If you had one what would you use it for
in [Design]
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From: brent on 21 Oct 2009 21:04 On Oct 21, 8:38 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- Web-Site.com> wrote: > On Wed, 21 Oct 2009 17:35:15 -0700 (PDT), brent > > > > > > <buleg...(a)columbus.rr.com> wrote: > >On Oct 21, 8:05 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- > >Web-Site.com> wrote: > >> On Wed, 21 Oct 2009 16:58:33 -0700 (PDT), brent > > >> <buleg...(a)columbus.rr.com> wrote: > >> >On Oct 21, 10:51 am, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- > >> >Web-Site.com> wrote: > >> >> On Wed, 21 Oct 2009 07:37:36 -0700, John Larkin > > >> >> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> >On Wed, 21 Oct 2009 06:21:02 -0700 (PDT), MooseFET > >> >> ><kensm...(a)rahul.net> wrote: > > >> >> >>Imagine you had a sensor that could measure very small magnetic > >> >> >>fields. It measures with a noise floor of about 0.1fT. Unfortunately > >> >> >>the band width is only a few hundred Hz and it only works inside a > >> >> >>shield. > > >> >> >>What would you use such a sensor for? The best I've thought of is > >> >> >>detecting the flow of current in a PCB to find a short circuit. > > >> >> >You need high spatial resolution for a general-purpose board short > >> >> >finder. Magnetically, you can do it with a pulsed current source and a > >> >> >really tiny ferrite-core pickup coil. I do it lately with a DC source > >> >> >and a thermal imager, so you can *see* the current path. > > >> >> >John > > >> >> A microvolt meter makes short finding trivial. Somewhere back in time > >> >> I posted how I made my own at GenRad in the late '70's > > >> >> ...Jim Thompson > >> >> -- > >> >> | James E.Thompson, CTO | mens | > >> >> | Analog Innovations, Inc. | et | > >> >> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > >> >> | Phoenix, Arizona 85048 Skype: Contacts Only | | > >> >> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > >> >> | E-mail Icon athttp://www.analog-innovations.com| 1962 | > > >> >> Cranky Old Git With Engineering Mind Faster Than a Speeding Prissy > > >> >Did you woek at gen rad? > > >> >I got some questions about someone I knew that worked there in that > >> >time frame > > >> I was Analog Guru at GenRad Portable Products Division, Phoenix, from > >> 1977 to 1987. > > >> ...Jim Thompson > [snip] > > >My friend worked out of Boston. I think he must have left around 1977 > >or so (it would have been shortly before going public). He said that > >he worked there for many years prior to Gen rad going public, and they > >paid many of their engineers in shares of the company. He was one of > >the engineers with quite a lot of this stock. There was a stipulation > >that the stock must be sold back to the company if the employee left > >the company. Just prior to the company going public, they essentially > >fired several of these high engineer holders of company stock and > >forced them to sell at the agreed upon rate back to the company. Some > >short time later, the company went public and those shares that he had > >to sell back would have been worth 250K (that is number I think he > >said it cost him in 1970 something dollars) > > >Have you heard this story? > > I don't know when they went public. I do know that I lost $40K > overnight in the infamous 1984 debacle :-( > > ...Jim Thompson > -- > | James E.Thompson, CTO | mens | > | Analog Innovations, Inc. | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | Phoenix, Arizona 85048 Skype: Contacts Only | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon athttp://www.analog-innovations.com| 1962 | > > Cranky Old Git With Engineering Mind Faster Than a Speeding Prissy I was working with this guy at Raytheon in 1984. So he did not experience that debacle. It was good fun working with him. He was at the vert tail end of his career, and I was at the beginning of mine. Most of my peers were doing digital and computer stuff. I was doing Rf and the big cell boom had not taken place so I was working with all these old guys. Several had worked on radar duing WWII. They worked at the radar lab at(I think) MIT. It was quite fun, I would work for 4 hours, listen to war stories for 4 hours and then go home at night and study for four hours to actually learn the stuff I was already supposed to know but did not feel I had learned very well in college.
From: Jim Thompson on 21 Oct 2009 21:15 On Wed, 21 Oct 2009 18:04:39 -0700 (PDT), brent <bulegoge(a)columbus.rr.com> wrote: >On Oct 21, 8:38�pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- >Web-Site.com> wrote: >> On Wed, 21 Oct 2009 17:35:15 -0700 (PDT), brent >> >> >> >> >> >> <buleg...(a)columbus.rr.com> wrote: >> >On Oct 21, 8:05�pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- >> >Web-Site.com> wrote: >> >> On Wed, 21 Oct 2009 16:58:33 -0700 (PDT), brent >> >> >> <buleg...(a)columbus.rr.com> wrote: >> >> >On Oct 21, 10:51�am, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- >> >> >Web-Site.com> wrote: >> >> >> On Wed, 21 Oct 2009 07:37:36 -0700, John Larkin >> >> >> >> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> >On Wed, 21 Oct 2009 06:21:02 -0700 (PDT), MooseFET >> >> >> ><kensm...(a)rahul.net> wrote: >> >> >> >> >>Imagine you had a sensor that could measure very small magnetic >> >> >> >>fields. �It measures with a noise floor of about 0.1fT. �Unfortunately >> >> >> >>the band width is only a few hundred Hz and it only works inside a >> >> >> >>shield. >> >> >> >> >>What would you use such a sensor for? �The best I've thought of is >> >> >> >>detecting the flow of current in a PCB to find a short circuit. >> >> >> >> >You need high spatial resolution for a general-purpose board short >> >> >> >finder. Magnetically, you can do it with a pulsed current source and a >> >> >> >really tiny ferrite-core pickup coil. I do it lately with a DC source >> >> >> >and a thermal imager, so you can *see* the current path. >> >> >> >> >John >> >> >> >> A microvolt meter makes short finding trivial. �Somewhere back in time >> >> >> I posted how I made my own at GenRad in the late '70's >> >> >> >> � � � � � � � � � � � � � � � � � � � � ...Jim Thompson >> >> >> -- >> >> >> | James E.Thompson, CTO � � � � � � � � � � � � � �| � �mens � � | >> >> >> | Analog Innovations, Inc. � � � � � � � � � � � � | � � et � � �| >> >> >> | Analog/Mixed-Signal ASIC's and Discrete Systems �| � �manus � �| >> >> >> | Phoenix, Arizona �85048 � �Skype: Contacts Only �| � � � � � � | >> >> >> | Voice:(480)460-2350 �Fax: Available upon request | �Brass Rat �| >> >> >> | E-mail Icon athttp://www.analog-innovations.com|� �1962 � � | >> >> >> >> Cranky Old Git With Engineering Mind Faster Than a Speeding Prissy >> >> >> >Did you woek at gen rad? >> >> >> >I got some questions about someone I knew that worked there in that >> >> >time frame >> >> >> I was Analog Guru at GenRad Portable Products Division, Phoenix, from >> >> 1977 to 1987. >> >> >> � � � � � � � � � � � � � � � � � � � � ...Jim Thompson >> [snip] >> >> >My friend worked out of Boston. �I think he must have left around 1977 >> >or so (it would have been shortly before going public). �He said that >> >he worked there for many years prior to Gen rad going public, and they >> >paid many of their engineers in shares of the company. �He was one of >> >the engineers with quite a lot of this stock. �There was a stipulation >> >that the stock must be sold back to the company if the employee left >> >the company. �Just prior to the company going public, they essentially >> >fired several of these high engineer holders of company stock and >> >forced them to sell at the agreed upon rate back to the company. �Some >> >short time later, the company went public and those shares that he had >> >to sell back would have been worth 250K (that is number I think he >> >said it cost him in 1970 something dollars) >> >> >Have you heard this story? >> >> I don't know when they went public. �I do know that I lost $40K >> overnight in the infamous 1984 debacle :-( >> >> � � � � � � � � � � � � � � � � � � � � ...Jim Thompson >> -- >> | James E.Thompson, CTO � � � � � � � � � � � � � �| � �mens � � | >> | Analog Innovations, Inc. � � � � � � � � � � � � | � � et � � �| >> | Analog/Mixed-Signal ASIC's and Discrete Systems �| � �manus � �| >> | Phoenix, Arizona �85048 � �Skype: Contacts Only �| � � � � � � | >> | Voice:(480)460-2350 �Fax: Available upon request | �Brass Rat �| >> | E-mail Icon athttp://www.analog-innovations.com| � �1962 � � | >> >> Cranky Old Git With Engineering Mind Faster Than a Speeding Prissy > >I was working with this guy at Raytheon in 1984. So he did not >experience that debacle. > >It was good fun working with him. He was at the vert tail end of his >career, and I was at the beginning of mine. Most of my peers were >doing digital and computer stuff. I was doing Rf and the big cell >boom had not taken place so I was working with all these old guys. >Several had worked on radar duing WWII. They worked at the radar lab >at(I think) MIT. > >It was quite fun, I would work for 4 hours, listen to war stories for >4 hours and then go home at night and study for four hours to actually >learn the stuff I was already supposed to know but did not feel I had >learned very well in college. Sounds like when I was young... work all day, then go home, eat dinner with wife and kids, then doodle electronic ideas all evening, all the way thru Jack Paar ;-) BTW: I covered all my expenses, beyond the basics provided by my MIT Alumni Fund National Scholarship, by working as a technician at MIT's Building 20 ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Cranky Old Git With Engineering Mind Faster Than a Speeding Prissy
From: MooseFET on 21 Oct 2009 21:44 On Oct 21, 7:24 am, Spehro Pefhany <speffS...(a)interlogDOTyou.knowwhat> wrote: > On Wed, 21 Oct 2009 06:21:02 -0700 (PDT), MooseFET > > <kensm...(a)rahul.net> wrote: > > >Imagine you had a sensor that could measure very small magnetic > >fields. It measures with a noise floor of about 0.1fT. > > Per root Hz? Yes 0.1fT per root Hz at about 100Hz. Carefully avoiding trying to measure it at a multiple of the mains etc. > > Unfortunately > >the band width is only a few hundred Hz and it only works inside a > >shield. > >What would you use such a sensor for? The best I've thought of is > >detecting the flow of current in a PCB to find a short circuit. > > Nano (or maybe pico) voltmeter. Did you perhaps mean pico amp? > > What are you talking about? A SERF magnetometer? Bingo! we can't talk details here.
From: MooseFET on 21 Oct 2009 21:46 On Oct 21, 7:37 am, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Wed, 21 Oct 2009 06:21:02 -0700 (PDT), MooseFET > > <kensm...(a)rahul.net> wrote: > > >Imagine you had a sensor that could measure very small magnetic > >fields. It measures with a noise floor of about 0.1fT. Unfortunately > >the band width is only a few hundred Hz and it only works inside a > >shield. > > >What would you use such a sensor for? The best I've thought of is > >detecting the flow of current in a PCB to find a short circuit. > > You need high spatial resolution for a general-purpose board short > finder. Magnetically, you can do it with a pulsed current source and a > really tiny ferrite-core pickup coil. I do it lately with a DC source > and a thermal imager, so you can *see* the current path. The measurement volume is only a few mm across so it may work for the job but yes thermal or just a DVM tracking the drop in the trace is simpler. > > John
From: MooseFET on 21 Oct 2009 21:48
On Oct 21, 8:15 am, Jan Panteltje <pNaonStpealm...(a)yahoo.com> wrote: > On a sunny day (Wed, 21 Oct 2009 06:21:02 -0700 (PDT)) it happened MooseFET > <kensm...(a)rahul.net> wrote in > <b2da0b94-f086-42e1-bf3a-28bb10499...(a)x6g2000prc.googlegroups.com>: > > > > >Imagine you had a sensor that could measure very small magnetic > >fields. It measures with a noise floor of about 0.1fT. Unfortunately > >the band width is only a few hundred Hz and it only works inside a > >shield. > > >What would you use such a sensor for? The best I've thought of is > >detecting the flow of current in a PCB to find a short circuit. > > Brain current imaging? Not a bad idea. The person would have to hold still in a very well shielded room but it would be less bothersome than an MRI. |