Solved? - Hall effect probe for superconducting magnets

[ChristofferB]

Hi all!

I've been given a gaussmeter from my uni, a 70's vintage Systron Donner 3101.

A probe came along with it, but the probe is clearly from a different instrument, since it has a vastly different connector.

I'd like to try and get the probe tested before messing with the huge rack instrument.

Here is what is known:

 - It's a flat ceramic chip hall effect device on the end of a probe, model and manufacturer has been too smudged to read. Probe is potted.



 - The connector reveals 3 pairs of leads and a shield. I believe the pairs to be coaxial with individual shield:



Connector pin wire colors:

       - White + Black
       - Red + Black
       - Green + Black
     
       - Cable shield

       -None of the black wires are connected to each other or to main cable shield.


A hall effect device needs a current between two ports, and a voltage differential is extracted via two others:



Since a pin is lacking for that, it stands to reason the current supply might be using its shield (black wire?) as return,

and the two remaining colored wires are V+ and V-

How will I go about testing this? What voltages/currents are usually used with naked Hall effect devices? Keep in mind, I believe modern Hall effect devices already has a regulator and current reference built in.

 

Thanks in advance!

[ChristofferB]

Ok so I've stripped the probe element, and it seems 6 wires lead to it. There is a small black nodule at the silicone strain relief right by the sensor which could be a thermistor, as a hall device really only should need 4 wires. I'm considering breaking these out to some headers for easier access, but it still doesnt solve the issue of pinout...

Is there any semiconductor junctions in a hall device that can be checked with a diode checker?

[ChristofferB]

2 of the leads are almost certainly an NTC - at room temp. They have a resistance between them of 1.8K, when freezed with a freeze spray it shoots up over 10K.  (white+black pair)

Makes sense for a probe for a cryogenic magnet! That leaves only the 4 wires that would be expected!

[ChristofferB]

Okay, almost got it figured out!

Applying +5V through an 1K resistor to the green+black pair gives a voltage between 0 and 1 mV out on the red/black pair when a powerful neodymium magnet is brought near.

I still have no idea what voltages/currents is expected for a device like this, although I think sensitivity is set with the bias current.