Advanced Energy RFG 1251 User Manual page 20

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Advanced Energy
Table 2-1. Block Diagram Explanation
(5) Power
Measurement System
(6) Control and Logic
2-4
This section provides stable, precise, analog signals representing
the forward and reflected power measured at the output
connector. The measurement system consists of a microstrip
directional coupler and two channels of processing electronics.
The directional coupler samples voltages that are proportional to
the square root of the forward and reflected power. It has a flat
coupling coefficient that provides accurate measurements into
any load. The processing electronics consist of an input filter, a
multiplier for squaring the voltage signals, a low-pass filter, and a
scaling OP AMP.
The measurement system provides inherent linearity and a wide
dynamic range. It is calibrated using a computerized test station.
Once calibrated, no adjustments are required or provided in this
module or in the rest of the unit.
The control and logic module accepts analog and digital
commands from the operator and processes internal feedback
signals to control the generator. It also provides status
information to the operator.
The control and logic module monitors the forward power signal
from the measurement system and compares it to the requested
setpoint. Any resulting error signal is used to adjust the variable 0
to 200 Vdc output of the power inverter (3) and hence the output
of the power amplifier (4B).
This module also provides the control of the water solenoid.
Theory 5706058-A