Re: [Emc-users] Measuring Noise - Oscilloscope

[John Thornton]

I was just curious not needing to compare.

On 1/1/2016 5:26 PM, Ben Potter wrote:
>> From: John Thornton [mailto:j...@gnipsel.com]
>> If you have limit switches set them up to home also, saves time when
> firing up as last offsets are still good. Also the soft limits work when you
> home. Got a photo of the el cabinet?
>> JT
> I'm not sure which version of the bridgeport you've got - but I have a
> converted Interact - with the Heidenhain control package. Are pictures of
> that conversion useful?
>
> Ta
> Ben
>
>
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Re: [Emc-users] Measuring Noise - Oscilloscope

[Gene Heskett]

On Friday 01 January 2016 18:33:32 Bertho Stultiens wrote:

> On 01/02/2016 12:27 AM, andy pugh wrote:
> >>> I'm assuming using a scope is the right way to do it?
> >>
> >> Yes and no. It depends on what you are tracking and how it is
> >> induced.
> >
> > Also, there is no way to detect an occasional microsecond spike
> > without recording and analysing unfeasible quantities of data.
> >
> > I tried looking for noise on my system with a scope, but soon gave
> > up.
>
> Indeed, transients are nearly impossible to track. A scope is fine for
> recurring signals, but terrible at finding that one-off spike that
> throws your system into neverneverland.

I could argue that when the scope is both digital and very wide band.

You can set the triggering voltage 10% above the logic 1, or 10% below 
ground, then set it for a sweep everytime its triggered.  Capture one, 
or a few thousand of those bits of noise, and analyze/measure them at 
your leasure.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Measuring Noise - Oscilloscope

[Ben Potter]

From: andy pugh [mailto:bodge...@gmail.com] 
> On 1 January 2016 at 23:21, Bertho Stultiens  wrote:
>>> I'm assuming using a scope is the right way to do it?
>> Yes and no. It depends on what you are tracking and how it is induced.
>Also, there is no way to detect an occasional microsecond spike without
recording and analysing unfeasible quantities of data.
>I tried looking for noise on my system with a scope, but soon gave up.

On the other hand, some types of failure are super obvious with a scope. 

On the level of 'Aiee! My resolvers look like that! Aie!' obvious.
Which, to continue a theme, turned out to be due to wiring. (in particular,
no problems when moving over =/- 1mm, spiky noise when moving over +/- 10mm)

It's a useful tool - which often can't help diagnose subtle and intermittent
errors. Well, not without a crazy amount of logging as per atp's post.

As daft as it sounds - nearly every significant problem I've had to date on
both my hobby level systems (gecko or clone) or my industrial systems (up to
a 30 kw servo) has been traced to a poorly specified cable. Shielding is
awesome...

>atp

Ben


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Re: [Emc-users] Measuring Noise - Oscilloscope

[Bertho Stultiens]

On 01/02/2016 12:27 AM, andy pugh wrote:
>>> I'm assuming using a scope is the right way to do it?
>> Yes and no. It depends on what you are tracking and how it is induced.
> Also, there is no way to detect an occasional microsecond spike
> without recording and analysing unfeasible quantities of data.
> 
> I tried looking for noise on my system with a scope, but soon gave up.

Indeed, transients are nearly impossible to track. A scope is fine for
recurring signals, but terrible at finding that one-off spike that
throws your system into neverneverland.


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Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Measuring Noise - Oscilloscope

[andy pugh]

On 1 January 2016 at 23:21, Bertho Stultiens  wrote:

>> I'm assuming using a scope is the right way to do it?
>
> Yes and no. It depends on what you are tracking and how it is induced.

Also, there is no way to detect an occasional microsecond spike
without recording and analysing unfeasible quantities of data.

I tried looking for noise on my system with a scope, but soon gave up.

-- 
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Measuring Noise - Oscilloscope

[Ben Potter]

> From: John Thornton [mailto:j...@gnipsel.com] 
> If you have limit switches set them up to home also, saves time when
firing up as last offsets are still good. Also the soft limits work when you
home. Got a photo of the el cabinet?
> JT

I'm not sure which version of the bridgeport you've got - but I have a
converted Interact - with the Heidenhain control package. Are pictures of
that conversion useful?

Ta
Ben


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Re: [Emc-users] Measuring Noise - Oscilloscope

[Ben Potter]

> From: Mark Johnsen [mailto:m...@ijohnsen.com] 
> John,
> Thanks for the direction, I'll look at that for the limits.  My machine is
the _one_ switch type for limits on both ends without a home.  I didn't
setup a home, but after using the mill for the last year, probably a good
idea.
> I have been running 2.6.11 on a different harddrive, so good when I need
to go.
> I do think I'll buy that O-scope, only because I've always wanted one and
it seems like that one is a decent enough hobby scope for someone like me...

I haven't heard a bad review of the Rigol scopes, for the price. I've been
tempted many a time to replace my salvaged Tektronix scope with a Rigol -
mainly for the DSO capabilities (and the overclocked firmware options).

Note, I've seen a lot of good reviews - but I tend to pay more attention to
the bad ones.

> Regards,
> Mark
> > Mark,
> > The short answer is replacing the limit/home switch wiring with shielded
cable and grounding it to one place was the difference in making the sserial
errors go away. Unless you need 2.7 back up to 2.6 till you get rid of the
> > sserial errors.
> > JT

Good to know John - I missed that from the previous thread - it's odd how
often cable standard/layout causes odd issues


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Re: [Emc-users] Measuring Noise - Oscilloscope

[Bertho Stultiens]

On 01/01/2016 11:28 PM, Mark Johnsen wrote:
> Anyway, I've been reading all the posts here and on the IRC as I've been
> away for X-mas Holiday and I think I would like to be able to measure the
> noise to be able to determine if my changes make an effect.  I've
> unsuccessfully dealt w/ noise issues before and find it a daunting task to
> trouble shoot.

Noise problems are the most difficult to trace because the source(s) can
be very obscure.

>From the current thread(s) of discussion it seems clear that there is a
lot of confusion. I may add, as a relatively experienced EE/CS guy, I
have a hard time once in a while wrapping my head around noise problems.
Having high power systems combined with low power control systems makes
it only harder.

It seems appropriate to make how-and-why-to-connect list and a checklist
of do's and don'ts added with a structured guide how to track problems.
I have to think a bit about that, but it seems a reasonable thing to do.
However, it may not be finished overnight and input is welcome.


> I'm assuming using a scope is the right way to do it?

Yes and no. It depends on what you are tracking and how it is induced. A
scope may actually worsen or remove the problem under certain
circumstances because the scope influences the system. That is what
makes it so hard to track.


-- 
Greetings Bertho

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Re: [Emc-users] Measuring Noise - Oscilloscope

[John Thornton]

If you have limit switches set them up to home also, saves time when 
firing up as last offsets are still good. Also the soft limits work when 
you home. Got a photo of the el cabinet?

JT

On 1/1/2016 5:01 PM, Mark Johnsen wrote:
> John,
>
> Thanks for the direction, I'll look at that for the limits.  My machine is
> the _one_ switch type for limits on both ends without a home.  I didn't
> setup a home, but after using the mill for the last year, probably a good
> idea.
>
> I have been running 2.6.11 on a different harddrive, so good when I need to
> go.
>
> I do think I'll buy that O-scope, only because I've always wanted one and
> it seems like that one is a decent enough hobby scope for someone like me...
>
> Regards,
> Mark
>
> Mark,
>
> The short answer is replacing the limit/home switch wiring with shielded
> cable and grounding it to one place was the difference in making the
> sserial errors go away. Unless you need 2.7 back up to 2.6 till you get
> rid of the sserial errors.
>
> JT
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Re: [Emc-users] Measuring Noise - Oscilloscope

[Mark Johnsen]

John,

Thanks for the direction, I'll look at that for the limits.  My machine is
the _one_ switch type for limits on both ends without a home.  I didn't
setup a home, but after using the mill for the last year, probably a good
idea.

I have been running 2.6.11 on a different harddrive, so good when I need to
go.

I do think I'll buy that O-scope, only because I've always wanted one and
it seems like that one is a decent enough hobby scope for someone like me...

Regards,
Mark

Mark,

The short answer is replacing the limit/home switch wiring with shielded
cable and grounding it to one place was the difference in making the
sserial errors go away. Unless you need 2.7 back up to 2.6 till you get
rid of the sserial errors.

JT
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Re: [Emc-users] Measuring Noise - Oscilloscope

[John Thornton]

Mark,

The short answer is replacing the limit/home switch wiring with shielded 
cable and grounding it to one place was the difference in making the 
sserial errors go away. Unless you need 2.7 back up to 2.6 till you get 
rid of the sserial errors.

JT

On 1/1/2016 4:28 PM, Mark Johnsen wrote:
> I have a very similar setup to John Thornton and same noise issue w/ 2.7.3:
> Mesa 5i25/7i77
> Transformer 120vac:80Vac, rectified w/ large cap to run 3-axes West Amp
> servo's (Not sure John has this)
> GS2 Automation direct 3hp drive, powered by separate 240Vac single phase
> input.  Also, I use his serial modbus setup from the PC.
> 120Vac powering the PC (not enclosed in computer case)
>
> Anyway, I've been reading all the posts here and on the IRC as I've been
> away for X-mas Holiday and I think I would like to be able to measure the
> noise to be able to determine if my changes make an effect.  I've
> unsuccessfully dealt w/ noise issues before and find it a daunting task to
> trouble shoot.
>
> I'm assuming using a scope is the right way to do it?
>
> But I need a scope and would use it for this and some smaller circuit board
> type projects (total hack type stuff).  I've seen a lot on the rigol, but
> I've also come across a siglet that seems to be slightly better.  I read
> that readings should be 10:1 over the signal and an arduino is around 8Mhz,
> so 70Mhz is probably good enough for me.
>
> Siglent SDS1072CML 7'' TFT-LCD Display Bench-Top Oscilloscope, 70MHz
> http://www.amazon.com/Siglent-SDS1072CML-TFT-LCD-Bench-Top-Oscilloscope/dp/B00GQNNHJG
>
> Wondering if anyone has an opinion on that one?  Seems like it would fit
> the bill for a low end O-scope?
>
> Here's the standard Rigol DS-1052E
> http://www.amazon.com/Rigol-DS1052E-Digital-Channels-sampling/dp/B003MYND5A
>
> Thanks,
> Mark
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