NF FRA51602, Instruction Manual

Page: 22 / 286

1.3 Operating principles
1
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8
FRA 51602
a) OSC CKT
This is the oscillator that generates the measurement signal for the instrument. The synthesizer uses a
digital direct synthesis method to have a setting resolution of 10 µHz in the range from 10 µHz to 15 MHz.
The synthesizer features both immediate frequency change and phase continuity. This instrument is also
equipped with a function for stopping oscillation at 0° phase and a function for changing frequency at 0°
phase, and can thus suppress effects on the equipment under test to the minimum.
b) PREAMP CKT
This is the analysis module that comprises a variable attenuator, variable-gain amplifier, and an A/D
converter. It has two input channels (CH1 and CH2). The DC component of the input signal is removed and
the signal is amplified (or attenuated) to an appropriate level before 16-bit A/D conversion.
Both channels have a maximum input voltage of 600 V and are rated for MEASUREMENT CATEGORY II
(CAT II). (The maximum voltage for CAT III is 300 V).
The OSC output and the inputs for CH1 and CH2 are isolated from the enclosure and the terminals are
isolated from each other with an insulation rating of 600 V CAT II or 300 V CAT III. Although it is possible
to take measurements on circuits that are connected to the primary side of the mains, it is necessary to use
the rated voltage and over-voltage category.
c) MEASURE CPU CKT
This performs OSC CKT and PREAMP CKT configuration and control. It also performs discrete Fourier
transform (DFT) processing of the digital data after A/D conversion of the signal by PREAMP CKT,
conversion to gain and phase, and various types of error correction. The error-corrected measurement data
is sent to UI CPU CKT.
d) UI CPU CKT
This module displays the measurement data received from MEASURE CPU CKT on the LCD screen in
various graph formats. It also sends measurement commands to MEASURE CPU CKT according
specifications from the front panel and remote interfaces. The USB
-h
connector on the front panel is used
for connection of memory devices.
e) POWER SUPPLY CKT
In addition to supplying power to the digital modules and control module, this module provides a
high-impedance isolated power supply to CH1, CH2, and OSC.