FUNCTION CHARACTERISTICS
18
NA016 - Manual - 05 - 2022
CPU board
This circuit board contains all the circuits necessary for performing the analogue and digital pro-
cessing of the signals.
Analog processing
The following are envisaged:
• Anti aliasing filter circuits, .
• Amplifier circuits for conditioning the input signals,
• Reference voltage adjustment circuits for the measurement A/D converter.
The relays usea a DSP processor operating at 40 MHzThe input currents are sampled at a frequency
of 64 samples per period by means of a dual conversion system which allows the attainment of infor-
mation pertaining to polarity and amplitude with high resolution. The measurement criterion allows
precise measurement of even those signals having a unidirectional component, such as transient
currents with overlapping exponential, which typically appear during faults.
The circuit board also houses the output relays with the corresponding command and control cir-
cuits, communication circuits, buttons, LCD display, LEDs and the key switch.
CPU
A 32 bit DSP is provided.
The following are envisaged:
• Real Time Clock circuits with oscillator and super capacitor,
• RS232 communication port,
• RS485 communication port,
Memories:
• Ram: high speed static memory
• Flash memory,
• EEprom memory: used for calibration data storage,
Input board
• Three CTs committed for phase currents acquisition,
• One CT committed for residual current acquisition.
The input circuits are suitable for 1 A or 5 A external CTs.
[1]
MMI (keyboard, LED and display)
The MMI module (Man Machine Interface) includes:
• An eight keys 8 keyboard,
• a backlight LCD display,
• Eight signalling LEDs,
• RS232 communication port.
Note 1 The phase and residual nominal currents must be adjusted by means dip-switch.
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