Using Interference Analyzers

The Agilent E7400 series Interference Analyzers have been used for periodic EMSA monitoring for many years and is considered the monitoring standard by the EMSA user community. The E7402 is one of the more cost-effective options of the E7400 series.

The NI-9770 RF card was designed to have the features of the Agilent E7402 that were used for EMI Monitoring but used less costly components.

The Agilent E7402 has a lower noise floor than the NI-9770 but both units have similar detection capabilities once the signal gets above the noise floor. The graph below compares field readings from both units.

NI-9770 card trends and Agilent E7402 periodic measurements have different levels of concern. The NI-9770 card uses the Power Spectrum, which is more sensitive to developing problems and can more easily detect issues that have not developed signals stronger than the local radio stations. The Agilent E7402 periodic measurement process uses the peak scan voltage.

The NI-9770 card has the following levels of concern for the areas of interest:

Recently, a generator was above 10,000 uV for about five years. A step change in level from 13,000 uV to 16,000 uV (Power Spectrum: 30 MHz – 100 MHz) was noted approximately three months before the unit tripped on stator ground. The issue was found in the Isolated Phase Bus: some cracked insulators and significant dirt contamination on other insulators.

For the Agilent E-7402, peak values of the spectrum are:

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