Bruker Fourier 300 - Intelligent Devices with Can-Bus; Lock System; Variable Temperature Unit (VTU)

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Z31980_00_03
Design and Function
plane.
The main board receives only 28Vdc from the central 28V PSU and generates all the
other voltages it requires on board.
5.3.1.2 Lock System
The Lock System comprises three unit that are mounted together on one module:
• Lock-Board (transmit and receive)
• Lock Power Attenuator
• 2H Preamplifier
The lock board generates continuous small flip angle pulses at nominal 1 kHz rate. The
lock transmit power can be varied in the range from 0dBm to -30 dBm using the separate
digital attenuator. The receiver used a 50 MHz ADC to digitally down-convert the FID
using the same principle as on the main board. The thus obtained real part of the FID is
then used for the lock monitor, whereas the imaginary part is used to track the field,
using a digital P+I control.
The lock operates on a field locking principle, using the H0 Coil of the BOSS1 Shim Sys-
tem. The total range of the lock is around 20 kHz (as measured on 1H). This is controlled
by a 12-bit coarse DAC for range selection and a 12-bit fine DAC which does the actual
field regulation. The resolution of the fine DAC is about 0.025 Hz per DAC Step. In case
of magnet drift, the system has an “auto-range” function. i.e. when the fine DAC gets to
below 500 or above 3500, the coarse DAC is incremented or decremented by one step,
to bring the fine DAC back nearer the center of its operating region.
The two DAC voltages are fed to the shim board where they are scaled and added. A
current driver provides the driver current for the H0 coil.
The Lock board receives only 28Vdc from the central 28V PSU and generates all the
other voltages it requires on board.
5.3.1.3 Variable Temperature Unit (VTU)
The VTU is uses to control the sample temperature. The heater and thermocouple con-
nections are fully compatible with the BVT3000. It supports Thermocouple Types T and
K but unlike the BVT3000 it has an internal electronic cold junction compensation, which
means that ambient temperature variations do not affect the reading. The gas flow regu-
lation is done using 4 digital valves which allow 16 gas flow settings from 0 to 2000/h.
The recommended gas flow for the Fourier “one for all” probe is between 670 and 800 l/
h. For setting PID values please refer to the VTU web server description.
5.3.2 Intelligent Devices with Can-Bus
• 2 x Shim Boards (12 Channels each + H0 Control) – Slave of Main Board
• Peripheral Control Board (Spin, Lift, Helium Level Control, Sample Status) – Slave
of VTU