Control Board
4-10 Force FX-8C Service Manual
serial port. The serial port is configured to 9600 baud, 8 data bits, 1 stop
bit, with no parity. This timing is derived from the main microcontroller
oscillator frequency of 11.0592 MHz.
The control board serial port signals connect to the Power Supply/
RF board through the 96-pin connector. The signals are then connected to
the 9-pin serial port connector on the Power Supply/RF board.
Dosage Error Algorithm
Dosage Error Algorithm for Closed-Loop Modes
The dosage error algorithm for the closed-loop modes (bipolar and cut) is
based on a comparison between the actual power as calculated by the
main microcontroller (U5) using the backup sensors and the maximum
allowed power. While the feedback microcontroller is operating the
generator output, the main microcontroller calculates and checks the
values to make sure the feedback microcontroller is operating the
generator properly.
In a closed loop mode, there is a 500 ms delay before the dosage error
algorithm monitors the RMS output of the generator. After the delay, the
algorithm first checks to see that the voltage, current, and power
calculated by the backup sensors are less than 125% of the value
calculated by the primary sensors. On passing this test, the feedback mode
of the generator is taken into account.
• In current control mode, the current calculated by the backup sensors
is not allowed to deviate from the current calculated by the primary
sensors by more than 50% of the value calculated by the primary
sensors.
• In voltage control mode, the voltage calculated by the backup sensors
is not allowed to deviate from the voltage calculated by the primary
sensors by more than 50% of the value calculated by the primary
sensors.
During closed loop activation, the main microcontroller continually
checks for broken backup sensors. The current and voltage sensor analog
values are compared to the previous readings to ensure that the sensor
values are not constant or falling while ECON is rising.
When the generator drops into spark control, the software makes
allowances for the shift in frequency. The voltage sensor returns a value
that is approximately 20–25% high, and the rms value calculated for the
voltage sensor is reduced by 25%. The current sensor returns a value that
is approximately 10–15% low, and the rms value calculated for the current
sensor is increased by 12.5%.
The dosage error algorithm for the open loop modes (coag) is based on the
ECON calculated for the mode. The main microcontroller calculates an
ECON that represents 125% of the front panel power setting and verifies
that SYS_ECON and HV_SEN do not exceed this value while the
generator is activated.
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