edge calibrator (RT 150pS or so) that did even
1MHz.
Leo Bodnar's (no affiliation) fast pulse generators have 40ps max. rise time
and 10 MHz repetition rate. BTW, the repetition rate is completely irrelevant
for digital 'scopes.

Raymond
If you look down this thread, I tried to say the same thing but somebody got pissed for some reason!

 

On Thu, Mar 26, 2020 at 06:17 PM, amirb wrote:


If you look down this thread, I tried to say the same thing but somebody got
pissed for some reason!
Amirb, you mean that part? I haven't read all posts. I should add that it's as irrelevant for analog 'scopes, apart from the fact that with the latter, trace intensity suffers too much at lower repetition rates because of the lower duty cycle.

Raymond

amirb
 


On Wed, Mar 25, 2020 at 09:38 PM, benj3867 wrote:


Finally, @amirb, you are confusing calibration with performance
verification.

Calibration means: first ""measuring"" a set of parameters from a standard calibration generator (rise time, DC gain, time interval, BW, etc....) and then
"adjusting" the instrument to bring those parameters within the predefined specs. Of course if the instrument
already meets the specs, you move on. So I dont think i was confusing anything with anything else...