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2-2
IM 760301-01E
Block Diagram
Input element 2 to 4
Input element 1
Voltage input circuit
Volt. meas. input circuit
Freq. meas. input circuit
Element
2 to 4
DSP
Element 1
Delta
DSP
(option)
MATH-DSP
(option)
U
±
I
±
EXT
Current input circuit
A/D
zero cross
detection
Pulse
trans-
former
Peak
detection
A/D
zero cross
detection
Peak
detection
Line
filter
Pulse
trans-
former
Line
filter
Frequency
filter
CPU
8.4-inch
LCD
RGB output
(option)
Built-in printer
(option)
RS-232
(option)
PC card
GP-IB
Keys
(option)
Isolator D/A
Motor
DSP
Line
filter
Motor input circuit (option)
Isolator
Line
filter
Isolator
TORQUE
SPEED
Input peak detection circuit
Frequency
filter
A/D
zero cross
detection
Peak
detection
A/D
zero cross
detection
Peak
detection
USB port (PC)
(option)
USB port (peripheral
device) (option)
Ethernet
(option)
Input Signal Flow and Process
The input elements 1 through 4, consist of a voltage input circuit and a current input
circuit. The input circuits are mutually isolated. They are also isolated from the case.
The voltage signal that is applied to the voltage input terminal (U,
±
) is normalized using
the voltage divider of the voltage input circuit and an operational amplifier (OP AMP). It is
then input to a voltage A/D converter.
The current input circuit is equipped with two types of input terminals, a current input
terminal (I,
±
) and a current sensor input connector (EXT). Either one can be used at any
given time. The voltage signal from the current sensor that is received at the current
sensor input connector is normalized using the voltage divider and an operational
amplifier (OP AMP). It is then input to a current A/D converter. The current signal that is
applied to the current input terminal is converted to a voltage. Then, it is input to the
current A/D converter in the same fashion as the voltage signal from the current sensor.
The voltage signal that is input to the voltage A/D converter or current A/D converter is
converted to digital values at an interval of approximately 5
µ
s. The digital values are
isolated by the pulse transformer and passed to the DSP. In the DSP, the measured
values are derived based on the digital values. The measured values are then
transmitted to the CPU. Various computed values are determined from the measured
values. These measured values and computed values are displayed as measurement
functions of normal measurement, output through a D/A converter, or output through
communications.
The measurement functions of harmonic measurement (option) are derived in the
following manner. The voltage signal input to the A/D converter is converted to digital
values at a sampling frequency that is determined by the PLL source signal. The
measured value of each item of harmonic measurement is derived by performing an FFT
based on the converted digital values using the DSP.
2.1 System Configuration and Block Diagram
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