Re robust designs. There is also a powerful inertia effect. If you make a new probe that gives different results, what happens about 'pass' decisions made using the old probes? You wouldn't want to make problems for the customers, would you? Many of the outline testing networks in CISPR 16-1 are 'hands-off' because of this, even though some are very vintage indeed.

John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2018-03-07 14:52, Patrick wrote:
Hello Ed -
Great story- thanks for sharing!

Just last year, we had a broken sensor head on a HI-6053.
It was built circa 2015, so it would be considered a "modern" probe.
I did the same as you and took it apart - it was already broken, so nothing to lose!
(how many of us have been doing that since we were kids!)

The description you give of the "old" probe matches exactly what I found inside the HI6053.
Dimensions were a bit different, and electronics are in a square box.
But the basic design of sensor and high impedance connecting cables are the same!
I guess some designs are robust enough to survive for decades.

Thanks again for the story.

BTW- thanks also for yesterday's story about the evolution of our industry. It reminds me that what we think is "settled" is really just the boundary of our understanding.
And, as our understanding grows then those boundaries move too.

Always great to hear your perspective!
Thank you !

On Tue, Mar 6, 2018 at 2:57 PM, Edward Price <e...@jwjelp.com <mailto:e...@jwjelp.com>> wrote:

    *Patrick:*

    **

    *The probe manufacturer says something like “keep the probe box
    away or out of the field” or “best results are obtained with the
    probe placed on a slant.” But then they show us isotropicity data
    that promises +/- ¼ dB. It seems like those are contradictory
    statements.*

    *Back around 2002, I decided to dissect a dead Narda 8762(?) probe
    which a customer helped me drop. The Narda was a white Fiberglas,
    300 MHz to 1 GHz probe that looked like a very elegant German
    “potato masher” hand grenade equipped with a cable that plugged
    into an IFI EFS field sensor. I wish I had taken some good
    pictures of the project, as few people venture that deep into such
    expensive territory.*

    *The head contained the orthogonal three-dipole array, with the
    conductive arms looking like gold foil on a thin Fiberglass
    substrate. The length of each dipole was about 1.5 inches. The
    sensing elements might have been thermocouples, thermistors or
    diodes, and they were mounted in the dipoles. Each sensor was also
    connected to a pair of very high resistance plastic wires
    (possibly doped with carbon like automotive spark plug wires) that
    ran to the far end of the stalk where an analog signal
    conditioning amplifier summed the three channels and provided a DC
    output proportional to field strength. I was struck by the
    delicacy of the sensor head, looking at what must have been a very
    labor intensive assembly.*

    *BTW, the signal conditioning amplifier was enclosed in a ¾”
    diameter by 4” long section of tubular steel, so it was obvious
    that this conductive mass (not to mention the shielded,
    multi-conductor power & signal cable) would distort the measured
    field and degrade the isotropicity.*

    **

    */Ed Price
    /**WB6WSN**/
    /**Chula Vista, CA USA**//*

    **

    *From:*Patrick [mailto:conwa...@gmail.com
    <mailto:conwa...@gmail.com>]
    *Sent:* Tuesday, March 06, 2018 7:37 AM
    *To:* Edward Price
    *Subject:* Re: [PSES] Field probe calibration

    Hello Ed -

      Good morning!

      You are correct - the factors stored in the probe correct for
    the non-linearities of the diode detector.

          (  as a side note- hearing a presentation live, and
    asking/answering questions, is always more educational than a
    sterile slide deck.

          i wish we all could sit through this presentation, ask
    questions, and have dialog. )

    Did you notice the warnings about errors possible in the
    calibration process?

    For instance, the "probe on a stick" is calibrated at an angle???

    And for that probe they say the electronics box should be kept out
    of the field???

       I understand the reasons, but keeping the box out of the field
    is nearly impossible for most of our semi-anechoic chamber
    applications!!

       And I rarely see them used at the same angle as calibrated.

      How does one quantify those effects?

      (...a topic for another thread ?)

    But, getting back to the frequency response question...

    Here is what I recall-

    ... As shown in the slides, the detector is connected across a
    small (tiny?) dipole.

         the size of the dipole has some real-world limits.

         large enough to capture enough power to make a measurement
    possible.

         small enough to minimize disturbance in the field.

         the three orthogonal dipoles have to be close enough to
    represent the same physical space.

         So the size, placement and response is a compromise away from
    "ideal" (i.e. not flat ).

    ... IMHO, there is nothing revolutionary in that information.

        But, maybe I missed something?

        Let me know your thoughts.

    I would encourage local chapters to contact ETS, and ask them if
    they could present at the local chapter meeting.

    (DISCLAIMER - I have no affiliation with ETS, I just like the idea
    of learning something new about something that was thought to be
    settled...)

    -

    ----------------------------------------------------------------

    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 &LT;emc-p...@ieee.org <mailto:emc-p...@ieee.org>&GT;

    All emc-pstc postings are archived and searchable on the web at:
    http://www.ieee-pses.org/emc-pstc.html
    <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/
    <http://product-compliance.oc.ieee.org/> can be used for graphics
    (in well-used formats), large files, etc.

    Website: http://www.ieee-pses.org/
    Instructions: http://www.ieee-pses.org/list.html (including how to
    unsubscribe) <http://www.ieee-pses.org/list.html>
    List rules: http://www.ieee-pses.org/listrules.html
    <http://www.ieee-pses.org/listrules.html>

    For help, send mail to the list administrators:
    Scott Douglas &LT;sdoug...@ieee.org <mailto:sdoug...@ieee.org>&GT;
    Mike Cantwell &LT;mcantw...@ieee.org <mailto:mcantw...@ieee.org>&GT;

    For policy questions, send mail to:
    Jim Bacher &LT;j.bac...@ieee.org <mailto:j.bac...@ieee.org>&GT;
    David Heald &LT;dhe...@gmail.com <mailto:dhe...@gmail.com>&GT;




--
//
Patrick
-
----------------------------------------------------------------

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 <emc-p...@ieee.org <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/
Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas <sdoug...@ieee.org <mailto:sdoug...@ieee.org>>
Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org>>

For policy questions, send mail to:
Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org>>
David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com>>



-
----------------------------------------------------------------
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 <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/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas <sdoug...@ieee.org>
Mike Cantwell <mcantw...@ieee.org>

For policy questions, send mail to:
Jim Bacher:  <j.bac...@ieee.org>
David Heald: <dhe...@gmail.com>

Reply via email to