System Configuration And Block Diagram - YOKOGAWA WT110 User Manual

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System Configuration and Block Diagram

System Configuration
Block Diagram
Model INPUT Section
253401 ELEMENT 1
253502 ELEMENT 1,3
253503
ELEMENT 1,2,3
VOLTAGE INPUT
CURRENT INPUT
IM 253401-01E
PT
Voltage
input
Equipment
under
Current
test
input
CT
Ext.
sensor
INPUT ELEMENT 1
A/D
ISO
interface
Zero Cross
Detector
LPF
A/D
ISO
Zero Cross
LPF Detector
EEPROM
INPUT ELEMENT 2
INPUT ELEMENT 3
This instrument consists of various sections: input (voltage input and current input circuits),
DSP, CPU, display and interface section.
In the voltage input circuit, the input voltage is formalized by a voltage divider and operational
amplifier, then sent to the A/D converter.
In the current input circuit, one shunt resistor is used to form a closed circuit. The voltage
between both ends of the shunt resistor is amplified and formalized by an operational amplifier
and then sent to the A/D converter. This method enables switching of the current range without
opening the current measurement circuit, so the current range can be switched while electricitiy
is supplied to the circuit. This also enables remote control via communications outputs.
The output from the A/D converter in the current input and voltage input circuits is sent to the
DSP (Digital Signal Processor) via a photo-isolator, which is used to provide insulation between
the current input circuit (or voltage circuit) and the DSP. One DSP is provided for each input
element (current/voltage). For example, a total of 3 DSP's are used for the three-phase, four-
wire model (model 253503). The DSP performs averaging of voltage, current and active power
for each sampled data sent from the A/D converter. After processing of a certain number of sets
of data has been completed, computation of apparent power, reactive power, power factor and
phase angle starts.
Computation results are then sent from the DSP to the CPU, where computation such as range
conversion, sigma computation and scaling is carried out. Control of display and outputs is also
performed by the CPU.
Digital
Input
either
power meter
one
WT110
(253401)
WT130
Input
(253502,253503)
either
one
SAMPLING
Bus
A/D
DSP
Arbiter
Lead/Lag
Detector
FREQUENCY
COUNTER × 2
CLOCK
HARMONICS
PLL
DMAC
RAM
(Option)
Contact / relay output
Analog output
Recorder
GP-IB or
Personal
RS-232-C
Computer
Ext. printer
or plotter
CPU
CPU
CLOCK
ROM
RAM
KEY&DISPLAY
CONTROLLER
GP-IB
or
RS-232-C
D/A OUTPUT
EEPROM
(Option)
COMPARATOR
Bus
(Option)
Arbiter
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