Lake Shore 625, User Manual

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Lake Shore Model 625 Superconducting MPS User’s Manual
3-6 Installation
3.6.2 Remote Inhibit
The Remote Inhibit connection on the Digital I/O connector is an input that instructs the power supply to immediately set
the output current to 0 A. This input allows an external device to immediately shut off the output current of the supply in
case of a failure. This input is normally tied to an external quench detection circuit, the fault output of a second power
supply, or an emergency shut down button. This function will only set the output current to zero, so if the magnet is still
charged, it will discharge at a rate determined by the compliance voltage limit. The Remote Inhibit input is TTL
compatible and a logic low will activate it. The signal is internally pulled up to allow operation with a simple switch
closure. Refer to Figure 3-5.
Figure 3-5. Remote Inhibit and Trigger In Operation
3.6.3 Trigger In
The Trigger In connection on the Digital I/O connector is an input that is used to start an output current ramp. The trigger
can only be armed from the computer interface using the
TRIG command to setup a new output current setpoint. When
the Trigger In line is activated, the power supply will begin ramping to the new setpoint. Once the instrument has been
triggered, the
TRIG command needs to be sent again along with a new setpoint to rearm the trigger. The Trigger In input
is TTL compatible and a logic low will activate it. The signal is internally pulled up to allow operation with a simple
switch closure. Refer to Figure 3-5.
3.7 PERSISTENT SWITCH HEATER OUTPUT
The persistent switch heater output is a controlled DC current source capable of sourcing up to 125 mA with a jumper
selectable compliance voltage limit of 15 V or 24 V. The default setting is 24V. Refer to Paragraph 7.11 to configure the
compliance voltage limit of the persistent switch heater output. The actual voltage compliance limit is dependant on load
but guaranteed to be at least 12 V or 21 V depending on the setting. The heater output current is software settable in
1 mA steps from 10 to 125 mA. Typically, the magnet manufacturer specifies the persistent switch heater current. The
minimum load that the persistent switch heater can drive is 10

If the persistent switch heater is less than 10

a series
resistance needs to be added or else the PSH circuit will falsely detect a short circuit. Refer to Paragraph 4.14 to setup the
persistent switch heater.
Heater Output.bmp
Figure 3-6. Persistent Switch Heater Output Connector
3.7.1 Heater Output Connection
BNC receptacle provides connections for the persistent switch heater output. Signal is carried on the center conductor
and heater common is on the outer conductor. The heater output has a maximum voltage of 24 V and can source
125 mA. Mating connector not included.
3.7.2 Heater Output Cabling
Coaxial cable is recommended for the heater output, outside of the test dewar. The center conductor should be large
enough to carry the maximum 125 mA current to prevent accidental burn out of the conductor.