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(19) Output Indicator
When output is enabled, the output indicator will light.
(20) Power Switch
To turn on /off 72-7675.
(25) “COARSE” Key
Coarse/Fine adjustment selection key.
(26) “RANGE” Key
For the high/low output voltage’s range selection.
(29) “A” Key
Ammeter selection key of multimeter LED display
(30) “W” Key
Wattage meter selection key of multimeter LED display.
(31) “PF” Key
Power factor meter selection key of multimeter LED display.
(32) “LOCK” Key
Lock/Unlock keyboard selection key.
(33) Lock Indicator
The lock indicator lights to indicate the keyboard is locked. All
other keys except ‘RESET’ are disabled.
(34) Outlet
Output socket
Caution: The maximum AC voltage is up to 300V. Do
not touch the output sockets when the OUTPUT
indicator appears lit.
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5. CIRCUIT PRINCIPLE
This power supply is controlled by CPU and operated via
keyboard. The unit is fully digital controlled.
The input isolation transformer has been applied to isolate the city
power and step down the input voltage for appropriate applications.
The main AC power is rectified and filtered to become a very smooth
DC source for power amplifier. Sine wave form is generated by the
digital synthesizer and filtered by a very high impedance filter.
Therefore, the sine wave form will be very stable and the distortion
will be reduced.
The unit has two voltage feedback systems. One is analog
feedback system for quick response (within 100us), and the
regulation will be located in the range of
±
5%. The other is digital
feedback system. The system will read the output voltage and
compare with the settings. The accuracy of Output voltage will be
limited in the range of
±
0.1V.
The sine wave signal is amplified by power amplifier. The power
amplifier provides a very clean and low distortion sine wave to the
output of APS series through the output transformer. The offset and
calibration data of instrumentation are stored in the EEPROM. The
instrumentation will be calibrated automatically when the unit is
switched on. True RMS circuit is applied for the voltmeter and
ammeter. The value of LED display is true RMS value.
For easy operation, the power supply has a EEPROM memory.
The EEPROM will memorize the latest data settings automatically
after the unit has been switched off. When the unit is switched on
again, the CPU will read the data from the EEPROM and provide the
same output value as the previous setting. It is unnecessary to reset
the data after the unit has been turned off.
