American Magnetics 420 Power Supply Programmer - Manual (Page 19)

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1 Introduction
1.1 Model 420 Features
The AMI Model 420 Digital Programmer is a sophisticated power supply
controller which allows an operator to manage a superconducting magnet
system with unprecedented accuracy and ease of use. The Model 420 is the
heart of a modern superconducting magnet system; when it is used in
conjunction with a four-quadrant power supply, it provides for a degree of
flexibility and accuracy previously unavailable in an economical
commercial product.
1.1.1 Digitally-Controlled
The Model 420 is controlled by a microcomputer-based controller which
controls all analog data conversion, display/keypad functions, communica-
tions I/O, generation of analog programming signals for the external power
supply, and control law computations. The Model 420 incorporates digital
signal processing (DSP) functions that provide for accurate control, low
drift, and flexibility of use.
1.1.2 Superior Resolution and Stability
The Model 420 Programmer utilizes high resolution converters to trans-
late signals between the analog and digital domains. Precision instrumen-
tation techniques and potentiometer-free designs are employed
throughout the instrument to ensure accurate signal translation for a wide
range of conditions. The magnet current is sampled at 20-bit resolution in
hardware and is software-programmable to 15-digits resolution. All pause
and hold functions are performed in the digital domain which provides for
excellent stability and drift (<0.01%) of the programmed magnetic field.
1.1.3 Intuitive Human-Interface Design
The Model 420 Programmer was designed so as to simplify the interface
where possible. All functions were analyzed and subsequently
programmed so that the most commonly used functions are addressed
with the least number of keystrokes. The menus are also presented in a
logical fashion so that the operation of the Model 420 is intuitive to the
user.
The provision of a velocity-sensitive rotary encoder on the front panel also
allows the operator to fine-adjust many of the operating parameters of the
magnet system.