Closed Loop Magnet Control
Group3 Controller Module + Analog Hall
Enhance stability by employing closed loop magnet control
Communications on DeviceNet - the industrial control
Communications on fiber optics - for high noise/high
Group3 Analog Hall Probe
Hall element, corrected for temperature and non-linearity. Fixed
probe or flexible cable. Custom design for OEMs possible.
The Group3 controllers - the CNA and DNA - have a built-in PID algorithm,
that allows them to perform local closed loop control. A controller, combined
with a Group3 analog Hall probe forms a compact, inexpensive way to implement
closed loop magnet control. The computer only needs to send the desired field
value - the controller will drive the power supply to steadily maintain that
field setting. The magnet and power supply becomes a simple "set and
forget" system, relieving the control computer and the communications
network of any ongoing control or supervision.
Two controller modules are offered - the CNA is part of the Group3 Control
system, and communicates via fiber optic cables to a Group3 card in the
computer. The DNA communicates on a DeviceNet network, the standard for
The Group3 Hall probe produces an analog voltage as its output signal, corrected
for temperature effects and non-linearities, producing a signal accurate to
within 0.05%, from -1 to +1 T, over 10 to 50 deg C. Group3 can offer
different field and temperature ranges, and custom probe dimensions.
Advantages of Closed Loop control - stability and repeatability
Closed loop control, with the appropriate sensor,
provides much greater stability.
If the magnetic field is controlled by setting the current of the power
supply, then as the magnet or supply temperature changes the current can
vary - so the field will deviate from its desired setting. If you are
measuring the field directly then you can hold the field constant, despite
This can have the big spin-off that you no longer need a very tightly
regulated power supply, and you don't need very precise temperature
stability in it either reducing the cost of the power supply considerably.
Stability is of particular interest in keeping a beam on target for a long
period, and is vital for big ring magnet systems.
Closed loop control will also give much better
If you ask for a particular field, that is what you get, no matter what
the temperature is, or was, and no matter what the history of the magnet.
Closed loop control overcomes temperature and hysteresis effects.
In a production environment the repeatability of field can speed up
switching between ion species or energies. If you ask for the same field as
last time, you know the beam will be in the right place. It is almost vital
if a machine wants to be able to operate on a recipe" type system,
VI Control Systems is a Factory Authorized Distributor for
Group3 Control and Analog Hall Probes.
Group3 Technology Ltd.
2 Charann Place, Auckland 7
P0 Box 71 111, Rosebank, Auckland, New Zealand
Phone +64 9 828-3358 Fax +64 9 828-3357
For further information contact
Neal Pederson at firstname.lastname@example.org
VI Control Systems Ltd., 2173 Deer
Trail, Los Alamos, NM 87544
Tel: (505) 662-1461, Fax: (866) 422-2931
and Created by VI Control Systems Ltd.
Copyright © 2005 All Rights Reserved.