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3.2.1 3.2.1 Voltage Function (08-800-002/1)
The input for the voltage function is the setting of the three decade D to A converter, which
applies the scaled value of voltage to the precision integrator AR11/12. The other input to the
integrator is the scaled rectified value of the output, conducted to the integrator via the dotted path.
The inputs to the integrator are nulled by feedback as follows.
The precision integrator controls the amplitude of the voltage oscillator through modulator
AR12. The output of the oscillator at AR10-6 is amplified by the power amplifier consisting of AR6,
Q2, Q3, Q4, Q11 and Q12. The amplifier drives the transformer to boost the voltage to the output
level. The output is thus caused to track the setting of the D to A converter input.
3.2.2 Current Function (08-800-002/2)
The input to the current function is the setting of the D to A converter which has as its
reference input the constant 7.0711 volts AC output of the current oscillator, TP11. The scaled value
of current at TP3 of the CVA module is conducted to summing amplifier AR4, where it is compared
with the voltage across one of the precision shunts, derived from the differential amplifier AR8. The
current in the shunts is thereby caused to follow the setting of the D to A converter.
The output of AR4 is conducted to the current output amplifier consisting of AR9, Q1 and Q3
through Q10, and then to one of the three shunts; 10 ohm, 1 ohm, .1 ohm in value. The current is
then conducted to the current output terminals or to the current transformer and then to the output
terminals.
3.2.3 Phase Control Function (08-800-002/3)
The input to the phase control is the setting of the PF D to A converter. The output of the D
to A converter at AR8 is the value -(1 PF) 10 volts (selected by switch U7 for lag); the value +(1 PF)
10 volts is selected by switch U6 for leading PF.
The current oscillator output at AR2-6 is sliced by AR1 and 3 on the Phase Control and
Sense. The voltage output is sliced by AR9/10 and 14. IC1, 2, 3 and 4 constitute the phase detector,
which produces the lead or lag control to switches U4 and U5. The switches open to pass the portion
of the sine wave in the interval measured by the phase detector. The integrated value of the
truncated sine wave is equated to the value of (1 PF)x10 by the integrator which controls the phase of
the I oscillator through modulator AR3. Waveforms illustrating the function are shown in Figure 3-7
and Figure 3-8.
3.3 Controls
The Interface and Control Logic operates in two modes:
Local: The calibrator is under front panel control
Remote: The calibrator is under control of signals on IEEE 488 bus only
The Series 800 powers up in local mode. The remote mode is asserted when addressed as a
listener, by a software signal received via the IEEE-488 Interface. Figure 3-9 shows the flow of
signals in both modes.
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