Re: [PSES] Oscilloscope probe calibration

[Doug Smith]

Hi Ed and the group,
 
If you are refering to the compensation output, it never needs to be
calibrated. Amplitude is unimportant, as is frequency as long as it is
low, 500 to 1000 Hz. The beauty of the probe cal is the generator
parameters are unimportant as long as the freq is low and the wave
looks squarish on the rise and fall times on a 1 ms/div time scale. If
you cal the probe with a 5 MHz square wave you need to know its
amplitude accurately, but not at 1000 Hz. I will cover this on the
webinar on Friday. If we overflow, I can repeat it later.
 
Doug

On Tue, 12 Jul 2016 12:55:10 -0700, Ed Price  wrote:

  I have had many occasions where I got a scope back from
metrology and they had checked the calibration of each input channel
(usually using the 50 Ohm option), always separate of the probes. But
even worse, they never seemed to check the front-panel calibration port
(they treated that just like the many ports on the rear which were
never actually calibrated or validated).
 
 
Does your current calibration source test the parameters of the front
panel calibration port? (I found it interesting that there was a trend
to de-emphasize those calibration ports, moving them to the rear or
sometimes not even having one.)
 
 
Ed Price
WB6WSN
Chula Vista, CA USA
 
 
From: Ken Wyatt [mailto:k...@emc-seminars.com]
Sent: Tuesday, July 12, 2016 9:39 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Oscilloscope probe calibration
 
 
Doug, you’re such a tease! :-)
 

___
 
 
I'm here to help you succeed! Feel free to call or email with any
questions related to EMC or EMI troubleshooting - at no obligation.
I'm always happy to help!
 

Kenneth Wyatt
Wyatt Technical Services LLC
 
56 Aspen Dr.
Woodland Park, CO 80863
 

Phone: (719) 310-5418
 
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Re: [PSES] Oscilloscope probe calibration

[Ed Price]

I have had many occasions where I got a scope back from metrology and they had 
checked the calibration of each input channel (usually using the 50 Ohm 
option), always separate of the probes. But even worse, they never seemed to 
check the front-panel calibration port (they treated that just like the many 
ports on the rear which were never actually calibrated or validated).

 

Does your current calibration source test the parameters of the front panel 
calibration port? (I found it interesting that there was a trend to 
de-emphasize those calibration ports, moving them to the rear or sometimes not 
even having one.)

 

Ed Price
WB6WSN
Chula Vista, CA USA

 

From: Ken Wyatt [mailto:k...@emc-seminars.com] 
Sent: Tuesday, July 12, 2016 9:39 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Oscilloscope probe calibration

 

Doug, you’re such a tease! :-)


___

 

I'm here to help you succeed! Feel free to call or email with any questions 
related to EMC or EMI troubleshooting - at no obligation. I'm always happy to 
help!


Kenneth Wyatt
Wyatt Technical Services LLC

56 Aspen Dr.
Woodland Park, CO 80863


Phone: (719) 310-5418


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Re: [PSES] Oscilloscope probe calibration

[Ken Wyatt]

Doug, you’re such a tease! :-)

___

I'm here to help you succeed! Feel free to call or email with any questions 
related to EMC or EMI troubleshooting - at no obligation. I'm always happy to 
help!

Kenneth Wyatt
Wyatt Technical Services LLC
56 Aspen Dr.
Woodland Park, CO 80863

Phone: (719) 310-5418

Email Me!  | Web Site 
 | Blog 
The EMC Blog (EDN) 
Subscribe to Newsletter 
Connect with me on LinkedIn 
> On Jul 12, 2016, at 10:33 AM, Douglas Smith  wrote:
> 
> Here is a bit of suspence for Friday, free webinar on this topic (joining 
> details available shortly).the addition of a simple change to the probe 
> significantly improves, almost eliminates, frequency response problems due to 
> the ground lead and circuit impedance. Can you guess what it is? Got a patent 
> on this 30+ ago while at Bell Labs, expired now  
> so in public domain. It applies to both active and 10x Hi-z passive probes 
> and is incorporated now in most high speed active probes. It can recover an 
> octave of well behaved frequency response at essentially no cost.
> 
> No spoilers from alumni of my seminars please! Will give the answer next week 
> for those that cannot make the free webinar. Just wanted to get people 
> thinking.
> 
> Doug Smith
> Sent from my iPhone
> IPhone:  408-858-4528
> Office:702-570-6108
> Email: d...@dsmith.org
> Website: http://dsmith.org
> 
> On Tue, Jul 12, 2016 at 04:17, B Rowland  wrote:
> Hello PSES crew;
> 
> 
> T Sato wrote:
> 
> > "Performance of passive probes strongly depends to the oscilloscope,
> > so I think it should always be calibrated with a specific oscilloscope
> > channel."
> 
> Indeed, not only "should", but MUST, as John Woodgate stressed.
> 
> But, as I mentioned, the calibration is often meaningless, if it does not 
> account for non-monotonic frequency response, , the Gaussian that is 
> expected, which results in unexpected transient response.
> 
> Additionally, the calibration becomes "broken" as soon as the probe/scope 
> combination is used in any "real world" application where the impedance of 
> the DUT circuit is unknown, or not the same as the calibration circuit, since 
> the probe reactive loading varies with instantaneous frequency ("typical" 500 
> MHz passive probe reaches 50 Ω loading at about 320 MHz), and the combination 
> of probe capacitance, circuit capacitance and ground lead/ground clip/ground 
> connection loop size, all cause resonances at rather common frequencies/edge 
> rates.
> 
> Probably the best 'calibration' is to attach the passive probe to a circuit 
> to be tested, and attach a low-capacitance active probe to the same point, to 
> see the "real" signal at the passive probe's tip… this could be quite a 
> surprise ;-)
> 
> In short, "Your mileage may vary" is good advice when it comes to probing
> 
> If Doug Smith does offer a webinar, please do consider attending, if you are 
> at all unsure of this whole "can of worms" that probing is!
> 
> Best regards,
> Barry Rowland
> Formerly " Senior Application Specialist, Oscilloscopes", Rohde & Schwarz 
> (and FAE at Tektronix and Agilent)
> 
> 
> 
> 
> 
> 
> On 12/07/2016, at 12:42 PM, "T.Sato"  wrote:
> 
> > On Tue, 12 Jul 2016 02:08:04 +0100,
> > John Woodgate  wrote:
> > 
> >> Slight under-compensation would cause a brief overshoot to 138 V. In my
> >> opinion, probes can't be calibrated except with the scope they are
> >> exclusively used with. Covering the cal adjuster with a sticker shows a 
> >> deep
> >> misunderstanding of how passive probes work.
> > 
> > Agreed.
> > Performance of passive probes strongly depends to the oscilloscope,
> > so I think it should always be calibrated with a specific oscilloscope
> > channel.
> > 
> > EURAMET cg-7 (calibration of oscilloscopes),
> > https://www.euramet.org/get/?tx_stag_base%5Bfile%5D=3611&tx_stag_base%5Bidentifier%5D=%252Fdocs%252FPublications%252Fcalguides%252FEURAMET_cg-7__v_1.0_Calibration_of_Oscilloscopes.pdf&tx_stag_base%5Baction%5D=downloadRaw&tx_stag_base%5Bcontroller%5D=Base
> > also says "For multi-channel systems, the measurement result must be
> > related with the corresponding oscilloscope channel. A probe
> > calibration is only valid in combination with the calibrated
> > oscilloscope (indicated in the calibration certificate). The probe
> > calibration must be clearly related to the applied channel."
> > 
> > Regards,
> > Tom
> > 
> > 
> >> From: Schaefer, David [mailto:dschae...@tuvam.com] 
> >> Sent: Monday, July 11, 2016 10:50 PM
> >> To: EMC-PSTC@LISTSERV.IEEE.ORG
> >> Subject: [PSES] Oscilloscope probe calibration
> >> 
> >> All,
> >> 
> >> We're seeing an issue with scope probes, and I'd appreciate suggestions, or
> >> just information on how others handle calibration. I've g

Re: [PSES] Oscilloscope probe calibration

[Douglas Smith]

Hi Rich,
I am familiar with those concepts, but there is apparently quite a bit the 
measurement companies do not understand about their own probes, at least they 
do not publically cover some important issues. The fact they could have added a 
whole octave of usable frequency response for essentially free but did not 
always amazes me. Will cover this Friday.

Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 Email: 
d...@dsmith.org Website: http://dsmith.org
On Tue, Jul 12, 2016 at 10:20, Richard Nute  wrote:




Hi Doug:





In a former life, I worked for a famous scope manufacturer. For a while, I was 
associated with probes.



A passive 10X probe comprises a voltage divider. The nose resistor is 9 
megohms, and the scope input is 1 megohm, yielding a 10 megohm input impedance. 
(Usually, these are precision resistors.) To be a frequency-flat divider, the 
time constant of the probe nose RC must equal the scope input RC. The scope 
input C is about 20 pF. That means probe nose C must be about 2 pF.



Scope input C is not well-controlled. That means the probe nose C or the scope 
input C must be adjusted so that the individual probe RC and the individual 
scope input RC are equal. The probe and scope input channel must be 
“compensated” as a unique system. (Every scope has a square wave port for 
“compensating” the probe to the input channel.)



Probes are made with either adjustable nose C or adjustable base C.



A properly “compensated” probe with a coaxial ground connection to the probe 
tip will meet the accuracy and frequency response claimed by the probe 
manufacturer. At high frequencies, the probe ground lead will reduce the 
accuracy and frequency response.



As has been discussed here, high-frequency response of a probe is highly 
dependent on the probe ground lead. The shorter, the better. Many probes come 
with an assortment of ground leads for different measurements.





Rich





From: Doug Smith [mailto:d...@emcesd.com]
Sent: Monday, July 11, 2016 7:15 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG; Richard Nute 
Subject: Re: [PSES] Oscilloscope probe calibration



Hi Rich,



Although useful, the literature from measurement companies and be misleading 
and rarely descirbe the situation completely. Maybe I should hold a short free 
webinar for anyone interested. I probably have more information on this than 
any other source. If I do the webinar, the limit is 24 computers on the 
connection, first come, first served. Contact me privately if interested, would 
do it later this week in the morning Pacific Time, domestic US or UK only.



Doug


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Re: [PSES] Oscilloscope probe calibration

[Richard Nute]

 

 

Hi Doug:

 

 

In a former life, I worked for a famous scope manufacturer.  For a while, I was 
associated with probes.

 

A passive 10X probe comprises a voltage divider.  The nose resistor is 9 
megohms, and the scope input is 1 megohm, yielding a 10 megohm input impedance. 
 (Usually, these are precision resistors.)  To be a frequency-flat divider, the 
time constant of the probe nose RC must equal the scope input RC.  The scope 
input C is about 20 pF.  That means probe nose C must be about 2 pF.

 

Scope input C is not well-controlled.  That means the probe nose C or the scope 
input C must be adjusted so that the individual probe RC and the individual 
scope input RC are equal.  The probe and scope input channel must be 
“compensated” as a unique system.  (Every scope has a square wave port for 
“compensating” the probe to the input channel.)   

 

Probes are made with either adjustable nose C or adjustable base C.  

 

A properly “compensated” probe with a coaxial ground connection to the probe 
tip will meet the accuracy and frequency response claimed by the probe 
manufacturer.  At high frequencies, the probe ground lead will reduce the 
accuracy and frequency response.  

 

As has been discussed here, high-frequency response of a probe is highly 
dependent on the probe ground lead.  The shorter, the better.  Many probes come 
with an assortment of ground leads for different measurements. 

 

 

Rich

 

 

From: Doug Smith [mailto:d...@emcesd.com] 
Sent: Monday, July 11, 2016 7:15 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG; Richard Nute 
Subject: Re: [PSES] Oscilloscope probe calibration

 

Hi Rich,

 

Although useful, the literature from measurement companies and be misleading 
and rarely descirbe the situation completely. Maybe I should hold a short free 
webinar for anyone interested. I probably have more information on this than 
any other source. If I do the webinar, the limit is 24 computers on the 
connection, first come, first served. Contact me privately if interested, would 
do it later this week in the morning Pacific Time, domestic US or UK only.

 

Doug
   


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discussion list. To post a message to the list, send your e-mail to 


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http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

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Mike Cantwell 

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Jim Bacher:  
David Heald: 

Re: [PSES] Oscilloscope probe calibration

[Douglas Smith]

Here is a bit of suspence for Friday, free webinar on this topic (joining 
details available shortly).the addition of a simple change to the probe 
significantly improves, almost eliminates, frequency response problems due to 
the ground lead and circuit impedance. Can you guess what it is? Got a patent 
on this 30+ ago while at Bell Labs, expired now so in public domain. It applies 
to both active and 10x Hi-z passive probes and is incorporated now in most high 
speed active probes. It can recover an octave of well behaved frequency 
response at essentially no cost.
No spoilers from alumni of my seminars please! Will give the answer next week 
for those that cannot make the free webinar. Just wanted to get people thinking.

Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 Email: 
d...@dsmith.org Website: http://dsmith.org
On Tue, Jul 12, 2016 at 04:17, B Rowland  wrote:
Hello PSES crew;


T Sato wrote:

> "Performance of passive probes strongly depends to the oscilloscope,
> so I think it should always be calibrated with a specific oscilloscope
> channel."

Indeed, not only "should", but MUST, as John Woodgate stressed.

But, as I mentioned, the calibration is often meaningless, if it does not 
account for non-monotonic frequency response, , the Gaussian that is expected, 
which results in unexpected transient response.

Additionally, the calibration becomes "broken" as soon as the probe/scope 
combination is used in any "real world" application where the impedance of the 
DUT circuit is unknown, or not the same as the calibration circuit, since the 
probe reactive loading varies with instantaneous frequency ("typical" 500 MHz 
passive probe reaches 50 Ω loading at about 320 MHz), and the combination of 
probe capacitance, circuit capacitance and ground lead/ground clip/ground 
connection loop size, all cause resonances at rather common frequencies/edge 
rates.

Probably the best 'calibration' is to attach the passive probe to a circuit to 
be tested, and attach a low-capacitance active probe to the same point, to see 
the "real" signal at the passive probe's tip… this could be quite a surprise ;-)

In short, "Your mileage may vary" is good advice when it comes to probing

If Doug Smith does offer a webinar, please do consider attending, if you are at 
all unsure of this whole "can of worms" that probing is!

Best regards,
Barry Rowland
Formerly " Senior Application Specialist, Oscilloscopes", Rohde & Schwarz
(and FAE at Tektronix and Agilent)






On 12/07/2016, at 12:42 PM, "T.Sato"  wrote:

> On Tue, 12 Jul 2016 02:08:04 +0100,
> John Woodgate  wrote:
>
>> Slight under-compensation would cause a brief overshoot to 138 V. In my
>> opinion, probes can't be calibrated except with the scope they are
>> exclusively used with. Covering the cal adjuster with a sticker shows a deep
>> misunderstanding of how passive probes work.
>
> Agreed.
> Performance of passive probes strongly depends to the oscilloscope,
> so I think it should always be calibrated with a specific oscilloscope
> channel.
>
> EURAMET cg-7 (calibration of oscilloscopes),
> https://www.euramet.org/get/?tx_stag_base%5Bfile%5D=3611&tx_stag_base%5Bidentifier%5D=%252Fdocs%252FPublications%252Fcalguides%252FEURAMET_cg-7__v_1.0_Calibration_of_Oscilloscopes.pdf&tx_stag_base%5Baction%5D=downloadRaw&tx_stag_base%5Bcontroller%5D=Base
> also says "For multi-channel systems, the measurement result must be
> related with the corresponding oscilloscope channel. A probe
> calibration is only valid in combination with the calibrated
> oscilloscope (indicated in the calibration certificate). The probe
> calibration must be clearly related to the applied channel."
>
> Regards,
> Tom
>
>
>> From: Schaefer, David [mailto:dschae...@tuvam.com]
>> Sent: Monday, July 11, 2016 10:50 PM
>> To: EMC-PSTC@LISTSERV.IEEE.ORG
>> Subject: [PSES] Oscilloscope probe calibration
>>
>> All,
>>
>> We're seeing an issue with scope probes, and I'd appreciate suggestions, or
>> just information on how others handle calibration. I've got two problems
>> with passive scope probes.
>>
>> First, probe compensation. Compensation depends on the capacitance of the
>> scope being used, so the probe would be adjusted to match that capacitance.
>> Well if the cal house is using a different scope, they'll adjust it to match
>> their capacitance, which may not be what we need. Also, many times the cal
>> sticker then covers the adjustment port, implying the user should not be
>> adjusting that value. I disregard the stickers, but it isn't a good habit to
>> get into.
>>
>> Second, we're seeing variance between in cal probes based on what they're
>> measuring. I had four probes measuring a 1 microsecond rise time transient
>> signal. All were within 5% of the expected peak voltage. Next, all four
>> probes measured a 5 ns rise time transient. Three peak voltages were within
>> 10-15% of the measured 100V(not great, but acceptable). The fourth
>> consistently read aro

Re: [PSES] Electronic versions of standards and DRM - off topic

[Douglas Nix]

Ralph,

Well said! In my experience, very few machine builders ever do software 
verification, and if they do any kind of verification, it’s usually fairly 
superficial. There are large machine builders for whom this is not the case, 
but my practice centres on nano-through-medium sized enterprises, and most of 
those companies just don’t have the resources or the expertise to do a proper 
job of software validation.

Since we can now build anything from the simplest to the most sophisticated 
functions in software relatively easily, it’s not surprising that these are the 
places where safety problems are cropping up. Consider that hardware engineers 
have generally had some guidance over the years in developing safety-related 
systems, but most software engineers, unless their work has specifically taken 
them into the development of safety related software, have never had exposure 
to “safety thinking” in their work. It can be a major paradigm shift.

Doug Nix
d...@mac.com

Success is not the key to happiness. Happiness is the key to success. If you 
love what you are doing, you will be successful. -- Albert Schweitzer



> On 11-Jul-16, at 14:37, Ralph McDiarmid 
>  wrote:
> 
> Ted wrote, "My general advice has been to add a small microcontroller than 
> only handles the safety function so that code for safety was separate, easily 
> testable and didn't need to be touched when the system's main programming was 
> updated."
> 
> That's excellent advice, but something I rarely see done.  The approach has 
> another advantage in that a smaller code size is easier to verify.  As Fred 
> Brooks* once wrote, "Verifications are so much work that only a few 
> substantial programs have every been verified".   We spend months on 
> verifying and regressing testing firmware for our devices, and the program 
> size keeps growing.  I suspect programs tend to expand to fill the available 
> memory space, and our firmware component is now "substantial".  I have often 
> said to my colleagues that we are fast becoming a software company; the 
> hardware is now incidental.   I wouldn't have suggested that 25 years ago.
> 
> 
> * - see IEEE Computer, April 1987,  "No Silver Bullet, Essence and Accidents 
> of Software Engineering"
> 
> 
> Ralph McDiarmid
> Product Compliance
> Engineering
> Solar Business
> Schneider Electric
> 
> 
> -Original Message-
> From: Ted Eckert [mailto:07cf6ebeab9d-dmarc-requ...@ieee.org]
> Sent: Thursday, July 07, 2016 1:56 PM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] Electronic versions of standards and DRM - off topic
> 
> Hello Brian,
> 
> I think that the Technical Program Committee (TPC) has expanded its range of 
> interests for presentations. I'm sorry you had a bad experience with your 
> previous submittals. However, with software and programming becoming a bigger 
> part of safety, there should be new interest in the area. I would hate to see 
> a USB-C power supply switch its output to 20 V, 5 A incorrectly due to a 
> software flaw. There have been changes in the ISPCE focus and the new TPC 
> will probably be more receptive to your submittals. I believe that the 
> current TPC sees the importance of a broader range of topics for the 
> symposium. Please don't let your past experience discourage you.
> 
> I will admit that I have very little experience with software for safety 
> functions. I have only worked for employers where safety was handled by 
> hardware that could not be overridden by software. I have occasionally had 
> engineers ask me about putting a safety function into software. My general 
> advice has been to add a small microcontroller than only handles the safety 
> function so that code for safety was separate, easily testable and didn't 
> need to be touched when the system's main programming was updated. I don't 
> know if that was good advice, but it did result in my engineers deciding it 
> was easier to handle safety in hardware.
> 
> I would be lying if I said I didn't know much about software safety. That 
> would be an overstatement as I know almost nothing about software safety. 
> However, with my employer's reputation, it is probably best for me to stay 
> away from the area. I don't think many engineers would want to buy a car that 
> controlled the antilock brakes with Windows 95. (Feel free to insert your 
> favorite blue screen joke here.)
> 
> http://dilbert.com/strip/2010-08-21
> 
> Ted Eckert
> Microsoft Corporation
> 
> The opinions expressed are my own and do not necessarily reflect those of my 
> employer.
> 
> -Original Message-
> From: Brian O'Connell [mailto:oconne...@tamuracorp.com]
> Sent: Thursday, July 7, 2016 9:31 AM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] Electronic versions of standards and DRM - off topic
> 
> Greetings Mr. Ted of Eckert,
> 
> Have previously commented in this venue, using nauseating and pedantic 
> detail, why the Therac incident is poor example (the root cause was 

Re: [PSES] Oscilloscope probe calibration

[John Woodgate]

I'm surprised they don't want to calibrate primary batteries. (;-)

With best wishes DESIGN IT IN! OOO – Own Opinions Only
www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England

Is there a homeopathic remedy for excessive gullibility?


-Original Message-
From: Cortland Richmond [mailto:k...@earthlink.net] 
Sent: Tuesday, July 12, 2016 2:02 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Oscilloscope probe calibration

On 7/11/2016 9:08 PM, John Woodgate wrote:
> a deep misunderstanding

Metrology department heads should be taken to the lab so they can see when 
their fixed-in-stone calibration is too far off to be used – and shown the 
instructions requiring *user* adjustment of probe compensation.


Cortland Richmond

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Re: [PSES] Oscilloscope probe calibration

[Cortland Richmond]

On 7/11/2016 9:08 PM, John Woodgate wrote:

a deep misunderstanding


Metrology department heads should be taken to the lab so they can see 
when their fixed-in-stone calibration is too far off to be used – and 
shown the instructions requiring *user* adjustment of probe compensation.



Cortland Richmond

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Re: [PSES] Oscilloscope probe calibration

[Cortland Richmond]

On 7/11/2016 5:49 PM, Schaefer, David wrote:


These were all calibrated probes, and three were identical models. The 
one that was way off wasn’t the odd model. Our cal house measures a DC 
voltage for accuracy, and bandwidth.


What’s causing the inaccuracy? How can I prevent this problem in the 
future? Moving to all active probes isn’t an option right now.


In addition to what's been written in other replies, there is a 
difference in calibration if you even hold the oscilloscope probe 
differently when measuring faster, high-frequency signals.  It's always 
better to use the short steel wire (or coaxial tip adapter) ground 
connection provided with a  high-frequency probe when making high-speed, 
high frequency measurements – and changing the ground lead requires 
*readjusting the probe's user calibration*.   That's what the CAL 
terminal on a 'scope front panel is for.


Metrology departments might think probe calibration is sacred and 
forever, but it's not.



Cortland Richmond

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[PSES] Product Compliance Engineer - Electrical - Charles Machine Works (Perry, OK)

[Michael Cantwell]

Posted on behalf of Susan Harmon (sharmon@charlesmachine.works 
). If you’re interested in this position, 
please contact Susan directly. I apologize for the length of the posting, but 
if someone is interested in employment, then I do hope it helps you.

> 
>   
> Product Compliance Engineer - Electrical
> 
> 
> This employee will report to Product Safety and Compliance Manager and assist 
> with all aspects of product safety and compliance for electrical and 
> electronic systems for all Charles Machine Works companies.  This includes 
> serving as the company expert for safety and compliance to all applicable 
> equipment regulations and standards, participating in development of 
> standards, evaluating and providing documents of compliance, and keeping 
> company abreast of changes related to electrical and electronic design and 
> function.  The employee may also perform other duties as assigned.
> 
>  
> ESSENTIAL JOB FUNCTIONS
> 
> Participate in industry meetings to stay abreast of changes to applicable 
> standards and regulations.  This includes safety, electromagnetic 
> compatibility, and emission standards.
> Participate in standards development by reviewing proposed standards, voting 
> on them and leading projects within specific standards organizations.
> Liaise with like personnel from other equipment manufacturers in similar 
> industries.
> Prepare documents of conformity for new electronics products.
> Define and gather test requirements and reports.
> Gain product certification/acceptance for each country.
> Collect necessary agreements and approvals.
> Determine compliance labelling requirements.
> Be familiar with the equipment designed and produced by Charles Machine Works 
> companies.
> Keep appropriate personnel (safety, design, etc…) abreast of any proposed or 
> ratified changes in applicable regulations.
> Assist with development of internal safety procedures/guidelines as related 
> to appropriate standards.
> Understand necessary requirements for wireless frequencies, power levels, and 
> certifications.
> Advise regarding chemical regulations applicable to electrical components.
> Develop and maintain process for functional safety of safety related control 
> systems.
> Assist electrical/electronics design engineers in determining performance 
> levels and testing requirements for compliance.
> Serve as the primary contact for regulatory bodies.
>  
> WORK ENVIRONMENT
> 
> Office most of the time, plant or outdoor environment a small amount of time. 
>  Plant and outdoor conditions include:  temperature and humidity extremes, 
> dirt and noise, and uneven terrain; physical hazards such as construction 
> site hazards, moving machinery, sharp objects, flying debris, and 
> manufacturing equipment; hazardous materials such as gasoline, diesel fuel, 
> solvents, oils, grease, pressurized gases and fluids.
> Occasional evening or weekend work required as needed.
> Occasional overnight travel as needed.
>  
> MINIMUM JOB REQUIREMENTS
> 
> Have a B.S. degree in safety, engineering or related field.
> Be willing to travel up to 25% of the time, including international travel.
> Possess good speaking and writing skills.
> Have good computer skills in Windows, Word, Powerpoint & Excel.
> Have the ability to successfully handle stressful situations and be able to 
> work with individuals with various backgrounds (business, technical, legal, 
> etc...).
>  
> ADDITIONAL DESIRED JOB REQUIREMENTS
> 
> Knowledge of EMC, wireless and safety compliance, regulatory and testing 
> requirements.
> Knowledge of standards: SAE; ISO; ANSI; CEN; and UL.
> 
> 
> Apply to this job now... 
> 
> 


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Re: [PSES] Oscilloscope probe calibration

[B Rowland]

Hello PSES crew;


T Sato wrote:

> "Performance of passive probes strongly depends to the oscilloscope,
> so I think it should always be calibrated with a specific oscilloscope
> channel."

Indeed, not only "should", but MUST, as John Woodgate stressed.

But, as I mentioned, the calibration is often meaningless, if it does not 
account for non-monotonic frequency response, , the Gaussian that is expected, 
which results in unexpected transient response.

Additionally, the calibration becomes "broken" as soon as the probe/scope 
combination is used in any "real world" application where the impedance of the 
DUT circuit is unknown, or not the same as the calibration circuit, since the 
probe reactive loading varies with instantaneous frequency ("typical" 500 MHz 
passive probe reaches 50 Ω loading at about 320 MHz), and the combination of 
probe capacitance, circuit capacitance and ground lead/ground clip/ground 
connection loop size, all cause resonances at rather common frequencies/edge 
rates.

Probably the best 'calibration' is to attach the passive probe to a circuit to 
be tested, and attach a low-capacitance active probe to the same point, to see 
the "real" signal at the passive probe's tip… this could be quite a surprise ;-)

In short, "Your mileage may vary" is good advice when it comes to probing

If Doug Smith does offer a webinar, please do consider attending, if you are at 
all unsure of this whole "can of worms" that probing is!

Best regards,
Barry Rowland
Formerly " Senior Application Specialist, Oscilloscopes", Rohde & Schwarz 
(and FAE at Tektronix and Agilent)






On  12/07/2016, at 12:42 PM, "T.Sato"  wrote:

> On Tue, 12 Jul 2016 02:08:04 +0100,
>  John Woodgate  wrote:
> 
>> Slight under-compensation would cause a brief overshoot to 138 V. In my
>> opinion, probes can't be calibrated except with the scope they are
>> exclusively used with. Covering the cal adjuster with a sticker shows a deep
>> misunderstanding of how passive probes work.
> 
> Agreed.
> Performance of passive probes strongly depends to the oscilloscope,
> so I think it should always be calibrated with a specific oscilloscope
> channel.
> 
> EURAMET cg-7 (calibration of oscilloscopes),
> https://www.euramet.org/get/?tx_stag_base%5Bfile%5D=3611&tx_stag_base%5Bidentifier%5D=%252Fdocs%252FPublications%252Fcalguides%252FEURAMET_cg-7__v_1.0_Calibration_of_Oscilloscopes.pdf&tx_stag_base%5Baction%5D=downloadRaw&tx_stag_base%5Bcontroller%5D=Base
> also says "For multi-channel systems, the measurement result must be
> related with the corresponding oscilloscope channel. A probe
> calibration is only valid in combination with the calibrated
> oscilloscope (indicated in the calibration certificate). The probe
> calibration must be clearly related to the applied channel."
> 
> Regards,
> Tom
> 
> 
>> From: Schaefer, David [mailto:dschae...@tuvam.com] 
>> Sent: Monday, July 11, 2016 10:50 PM
>> To: EMC-PSTC@LISTSERV.IEEE.ORG
>> Subject: [PSES] Oscilloscope probe calibration
>> 
>> All,
>> 
>> We're seeing an issue with scope probes, and I'd appreciate suggestions, or
>> just information on how others handle calibration. I've got two problems
>> with passive scope probes.
>> 
>> First, probe compensation. Compensation depends on the capacitance of the
>> scope being used, so the probe would be adjusted to match that capacitance.
>> Well if the cal house is using a different scope, they'll adjust it to match
>> their capacitance, which may not be what we need. Also, many times the cal
>> sticker then covers the adjustment port, implying the user should not be
>> adjusting that value. I disregard the stickers, but it isn't a good habit to
>> get into. 
>> 
>> Second, we're seeing variance between  in cal probes based on what they're
>> measuring. I had four probes measuring a 1 microsecond rise time transient
>> signal. All were within 5% of the expected peak voltage. Next, all four
>> probes measured a 5 ns rise time transient. Three peak voltages were within
>> 10-15% of the measured 100V(not great, but acceptable). The fourth
>> consistently read around 138 V. Nearly 40% off, just by changing the rise
>> time. 5 ns might be at the edge of the probe's bandwidth, but I'd expect a
>> decrease in level, not an increase. 
>> 
>> These were all calibrated probes, and three were identical models. The one
>> that was way off wasn't the odd model. Our cal house measures a DC voltage
>> for accuracy, and bandwidth. 
>> 
>> What's causing the inaccuracy? How can I prevent this problem in the future?
>> Moving to all active probes isn't an option right now.
>> 
>> Thanks,
>> 
>> David Schaefer
>> 
>> -
>> 
>> This message is from the IEEE Product Safety Engineering Society emc-pstc
>> discussion list. To post a message to the list, send your e-mail to
>> mailto:emc-p...@ieee.org> >
>> All emc-pstc postings are archived and searchable on the web at:
>> http://www.ieee-pses.org/e

Re: [PSES] Using 60 Hz isolation transformer at 400 Hz

[Richard Marshall]

Hi All!

 

A related side-issue to be aware of is the leakage inductance of the
isolating transformer: what is negligible for a 50/60 Hz transformer at
50/60 Hz may not be negligible in 400Hz usage of that same transformer,
particularly if the current waveform is pulsed.

 

Just check the voltage waveform if you suspect anything.

 

As an example of this phenomena even without the factor of transformer
design frequency: last week I needed to explore with an oscilloscope the
function of a tiny 2.5 watt 220V 50Hz power supply embodying a series
capacitor of 0.75 microfarad as a voltage-dropper.  This should have drawn
6mS rectangular current pulses from the ac mains.  For my safety I used the
only available isolating transformer; a 50Hz 300watt isolating transformer.
This had the effect that current pulse tops exhibited considerable "ringing"
because of the transformer leakage inductance resonating with the series
capacitor in the power supply.

 

Not often  a problem, but just remember the possibility.

 

Richard

 

Richard Marshall Laboratories,

30 Ox Lane, Harpenden, Herts.,AL5 4HE, UK 

+44 (0)1582 460815   www.design-emc.co.uk

Member of the EMC Industry Association

 

 

Richard

 

Richard Marshall Laboratories,

30 Ox Lane, Harpenden, Herts.,AL5 4HE, UK 

+44 (0)1582 460815   www.design-emc.co.uk

Member of the EMC Industry Association

 

From: David Gelfand [mailto:david.gelf...@kontron.com] 
Sent: 08 July 2016 17:25
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Using 60 Hz isolation transformer at 400 Hz

 

Esteemed colleagues,

 

I have to prepare a debug setup for a DO-160 test, and we need to float the
400 Hz power supply.  Can we use an isolation transformer rated at 60Hz, 150
VA?  The EUT draws about 10W.  Your input is most appreciated.

 

Regards,

 

David

 

 

 

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Re: [PSES] Oscilloscope probe calibration

[T.Sato]

On Tue, 12 Jul 2016 02:08:04 +0100,
  John Woodgate  wrote:

> Slight under-compensation would cause a brief overshoot to 138 V. In my
> opinion, probes can't be calibrated except with the scope they are
> exclusively used with. Covering the cal adjuster with a sticker shows a deep
> misunderstanding of how passive probes work.

Agreed.
Performance of passive probes strongly depends to the oscilloscope,
so I think it should always be calibrated with a specific oscilloscope
channel.

EURAMET cg-7 (calibration of oscilloscopes),
https://www.euramet.org/get/?tx_stag_base%5Bfile%5D=3611&tx_stag_base%5Bidentifier%5D=%252Fdocs%252FPublications%252Fcalguides%252FEURAMET_cg-7__v_1.0_Calibration_of_Oscilloscopes.pdf&tx_stag_base%5Baction%5D=downloadRaw&tx_stag_base%5Bcontroller%5D=Base
also says "For multi-channel systems, the measurement result must be
related with the corresponding oscilloscope channel. A probe
calibration is only valid in combination with the calibrated
oscilloscope (indicated in the calibration certificate). The probe
calibration must be clearly related to the applied channel."

Regards,
Tom


> From: Schaefer, David [mailto:dschae...@tuvam.com] 
> Sent: Monday, July 11, 2016 10:50 PM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: [PSES] Oscilloscope probe calibration
>  
> All,
>  
> We're seeing an issue with scope probes, and I'd appreciate suggestions, or
> just information on how others handle calibration. I've got two problems
> with passive scope probes.
>  
> First, probe compensation. Compensation depends on the capacitance of the
> scope being used, so the probe would be adjusted to match that capacitance.
> Well if the cal house is using a different scope, they'll adjust it to match
> their capacitance, which may not be what we need. Also, many times the cal
> sticker then covers the adjustment port, implying the user should not be
> adjusting that value. I disregard the stickers, but it isn't a good habit to
> get into. 
>  
> Second, we're seeing variance between  in cal probes based on what they're
> measuring. I had four probes measuring a 1 microsecond rise time transient
> signal. All were within 5% of the expected peak voltage. Next, all four
> probes measured a 5 ns rise time transient. Three peak voltages were within
> 10-15% of the measured 100V(not great, but acceptable). The fourth
> consistently read around 138 V. Nearly 40% off, just by changing the rise
> time. 5 ns might be at the edge of the probe's bandwidth, but I'd expect a
> decrease in level, not an increase. 
>  
> These were all calibrated probes, and three were identical models. The one
> that was way off wasn't the odd model. Our cal house measures a DC voltage
> for accuracy, and bandwidth. 
>  
> What's causing the inaccuracy? How can I prevent this problem in the future?
> Moving to all active probes isn't an option right now.
>  
> Thanks,
>  
> David Schaefer
>  
> -
> 
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to
> mailto:emc-p...@ieee.org> >
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
> Website: http://www.ieee-pses.org/
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> unsubscribe)  
> List rules: http://www.ieee-pses.org/listrules.html 
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> 
> -
> 
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> 
> 
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