Free-Field Magnetic Field (B-dot) Sensors

Free-Field Magnetic Field (B-dot) Sensors

Description

PPM offers three different types of free-field sensor:

  • Multi-gap type: B10, B20, B60, B90 and B100 are precision multi-gap design free-space magnetic field sensors.
  • Full loop: the B-24 is a full loop magnetic sensor  – a very small portable device designed specifically for making high frequency free-field measurements.
  • Multi-turn: the MTB-2 is a multi-turn free-field B-dot sensor is equivalent to the AFWL model MTL-2.  Its 10-turn loop configuration has the same equivalent area as model B20 with a significant reduction in size.

Multi-gap type sensors

The B10, B20, B60, B90 and B100 are precision multi-gap design free-space magnetic field sensors. Each sensor consists of a conducting cylinder which contains four equally spaced longitudinal gap structures. The voltage developed across each gap is carried on pairs of 200 Ω transmission lines, which at opposite gaps are connected in parallel to 100 Ω cables. These cables in turn are connected to the 100 Ω twinax output cable. This design is effectively a half-turn loop driving the output connector. The gap and wiring configuration used causes any responses to electric fields to be cancelled and the sensor output signal to result from only magnetic fields.

These sensors should be supported by dielectric materials and placed no closer than two sensor diameters from conducting sensors.

B10-B100 multi-gap type free field sensors

 

 Equivalent Area (Aeq)Frequency Response (3 dB Point)Risetime (tr 10-90)Maximum Output (peak)Output Connector
B101 x 10-1> 120 MHz<3.0 ns± 5 kV100 Ω Twinax*
B201 x 10-2> 300 MHz<1.2 ns± 5 kV100 Ω Twinax*
B601 x 10-3> 840 MHz<0.42 ns± 2 kV2 SMA Male
B902 x 10-5~ 10 GHz<0.35 ns± 150 V2 SMA Male
B1001 x 10-4> 2.6 GHz<0.13 ns± 1.5 kV2 SMA Male
*=modified GR-874

Full loop type (for high frequency)

The PRODYN model B-24 is a full loop magnetic sensor that measures the time rate-of-change of a magnetic field. This very small portable device was designed specifically for making high frequency free-field measurements. For this type of measurement and because the sensor is fragile due to its size, it should be supported by dielectric materials and placed a minimum of two sensor diameters from conducting surface. The sensing area is encapsulated to provide breakdown resistance and protection from the environment. The sensor is a passive device; therefore, an external power source is not required. This sensor is only available in a radial output design.

Prodyn B24 B-Dot sensor

 Equivalent Area (Aeq)Frequency Response (3 dB Point)Risetime (tr 10-90)Maximum Output (peak)Output Connector
B249 x 10-6approx 8.5 GHz<0.041 ns± 500 VSMA (male)

Multi-turn type (high sensitivity/small size)

The MTB-2 is a multi-turn free-field B-dot sensor that produces a voltage output in response to a time variant B-field and is equivalent to the AFWL model MTL-2. This sensor was designed to have greater sensitivity in relation to it’s size. Its 10-turn loop configuration has the same equivalent area as model B20 with a significant reduction in size. The electrostatic shield minimises E-field drive and the internal loop resistors dampen high frequency resonances. The sensor output is differential and can be used with an appropriate balun.

This sensor can be ordered with either an axial or radial output direction. The standard output connector is GR twinaxial but other connector types can be ordered.

MTB-2 schematic with metric dimensions

 Equivalent Area (Aeq)Frequency Response (3 dB Point)Risetime (tr 10-90)Maximum Output (peak)Output Connector
MTB-21 x 10-2 m²>12.7 MHz<0.28 ns± 5 kVGR TCC (twinax)

Datasheets and Brochure