Walker Scientific MG-3D Gaussmeter

Brooke Clarke 2013

Walker Scientific MG-3D Gaussmeter
Walker Scientific MG-3D Gaussmeter



When working with permanent magnets as well as electromagnets it would be helpful to know the magnetic field strength.  I've received the meter and the probe is on the way.  A common problem is that you can find the meters for sale, but they are missing the probes so I hope to figure out how to make a probe.  Another common problem is the lack of a manual.  If you have any documentation on the MG-3D please let me know.



The Amphenol 14S-6S six position sockets on the front and back panel are wired in parallel.  All 6 terminals are used for both sockets.
Using the F.W. Bell 640 manual as a proxy for this unit I would expect the probe to use 2 wires for driving the Hall sensor, 2 wires to read the sensor output and 2 wires for a temperature sensor for compensation.

If the probe is wired the same as the F.W. Bell probe then this is the pinout.
Note: the FW Bell 640 and it looks like the Walker MG-3D both use an AC drive signal to the Hall Device.

Hall Drive Current
Thermistor Return
Gain set resistor
Hall Voltage Out
Hall Drive Return
Hall Voltage Out
Thermistor Drive
Gain set resistor
Pins A & D Hall Drive form Rigol Scope without a probe connected.
About 5 Volts P-P at about 5 kHz (4.6 kHz ).
Walker Scientific MG-3D Gaussmeter Pins A &
                D Hall Drive

Pin A is at the top next to the key and the socket pins are lettered counter clockwise.
Note the sensitivity of Hall sensors varies with each individual unit so both zero and full scale need to be calibrated for the combination of probe and meter.


2260589 Magnetic flux meter, Smith, George S, Oct 28, 1941, 324/252, 324/117.00H - Hall Sensor

Cited by the following patents:
Citing Patent Filing date Publication date Applicant Title
US2599550 * Apr 27, 1949 Jun 10, 1952 Robert Fraser Fluxmeter and probe therefor
US2649569 * Sep 28, 1950 Aug 18, 1953 Bell Telephone Labor Inc Semiconductor magnetoresistive device
US2712601 * Jun 6, 1952 Jul 5, 1955 Voltohm Processes Ltd Mechanical-electrical transducer
US2946955 * Aug 25, 1954 Jul 26, 1960 Siemens Ag Measuring apparatus comprising a magnetic field-responsive resistor as a condition-responsive element
US3064185 * Aug 17, 1944 Nov 13, 1962 Bell Telephone Labor Inc Magnetic gradiometer system
US4517515 * Jun 3, 1981 May 14, 1985 The United States Of America As Represented By The Secretary Of The Navy Magnetometer with a solid-state magnetic-field sensing means
US5336998 * Jun 22, 1992 Aug 9, 1994 United States Pipe And Foundry Company Sensor for detecting faults in a magnetized ferrous object using hall effect elements
US8212513 Sep 22, 2009 Jul 3, 2012 Brose Fahrzeugteile Gmbh & Co. Kommanditgesellschaft, Hallstadt Method and device for detecting the rotation of a brush-operated d.c. motor
DE1145367B * Sep 21, 1953 Mar 14, 1963 Siemens Ag Einrichtung zur Messung des Quotienten zweier technisch-physikalischer Groessen
DE1157797B * Jan 8, 1954 Nov 21, 1963 Siemens Ag Einrichtung zur Messung des Quotienten zweier technisch-physikalischer Groessen mit Hilfe magnetfeldabhaengiger Widerstandskoerper und eines Verstaerkers
EP0238110A1 * Feb 12, 1987 Sep 23, 1987 Philips Electronics N.V. Magnetic head with magnetoresistive element


F.W. Bell 640 Incremental Gaussmeter
DC Permanent Magnet Motors


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