After several weeks of research and testing, we have now come to the conclusion that an unshielded coil design is only useful up to about 5 MHz.

The unshielded FESP 5139 does not provide sufficient suppression of sheath currents, especially in the higher frequency range. Furthermore, the suppression of parasitic E-field components is not sufficient to perform reproducible measurements with high accuracy up to 26 MHz.

Therefore, Schwarzbeck has decided to replace the FESP 5139 with a new shielded antenna, called HFRA 5164. This radiating loop is also 100% compliant to the standard IEC 61000-4-39 and it has the feature to be shielded. A suitable calibration jig to hold the HFRA 5164 and the FESP 5134-1 has been prepared too. 

More information to come soon!

The magnetic, handheld coil FESP 5139 was designed to generate defined magnetic field strength in the frequency range from DC up to 26 MHz. The main application is immunity testing against magnetic fields according to IEC 61000-4-39.

Depending on the current source characteristics magnetic fields up to 360 A/m can be generated for a short time. The generated magnetic field strength is proportional to the coil current. A distance ring allows a precise spacing of 50 mm between the coil and the EUT surface. Other distance rings can be used to scale the current field-strength ratio. The highest field-strength levels can be achieved using the shortest ring. There are further rings available on request in order to provide a certain scaling between coil current and magnetic field strength (e.g. 1 A coil current = 20 A/m field-strength).

Application as Sensor for Magnetic Fields:

The FESP 5139 can also be used to measure existing magnetic fields. For this purpose, the FESP 5139 is connected to a frequency selective 50 Ohm measuring instrument e.g. a spectrum analyzer or a measuring receiver.

Depending on the current source characteristics magnetic fields up to 360 A/m can be generated for a short time. The generated magnetic field strength is proportional to the coil current. A distance ring allows a precise spacing of 50 mm between the coil and the EUT surface. Other distance rings can be used to scale the current-field-strength ratio. The highest field-strength levels can be achieved using the shortest ring. There are further rings available on request in order to provide a certain scaling between coil current and magnetic field strength (e.g. 1 A coil current = 20 A/m field-strength). The main part of the generated magnetic field is perpendicular (orthogonal) to the EuT-surface, i.e. in the same direction as the handle. The achievable accuracy for generating defined magnetic fields depends on the accuracy of current measurements. In some cases (with moderate field strength requirements) it may be advisable to use a well-known series resistor and measure the voltage across this resistor. The resistor can be scaled in a way to obtain a convenient voltage reading which corresponds to the generated magnetic field. The larger the series resistor compared to the inductance, the more frequency independent characteristics will be achieved (but the efficiency of field-strength reduces). For applications above 10 MHz, we recommend the use of the coaxial sheath current choke MSS 9630

Specifications: