NF FRA51602, Instruction Manual

Page: 148 / 286

4.4 Integration
4
-
18
FRA 51602
4.4 Integration
This instrument performs measurement processing as a discrete Fourier transform (DFT) in units of one
cycle of the measurement waveform. By nature, the DFT essentially removes noise and high-frequency
harmonics. However, if the signal component being measured is small relative to the noise, or if highly
accurate measurement is required, the accuracy of measurement can be improved by increasing the
integration period (the number of integrations).
White noise is reduced in rough proportion to the square root of the integration setting (number or duration
of integrations). Noise components other than the measurement frequency are also reduced by increasing
the integration setting. However, the time required for measurement increases in proportion to the number
of integrations.
■ Setting the integration mode
There are two integration modes: manual integration, in which the number of integrations is
predetermined, and automatic integration, in which the number of integrations is adjusted automatically
according to the measurement data.
Select
【
OSC
】－
[INTEGRATION MODE] .
[FIX] : Manual integration
[SHORT] : Automatic integration (short time)
[MED] : Automatic integration (medium time)
[LONG] : Automatic integration (long time)
● Manual integration
The normal setting is [FIX] . The integration is performed according to the number of times or the
duration that is set in [INTEGRATION] .
● Automatic integration
The number of integrations is determined by monitoring the variance of the measurement results (DFT
results). The integration is performed repeatedly in the order SHORT < MED < LONG until the
variance becomes small. Clean data is thus obtained, but the measurement time is long.
When the signal-to-noise ratio decreases only within a particular frequency range within the sweep
range, it may be possible to obtain clean data in a short time as the result of automatic integration.
However, because the number of integration times is determined on the basis of a statistic (variance),
the integration may end while the signal-to-noise ratio is insufficient or the integration may be repeated
more times than is necessary, depending on the nature of the signal being measured. (The integration