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> 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] > *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 < > 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) <http://www.ieee-pses.org/list.html> > 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> > -- // 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> 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>
