Speake & Co have been manufacturing and supplying their unique range of Magnetic Field Sensors designed by the late Dr Richard Noble, since 1995. The sensors themselves being augmented by a series of ASICS (Application Specific Integrated Circuits) to facilitate specific applications. e.g. gaussmeters, vehicle detectors, compasses, magnetometers and gradiometers

FGM - 1

This is a miniature version of the original standard FGM-3 type of sensor. It is essentially a three terminal device, (Gnd., +5 volts and Output) but a fourth terminal has been added which gives access to an internal over wound coil. This coil can be used to alter the zero field output frequency or as a feedback coil for linearity improvement. (see application notes). The output is in the form of a robust 5 volt rectangular pulse, whose period varies in proportion to the field along the principle axis of the device. Field Range + 0.5 oersted ( + 50 micro-tesla).

FGM - 2

This consists of two FGM-1 devices moulded into a circular package at right angles to one another, intended for use in field vector magnitude and direction finding systems. It can be used in two dimensional compass systems and in conjunction with an additional FGM-1, in three dimensional systems such as virtual reality and antenna orientation.

FGM - 3

This is the original larger version of the sensor, (60 mm long x 15 mm diameter) which has a somewhat higher sensitivity making it more suitable in some applications where size is not important. It has the same type of output as the other devices. Field Range + 0.5 oersted ( + 70 micro-tesla).


Field Nulling/Gaussmeter Device This is a dedicated chip designed to provide the hardware required to use the sensors in field nulling systems, such as removing the effect of interfering external magnetic fields on sensitive equipment. It has been used successfully, for example, in dramatically improving the performance of colour VDUs in difficult environments. In this context it works in conjunction with external field nulling coils around the sensitive area. In conjunction with the internal over wound coils in the sensors it can also be used to make Gaussmeters with high linearity and switched ranges. Package: 18 pin dual-in-line.


Vehicle Detector Device - This chip provides the hardware to make, with few external components, a vehicle detector for both fixed and portable use. It can be used, for example, in vehicle detection and census projects, traffic management, car park occupancy sensing and vehicle theft alarm systems. Equally, at closer ranges with smaller ferrous metal objects, it can be used for conveyor belt counting or proximity detection. Package: 18 pin dual-in-line.


Compass Chip - This chip provides the complex hardware needed to make a self calibrating, precision, accuracy bolt-down orientation compass, suitable for rotating platforms or aerials, etc. It has an RS232 output and a serial output for a direct digital display. It compensates for surrounding magnetic material and for tilt errors in the bolt-down mode. Suitably gimballed it could be used for applications other than the bolt-down type. Its many features cannot be described in this short summary and the full application note should be referred to for details. It is used in conjunction with an FGM-2 sensor. Package: 40 pin dual-in-line.


Magnetometer - This chip provides the hardware to make, with few external components, a highly sensitive earth field magnetometer for both fixed or portable use. It integrates the variations in the field over approximately eight second intervals and gives an extremely sensitive response to tiny variations. Of particular interest to radio amateurs and amateur astronomers in solar flare and propagation studies, it can also be used in laboratory type magnetometer configurations for ferrous metal measurements and contamination detection techniques. Package: 18 pin dual-in-line.


Gradiometer Device - This chip provides the hardware to make, with few external components, and two FGM type sensors a sensitive gradiometer for the detection of local field gradients or anomalies, caused by buried ferrous objects or larger scale changes in rock formation, etc. Used in the most sensitive configuration and with appropriate calibration technique, it may be of special interest to archaeologists or mineral surveyors. At a lower level it can be used in beachcombing and mine detection, finding the "pig in the pipe", cable current detection and remote shaft rotation sensing. Package: 18 pin dual-in-line.