Geometrics G-856 Gradiometer Option

[Magbird]

Hi all,

I have a G-856 with a spare sensor and I would like to make a gradiometer from it. Geometrics offers a Gradiometer Kit for the instrument. I have no problem with the electronics, however, I am not sure what kind of switch to use for switching from one sensor to the other. I guess an electro-magnetic relay is not the best choice, is it? Should I use a MOSFET? Which one? Another question is if both wires of the coils should be switched or if one is enough.

Maybe there is someone around who owns the Geometrics Gradiometer Kit and will allow me a peep inside the switching box.

Best regards
Magbird

[Unregistered]

G-856

I would be interested in purchasing your extra solenoid sensor for the G-856.

Could you supply me with photos and price.

Is it in working condition and does it leak any fluid? Thanks

[Magbird]

G-856

Hi,
I finished buliding the gradiometer, so I won't sell a single sensor. I have some Geometrics mags for sale:

-> G-816/826 (0.25nT, with modified display to show real nT value and with data memory, RS232 port). Will be finished in Jan-09.

-> G-856

-> G-856 gradiometer

I can equip any G-816/826 with memory/RS232

Contact: malte_ibs at yahoo.de

regards

[Unregistered]

Share???

Hi,
I also have a G856 and a spare sensor. Are you willing to share what you did to connect up the second sensor? I have no idea what is inside the gradiometer option.
Thanks,
FJ

[magbird]

Share

Hi,
you have to use the Sync-Line of the big connector on the console. This line activates a measurement. For switching from one sensor to the other I use a small relay in the switchbox. It is driven by a small microprocessor (ATtiny) that does the timing:

1. Press button on switch box -> trigger sync-line
2. wait for 4 seconds to take measurement of sensor A
3. switch relay to sensor B and wait a few ms
4. trigger sync-line
5. wait for 4 seconds to take measurement of sensor B
6. switch relay back to sensor A
Thats it.

You can for sure also use an analog timing IC like NE555 but the MC was easier for me and needs less parts. I can supply more info if you want.

Best regards
magbird

[n2000k]

Hi,
I finished buliding the gradiometer, so I won't sell a single sensor. I have some Geometrics mags for sale:

-> G-816/826 (0.25nT, with modified display to show real nT value and with data memory, RS232 port). Will be finished in Jan-09.

-> G-856

-> G-856 gradiometer

I can equip any G-816/826 with memory/RS232

Contact: malte_ibs at yahoo.de

regards

Are these items still available??