PORTABLE PROTON MAGNETOMETER teardown, and tech info wanted

[oz2cpu]

Looks like really old design 73 is written on many components
and since the displays are bulb / filament segments, i think 1973 is the year for the main parts.

If you know more about the use, or features of this unit, please post comments,
the values i measured match the lines of the map picture.

what type of people will need such an instrument ?
the values measured is for ground survey usage ?
or ground material investigations ?

i put a link to the datasheet in the video description
since it is NOT allowed to copy and use, anything from the manual

https://youtu.be/FdRYquOaywE

[Kleinstein]

This looks like a keind earths field NMR.  The sensor should contain a rather heavy copper coil and some liquid (water or maybe some parafine / oil) with a high hydrogen contend. One mode of operation is to send a short (e.g. 100 ms ?) pulse of rather high current (and thus the large number of quite powerful batteries) to the coil and than turn it of fast and observe the ringing after that.
The NMR signal frequency should not depend on the orientation, but only on the field strength. However the orientation can effect the signal strength. So the north orientation should be for this reason. The neasured field should reflect the reequency with the right (depends slightly on the chemistry of the probe material), but otherwise just natural constants. So this can make a very stable and quite high resolution magnetometer.

To get the strongest signal, the coil is tuned with a capacitor to get in resonance.

I am somehow missing an indication if the sensor really captures an MR signal, or only the LC resonant decay.  I tuned way off, expect to seen on the LC resonance and thus a number corresponding the the setting of the switch. Chances are the 2 single lamps may show an idication there.

I don't thing that instrument is of any practical use anymore, so more like a collectors item. Modern versions could probably do a lot better, with more resolution, data collection (e.g. trend charts) and automatic tuning, though the sensor part may not have changed much.

[Gyro]

It puts me in mind of an old Proton Magnetometer project in Practical Electronics magazine, back in October 1970. It was fairly primitive in using relays for coil energise / sense switching, but used two heads (bottles) in differential mode which would have improved sensitivity / selectivity.

I'm not sure how relevant it is from the electronics perspective, but it should certainly help you with the basic principles...  https://worldradiohistory.com/UK/Practical-Electronics/70s/Practical-Electronics-1970-10.pdf

[oz2cpu]

the sensor is a coil of some sort, and it is full with filtered GASOLINE !
i did not open the sensor for investigations, since this will ruin in,
i was very close to, just for the research, but i try not to brake stuff that could make someone else happy.

since my space for old funny stuff is limited, i put in for sale where most collectors of special electronics will find it,
and bingo 12hrs later, someone else is now the owner of this unit.

I got a few other odd things comming up soon, so stay tuned, look at my youtube list "teardown"

[SeanB]

Hopefully that Fluke calibrator goes to a good home.....

[RoGeorge]

It puts me in mind of an old Proton Magnetometer project in Practical Electronics magazine, back in October 1970.
...
https://worldradiohistory.com/UK/Practical-Electronics/70s/Practical-Electronics-1970-10.pdf

Thanks!  I didn't know a metal detector can also be made based on NMR.
Now I want to try that, too, one day! 

i put a link to the datasheet in the video description
since it is NOT allowed to copy and use, anything from the manual

https://youtu.be/FdRYquOaywE

I see no datasheet link in the video description.   

[Kleinstein]

The NMR detector would also react to metal, but I would not consider this the normal use.

The main advantage of a NMR based magenetometer is that one gets a very stable, near primary reference grade sensitivity. The output signal is a frequency that is only set by the magentic field and to small part the material the hydrogen is in. It is a bit noisy, but the resolution can be quite good, as a high resolution frequency measurement is relatively easy.

There are some DIY plans around that use a soundcard and PC to do most of the signal processing. This fits well for a signal in the 1 kHz range for the "normal" earths field. Digital signal processing can really help as it is a decaying pulse and not an easy constant tone to measure.

[Haenk]

I'm not sure how relevant it is from the electronics perspective, but it should certainly help you with the basic principles...  https://worldradiohistory.com/UK/Practical-Electronics/70s/Practical-Electronics-1970-10.pdf

On a completely irrelevant sidenote, there is a "Sinclair" branded amplifier IC onpage 757. Is that just some rebranded IC (Toshiba?)?