Free-Field Magnetic Field (B-Dot) Sensors

Free-Field Magnetic Field (B-Dot) Sensors

Description

PPM offer 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 as the same equivalent area as model B20 with a significant reduction in size.

Multi-gap type sensors

The B10, B20, 90 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 200Ω transmission lines, which at opposite gaps are connected in parallel to 100Ω cables. These cables in turn are connected to the 100ohm 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 not closed than two sensor diameters from conducting sensors.

B10-B100 multi-gap type free field sensors

 

 B10B20B60B90B100
Equivalent Area (Aeq)1 x 10-1 m21 x 10-2 m21 x 10-3 m22 x 10-5 m21 x 10-4 m2
Frequency Response (3 dB Point)> 120 MHz> 300 MHz840MHzapprox 10GHz>2.6GHz
Risetime (tr 10-90)<3.0 ns<1.2 ns<0.42ns<0.035ns<0.13ns
Maximum Output (peak)± 5 kV± 5 kV± 2kV± 150V± 1.5kV
Output Connector100Ω Twinax*100Ω Twinax*2 female 50Ω SMA/
100Ω twinax*
2 female 50Ω SMA/
100Ω twinax*
2 male 50Ω SMA
*=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

 B24
Equivalent Area (Aeq)9 x 10-6 m2
Frequency Response (3 dB Point)approx 8.5GHz
Risetime (tr 10-90)<0.041ns
Maximum Output (peak)± 500V
Output ConnectorSMA (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 as 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.

Prodyn MTB-2 B-Dot sensor

 MTB-2
Equivalent Area (Aeq)1 x 10-2 m2
Frequency Response (3 dB Point)>12.7MHz
Risetime (tr 10-90)<0.28ns
Maximum Output (peak)± 5kV
Output ConnectorGR TCC (twinax)

Datasheets

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Prodyn Free-Field Magnetic Field Sensors Datasheet – Multi-Gap Type

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Prodyn B-24 Magnetic Field Sensor Datasheet

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Prodyn MTB-2 Multi-Turn Magnetic Field Sensor Datasheet