Fluke 96000 Series - Instrument Control; Power Supplies

96000 Series
Service Manual
2-6
The modulating waveform is generated by a 36-bit numerically controlled
oscillator (NCO) with a programmable wave table, but a dedicated A-D converter
is included to allow the instrument to accept an external analogue modulation
source.
Instrument Control
Overall control of instrument functions is provided by the Digital PCA which
accepts data from the Front Panel Assembly user interface. The Digital PCA
responds by setting control bits on the Synthesizer PCA, RF Output PCA and
27 GHz Control PCA (96270A), via an 8-bit multiplexed address/data bus.
Leveling Head control bits are accessed by a serial interface on the RF Output
PCA.
The 8-bit multiplexed address/data bus allows the Digital PCA to receive self-test
and status data from the Synthesizer PCA, RF Output PCA and 27 GHz Control
PCA (96270A). Leveling Head-specific calibration data stored within an
EEPROM device in the Leveling Head is accessed by the serial interface on the
RF Output PCA. Factory set data is held by EEPROM devices on the
Synthesizer PCA, Leveling Head and 27GHz Control PCA (96270A). The Digital
PCA also handles external data communication via the GPIB and RS232 ports.
Operating voltages for most of the Digital PCA are derived from the Power
Supply PCA and are ground (Earth) referenced. The floating RF Common
circuitry is powered via a ribbon connection to the Synthesizer PCA. Optical-
isolators on the Digital PCA allow the Synthesizer PCA, RF Output PCA and
27 GHZ Control PCA (96270A) to exchange floating multiplexed address/data
with the Digital PCA.
Power Supplies
Line power is fed to the SMPS via a Power Block module, accessed on the rear
panel. The SMPS is mounted in the Mains SMPS Assembly with the Power Block
module, rear cooling fan & line frequency optical isolation. The isolated line
frequency signal & SMPS power fail signal are routed to the Power Supply PCA.
The Power Block module has one line voltage setting & one rating for the fuses
fitted in L and N.
From the +48 V dc SMPS output, switch mode and linear techniques are used to
derive earth-referenced regulated DC outputs which include +5 V dc, -8.2 V dc,
+12 V dc, +20 V dc, and +30 V dc.
The +5 V dc supply is used to power the Digital PCA where a +3.3 V dc supply is
also derived, both for internal use and to power the Keypad PCA and color
display. The +12 V dc supply is routed to the Front Panel Assembly, with the
Digital PCA, where it can be switched under firmware control to provide power for
the display LED backlight.
The +30 V dc supply feeds a trapezoidal waveform generator, located on the
Power Supply PCA, which produces a differential pair of line locked, 60 V peak-
to-peak, 200/240Hz, flat-topped waveforms with controlled rise and fall times.