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| BCI probes from FCC and Bulk Current Injection Measurements
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| Bulk current injection (BCI) methods are used to evaluate the electromagnetic susceptibility of a wide range of electronic devices including automotive, avionics, computing, medical and telecommunications equipment. The BCI method simulates continuous wave currents developed in electrical conductors of equipment during normal operation of the equipment under test.
Applications
These conductors include the signal, control and power circuits of equipment being evaluated.
Bulk current injection conducted immunity test methods use RF transformers to inductively couple large RF currents into conductors linking parts of electronic systems. The injection probe acts as a multiple or single primary winding and the line or circuit under test acts as a secondary winding. Injection probes can be used over the entire frequency shown in the insertion loss curve accompanying each unit. There are three benefits for performing compliance testing using bulk current injection: The primary benefit is that BCI test results correlate well with radiated susceptibility test results. The design engineer can evaluate the affect of injected currents on the "System" or "Subsystem" under development and the relative immunity of different designs at the prototype stage of equipment development saving significant redesign time and cost. Third, conducted immunity testing can function as an integral part of a production quality assurance program. Quality assurance engineers can use BCI to perform conducted immunity tests on 100% of all critical circuits ensuring a high level of system compliance. |
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| Choosing a Bulk Current Injection Probe Bandwidth, efficiency, CW power rating, and the physical dimensions are the key parameters to be considered. The most important mechanical parameter is the size of the internal diameter or injecting "window". The internal diameter must be able to accommodate the size of the circuit under test including cable looms as well as individual cables. Fischer Custom Communications offers clamp-on injection probes with internal diameters ranging from 32 mm to 66 mm. Injection probes with an internal diameter of 40 mm can be used with signal and power cables of most commercial electronic equipment and systems. Injection probes with internal diameters of 66 mm are ideally suited for military and avionics equipment having large signal and power cable "looms". |
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Custom designs having larger than 66 mm internal diameter are available.
The external dimensions of the injection probe become important if the probe must be placed inside the equipment under test like a motor vehicle or aircraft.
The useable or operational bandwidth of the injection probe must overlap the frequency range under evaluation. When conducting tests in accord with RTCA/DO-l60 Section 20, the useable bandwidth of the injection probe must be 10 KHz to 400 MHz. Two injection probes are required to inject the specified current over the entire range.
The effectiveness of the injection probe over the operational bandwidth is determined by the probe's efficiency. The efficiency of the injection probe is a function of the attenuation or insertion loss. The insertion loss is the ratio in dB of the amplifier forward power to the power delivered by the injection probe to a calibration fixture and its loop impedance. To inject large CW currents with small amounts of amplifier power the injection probe must have a low attenuation. Injection of small currents requires lower levels of efficiency. Each Fischer Custom Communications injection probe comes with a serialized calibration chart. The CW power rating of injection probes influences the effectiveness of the probe's operation. Each probe has limitations on power handling capability. The probe's rating should be higher than the power required to inject the specified current. Fischer Custom Communications offers injection probes with CW power ratings ranging from 50 to750 watts CW. Fischer Custom Communications injection probes can operate at the rated CW power level for a minimum of 30 minutes.  Injection Probes from FCC |
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| Injection Probe Calibration Fixture Injection probe calibration fixtures are a part of the test equipment required by most of the Bulk Current Injection Test Procedure Specifications. Fischer Custom Communications Inc. offers three injection probe calibration fixtures allowing the user to quickly and easily calibrate the injection probe prior to performing the compliance testing. These calibration fixtures offer three important benefits.
Calibration fixtures for Injection Probes |
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