UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Other Discussions > Homebrew Equipment

Notices

Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members.

Closed Thread
 
Thread Tools
Old 30th May 2017, 8:50 pm   #1
Ian - G4JQT
Octode
 
Ian - G4JQT's Avatar
 
Join Date: Jun 2004
Location: Reading/Fakenham, UK.
Posts: 1,320
Default Magnetometer.

I've got this vintage germanium PNP transistor circuit which claims to be a magnetometer.

No idea how sensitive it would be, but more to the point is it likely to work at all? I know there are more modern designs, but thought this one looked like nostalgic fun to reproduce as I have all the parts apart from the coil - which I'll have to improvise.

As far as I can see it's a conventional audio amp up to Q3, and I'm guessing D1 sets the bias on Q4, Q5 although I'm not sure the latching circuit would work. I guess a diode across the relay would be s sensible addition too.

Not sure where I'll get that 10k pick-up coil!

Any thoughts?

Thanks,

Ian
Attached Thumbnails
Click image for larger version

Name:	magfsr.jpg
Views:	250
Size:	35.8 KB
ID:	143610  
Ian - G4JQT is offline  
Old 31st May 2017, 10:53 am   #2
G8HQP Dave
Rest in Peace
 
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
Default Re: Magnetometer.

It will detect an AC magnetic field. If you wave it around fast enough it might even detect a constant field. No idea how sensitive, but I suspect not too good. It is essentially an audio amp feeding a relay, with a latch to hold on a buzzer when the threshold has been reached.
G8HQP Dave is offline  
Old 31st May 2017, 7:41 pm   #3
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,190
Default Re: Magnetometer.

There was an interesting project in Practical Electronics in the early 1970s entitled 'Proton Spin Magnetometer'. Apperently it detected small changes in magnetic fields by flipping the spins on the hydrogen nuclei in water. IIRC it was all discrete transistors and didn't look that complicated.
TonyDuell is offline  
Old 31st May 2017, 8:26 pm   #4
G8HQP Dave
Rest in Peace
 
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
Default Re: Magnetometer.

I remember the picture of a wooden beam with a plastic bottle at each end.
G8HQP Dave is offline  
Old 31st May 2017, 8:35 pm   #5
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Magnetometer.

https://archive.org/stream/Practical...e/n31/mode/2up

Lawrence.
ms660 is offline  
Old 1st Jun 2017, 9:18 am   #6
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Magnetometer.

Quote:
Originally Posted by TonyDuell View Post
There was an interesting project in Practical Electronics in the early 1970s entitled 'Proton Spin Magnetometer'.
Hi.

Yes, the project was in the October 1970 issue and I built this magnetometer about 13 years ago but didn't get around to winding the two detector coils which are mounted on the boom which is carried. I would like to try and complete this as it's one of many unfinished projects. I'll have to locate the magnetometer and take a few pics.

Regards
Symon.

EDIT: Just noticed Lawrence's link to the article

Last edited by Philips210; 1st Jun 2017 at 9:20 am. Reason: Additional text
Philips210 is offline  
Old 1st Jun 2017, 10:01 am   #7
Wendymott
Octode
 
Wendymott's Avatar
 
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,782
Default Re: Magnetometer.

In the 70's I worked in the Electronics workshop of the Physics dept at Bradford Uni. Our main interest was Geo Physical Surveying. This involved developing instruments to survey archaeological sites. Various instruments were developed, including the Earth Resistivity meter, Flux gate Magnetometer, Proton Magnetometer and the Induction loop Instrument.
The item mentioned above, was an Induction loop detector, which although portable is probably the worst instrument for serious survey work. The other two types, Resistivity and Magnetometers are for different types of survey.
Resitivity, measures as you would expect the resistance of the soil under two probes, with another two probes sited well away from the survey area. It is in effect a wheatstone bridge, with one current probe and one voltage probe, in each area. The current was 1 Khz at 5 m/A a constant current generator. The voltage was measured with a syncro rectifier, and we could measure resistance up to 1K, down to 10R FSD .
The magnetometers were designed to measure magnetic differences, such as in Burnt hearths , metal working areas, pottery kilns etc.
The induction loop instrument, was developed as a differential loop instrument to vastly increase its sensitivity, and with phase detectors, could identify, ferrous / non ferrous, metals, and non metalic.
However to balance the null, was very difficult, and was abandoned in favour of fluxgate and proton magnetometers
All these instruments were developed to a high degree of sophistication "for the time".
However with the much improved semiconductors of today, these instruments are now very sophisticated.
__________________
Should get out more.

Regards
Wendy G8BZY
Wendymott is offline  
Old 1st Jun 2017, 11:26 am   #8
Ian - G4JQT
Octode
 
Ian - G4JQT's Avatar
 
Join Date: Jun 2004
Location: Reading/Fakenham, UK.
Posts: 1,320
Default Re: Magnetometer.

Excellent posts everyone. Thanks for the input and links.

Ian
Ian - G4JQT is offline  
Old 2nd Jun 2017, 10:11 am   #9
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Magnetometer.

Hi.

A few pics of my Proton Magnetometer built using 0.15" matrix board yet to be completed.

Regards
Symon
Attached Thumbnails
Click image for larger version

Name:	PM1.jpg
Views:	116
Size:	25.5 KB
ID:	143758   Click image for larger version

Name:	PM2.jpg
Views:	108
Size:	48.3 KB
ID:	143759   Click image for larger version

Name:	PM3.jpg
Views:	110
Size:	128.0 KB
ID:	143760   Click image for larger version

Name:	PM4.jpg
Views:	104
Size:	130.9 KB
ID:	143761   Click image for larger version

Name:	PM5.jpg
Views:	122
Size:	134.5 KB
ID:	143762  

Philips210 is offline  
Old 2nd Jun 2017, 10:13 am   #10
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Magnetometer.

A couple more pics of the magnetometer.

Symon
Attached Thumbnails
Click image for larger version

Name:	PM6.jpg
Views:	85
Size:	81.4 KB
ID:	143763   Click image for larger version

Name:	PM7.jpg
Views:	82
Size:	59.9 KB
ID:	143764  
Philips210 is offline  
Old 2nd Jun 2017, 11:49 am   #11
JacKam_
Pentode
 
JacKam_'s Avatar
 
Join Date: Jul 2015
Location: Newbury, Berkshire, UK.
Posts: 243
Default Re: Magnetometer.

Simon, your project looks interesting, What kind of coils you need ?

I also have a long list of unfinished projects, for example a cosmic ray detector. A year ago I bought a lot of GM tubes, planning to stack them in 4 layers, than make a display looking like 4d led cube.

I wish we had a new discussion chapter like "My projects 'on hold'", about what we are planning, but can not start for different reasons...

Thank you,

Jacek.
JacKam_ is offline  
Old 2nd Jun 2017, 12:38 pm   #12
mole42uk
Nonode
 
mole42uk's Avatar
 
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
Default Re: Magnetometer.

Quote:
Originally Posted by JacKam_ View Post
I wish we had a new discussion chapter like "My projects 'on hold'", about what we are planning, but can not start for different reasons...
I'd like to have such a thread, but in my case it'd be filled with projects I started but haven't finished.....
__________________
Richard

Index:
recursive loop: see recursive loop
mole42uk is online now  
Old 2nd Jun 2017, 9:06 pm   #13
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Magnetometer.

Quote:
Originally Posted by JacKam_ View Post
Simon, your project looks interesting, What kind of coils you need ?
Hi Jacek

The detector coils each comprise 750 turns of 24 s.w.g. enamelled copper wire wound on a plastic pill container.
This is filled with distilled water. Details of these coils can be seen in the article that Lawrence provided the link for in post #5. Part of the reason for not completing the project was due to not being able to locate suitable pill containers. It shouldn't be difficult to use a modern size container and make slight alterations to the number of turns to achieve a similar inductance, typically 21mH.
The original Mullard Vinkor pot cores used in the main amplifier and the meter amplifier were obviously not available when I built the project. I used the RM series with adjuster and made slight modifications to the windings. I'll have to locate my notes to check on this.
It was a very interesting project to build and I would like to get it completed. Practical Electronics had some good ideas and novel projects back then and I'm sure many of their circuits are still worth building even now.

Regards
Symon.
Philips210 is offline  
Old 3rd Jun 2017, 3:22 pm   #14
Wendymott
Octode
 
Wendymott's Avatar
 
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,782
Default Re: Magnetometer.

Symon. Nice one.... Our development in 1973, lead to using Phase locked loops to detect the minute signals from the coils, as my attempts at building narrow tuned amps was abysmal. Each output was then squared and processed digitally...... Oh for micro controllers then.........
One of our colleagues.... went on to form Geoscan Technologies, whom supplies the world of archaeology and other agencies with the above types of survey equipment.
Happy experimenting.
__________________
Should get out more.

Regards
Wendy G8BZY

Last edited by Wendymott; 3rd Jun 2017 at 3:23 pm. Reason: Typo
Wendymott is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 7:03 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.