American Magnetics 430, Инструкции по установке, эксплуатации и обслуживанию

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PPENDIX
: S
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AMPLE
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ODE
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19
The Model 430 also features the ability to operate as a short-sample
controller.
Short-sample
refers to samples of superconducting wires of
relatively short length as compared to lengths required for a wound
magnet, typically tested in the presence of various background magnetic
field levels. The short-sample test is designed to determine critical
current density limits for various field levels for the wire sample.
In the Short-Sample Mode, the Model 430 commands a connected
power supply in voltage-controls-current mode, i.e. the Program Out
connector (see page 198) outputs a voltage that corresponds to the
current output limit of a connected power supply.
The connected power
supply must support remote current limit programming by external
analog voltage.
CAUTION
The Short-Sample Mode includes a sample quench
detection feature. It is recommended that the sample
quench detection always be ON and that voltage taps across
the sample be connected to Auxiliary Input 2. It is possible
to destroy a sample (via overheating) if the Model 430 is
allowed to continue ramping or hold a current for a sample
that has quenched. Samples should not be left unattended
when actively ramping the sample current.
If the sample has quenched, the Model 430 will indicate the
sample current at which the quench was detected and
immediately command and hold the supply output current
at 0 A until the sample quench detection state is cleared.
The typical system setup for short-sample testing will require a data
acquisition computer to query and record the sample voltage vs. sample
current and an application to plot the real-time result.
In Short-Sample Mode several features of the Model 430 applicable only
to operation with a magnet are disabled. The changes include:
• All menu items associated with the Persistent Switch operation are removed.
• The Voltage Limit function is removed.
• The units display for current is always amperes since
there is no magnet
connected to the 430
with an associated coil constant (only the short-sam-
ple).
• The sample voltage is measured via Auxiliary Input 2 (see page 202) and is
reported in the default display as
Vss
in microvolts. An external gain factor of
19. Contact an AMI Technical Support Representative for details on how the Short-Sample Mode
can be enabled and the latest data acquisition options for microvolt sampling.