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Description of the semi-anechoic chamber

The semi-anechoic chamber consists in a shielded chamber made up of galvanized steel panels and covered inside with ferrite tiles and absorbent cones, in order to prevent reflection of the electromagnetic field.

The semi-anechoic chamber has two intake doors, both with knife-blade double shielding gaskets on the entire perimeter: a front part that opens into the A area with a 2.1x2.6 m² opening for large equipment (i.e. electrical control panels) and a service door with a 0.8x2 m² opening into the D area for personnel.

The chamber is echo-proofed with ferrite tiles on the four sidewalls (5.4 m high) and the ceiling. It is also equipped with hybrid absorption panels (ferrite tiles with pyramid-shaped resistant absorbers) for the floor and other sensitive internal areas.

The electric power supplies in the chamber (63 A three-phase and various single-phases) are adequately filtered outside. There are three technical panels with 1" wave-guides and cable/fiber optics runs. There are also eight honeycomb ventilation panels with flanges. The chamber is also equipped with a smoke detector, emergency lighting and interlock switches for safety, and a closed-circuit video camera system.

Inside there is a 2 m diameter motorized rotating table (maximum load 1000 kg) and an automatic antenna positioner for heights from 1 m to 4 m.

The chamber acceptance measurements were carried out by independent external bodies. The shielding measurements were conducted in accordance with MIL-STD 285, consistently obtaining values higher than 100 dB of attenuation.

The field uniformity measurements were taken in accordance with the procedure set forth in the latest edition of the IEC 61000-4-3 standard on 16 measurement points for a testing distance of 3 m (18 V/m) and 1 m (54 V/m), obtaining values that do not differ by -0 dB / +6 dB from the reference field value for more than 75% of the points on the entire band.

The NSA (Normalized Site Attenuation) measurements were taken using the cylinder method, from 30 MHz up to 1 GHz, measuring chamber attenuation by horizontally and vertically polarized antenna that always differs significantly less than 4 dB from the attenuation value at an ideal site.

These measurements confirm that the chamber is suitable for hosting full-compliance radiated immunity tests and radiated emission measurements in accordance with the CISPR standards.

Although radiated emission pre-conformity tests can be conducted in completely anechoic chambers with compact dimensions (or also TEM compartments and reverberating chambers), a large chamber like the one used at the ABB Dalmine factory is the instrument recommended by the regulations and it is used as a reference in the event of dispute.

Last page update: 2016.12.15 - Rev.: 1.0