Control Board
5-10
Force EZ-C Series Service Manual
Dosage Error Algorithm
The basis for the dosage error algorithm for the closed loop modes (bipolar, cut,
and the low 2 and low 3 settings) is a comparison between two microcontroller/
sensor sets:
•
backup current and voltage sensors, read by the main microcontroller (U5)
•
primary current and voltage sensors, read by the feedback microcontroller
(U11)
Each microcontroller monitors one set of sensors and calculates real-time output
current, voltage, and power. While the feedback microcontroller operates the
generator, the main microcontroller checks the values to make sure the main and
feedback microcontroller calculations agree.
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 and current calculated by the backup sensors are
less than 125% of the value calculated by the primary sensors. On passing this
test, the algorithm checks the feedback mode of the generator:
•
In current control mode, the current calculated by the backup sensors should
not deviate from the current calculated by the primary sensors by more than
50% of the value calculated by the primary sensors.
•
In power control mode, the power calculated by the backup sensors should not
be greater than 125% of the value calculated by the primary sensors.
•
In voltage control mode, the voltage calculated by the backup sensors should
not 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. It compares the current and voltage sensor analog values
to the previous readings to ensure that the sensor values are not constant or falling
while ECON is rising.
The basis for the dosage error algorithm for the open loop modes (the
low 1, high 1, and high 2 settings) is 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.
These tests detect power output while not activated, stuck or aberrant sensors, and
improperly delivered power. The dosage error firmware executes in less than one
second.
