Agilent Technologies G1313A, Reference Manual

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Theory of Operation
Autosampler Main Board (ASM)
signal. The leak converter consists of a PTC (for leak sensing) and an NTC
(for ambient-temperature compensation). This configuration ensures
ambient temperature changes do not affect the leak-sensing circuit.
Fan Drive
The fan speed (two speeds are possible) is controlled by the main
processor according to the internal heat distribution inside the module.
The fan provides a PWM signal which is proportional to the revolution.
This fan status signal is used for diagnostics.
Electronic Fuses
The circuits that are connected to + 36 V are fused on the board
electronically.
Onboard Battery
An onboard lithium battery buffers the electronic memories when the
module is turned off. For safety information on lithium batteries see
“Lithium Batteries Information” on page 282.
Autosampler-Specific Electronics
The autosampler specific functions provided by the electronics are:
• closed loop control of four axis vial handling servos
• electric valve control
• Needle unit control
• metering device control
Transport Unit Control
The transport drive electronics use current-controlled pulse-width
modulation (PWM) to drive the X, Z,
θ
, and gripper motors in closed-loop
servo control mode. Dedicated electronics in the SGS L6506 provide the
current-control loop. Commutation is done in FPGA logic. SGS L6201 SMT
output drivers are used for all four stepper motors. Motor encoder signals
are connected to the ASIC where the encoder quadrature decoded clock
and the up/down signal are used in the FPGA to provide instantaneous
stepper motor commutation with respect to the motor rotor position.
Wiring between the autosampler main board (ASM) and the motors and
encoders uses a flat-band cable (64 pin) and a flex board on which 10