Electro-Metrics EM-2115, Instruction Manual

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ELECTRO-METRICS EM-2115 2.0 OPERATING INSTRUCTIONS
(EM2115S2-14)
of the signal being measured is wider than the IF bandwidth of the receiver, a broadband meas-
urement is required.
To obtain a broadband reading, the Broadband Correction Factor (Appendix D, data ap-
plicable only for the EM-2115 with the serial number noted) is added to the digital meter indica-
tion. The resultant broadband measurement is in terms of dB(µV/MHz) (dB above one microvolt
per MHz of bandwidth).
NOTE: The procedure for determining if a signal response is
broadband or narrowband in character is given in 2.4.7.
In addition to broadband factors, correction factors for any pickup devices (antennas,
probes, etc.) must be added to the indicated amplitude level to obtain the actual input signal lev-
el.
2.4.6.2 Quasi-Peak Detector
The CISPR (Quasi-Peak) Specification (CISPR Publication 16) defines a system to meas-
ure the degrading effect that either a broadband or narrowband interferring signal may have on a
communication system without characterizing the interference as either broadband or narrow-
band. The CISPR Specification establishes the IF bandwidths verus frequency, quasi-peak detec-
tor rise and decay times, and the metering time constants. Refer to Table 1.4 (Page 1-9) for the
CISPR characteristics of the receiver.
The Quasi-Peak Detector is calibrated in terms of the equivalent rms value. For an un-
modulated CW signal, the Quasi-Peak amplitude measurement is identical to the rms amplitude
measurement. The Quasi-Peak measurement is in terms of dB(µV) and applies to both broadband
and narrowband signals. The measured amplitude of narrowband signals will be similar to Carri-
er detection, although a modulated signal may be up to 6 dB higher in Quasi-Peak.
The broadband indication depends on the repetition rate of the interfering signal and will
approach the Peak measurement as the repetition rate increases. For an isolated impulse, the
Quasi-Peak measurement may be more than 32 dB lower than the Peak measurement. Table 2.3
illustrates the CISPR Conversion Factors that are used for correlating the output level (in
dB(µV/MHz)) of an external Impulse Generator (I.G.) to the digital meter reading (in dB(µV)) of
the EM-2115 in the Quasi-Peak Detector mode. The table also gives an illustration of how far
below a peak measurement the Quasi-Peak measurement will be for various impulsive repetition
rates.