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Lake Shore Model 625 Superconducting MPS User’s Manual

Operation

4-5

4.4.3

Display Brightness

The vacuum fluorescent (VF) display on the Model 625 has four brightness settings between 100% and 25% that can be
changed from the front panel. The brightness setting changes the entire VF display but does not affect the LED
annunciators to the right of the display. Continuous use of the instrument at 100% brightness will reduce the operating
life of the display and brightness of 25% is recommended for most applications.

To change display brightness, continue from the remote voltage sense display screen or press

Display Setup

then

Enter

until the following display setup screen appears as a prompt for display brightness.

Display Setup

Select With °®

Brightness: 25 %

Use the

key to select brightness, 25%, 50%, 75%, or 100%. Press

Enter

to accept the new selection and return

to the normal display. Press

Escape

to cancel the new selection and return to the normal display.

4.5

SETTING OUTPUT CURRENT

The main purpose of the Model 625 Superconducting Power Supply is to supply a very precise and stable current to a
highly inductive load. Before setting output current,

make sure that the instrument is properly setup for the magnet

system that is being used

. This includes setting up the maximum output current, maximum compliance voltage limit,

maximum ramp rate, quench detection, and PSH parameters. When a new output current setting is entered, the supply
will ramp from the current setting to the new setting at the current ramp rate, unless limited by the compliance voltage.
The Ramping LED will be lit while the output current setting is ramping. When the output current setting is entered, it
will be limited in magnitude by the maximum current setting. Refer to Paragraph 4.11 to setup the maximum settings.

To change the output current setting when in current display mode, press the

Output Setting

key. The output current

setting value on the normal display will be highlighted to prompt for the new output current setting value.

Set:

+ 0.0000

Use the data entry keys to enter an output current setting value between –60.0000 and + 60.0000. Press

Enter

to accept

the new value. Press

Escape

to restart the setting sequence and enter a different value. Press

Escape

again to leave the

setting sequence.

NOTE:

The output current setting value can be set as high as ±60.1000 A. This can be used to compensate for current
loss due to high resistance leads and for variances in calibration. The output current is guaranteed to reach a
minimum of 60 A but may not be able to reach 60.1 A in all circumstances.

If the display mode is set to field display mode, then the output setting value is also in units of field, either kG or T.
Refer to Paragraph 4.13 to setup the field constant and units. Even when the output is in units of field, the other
parameters remain the same. The ramp rate is still in units of A/s and the maximum current setting is still used.

There are certain circumstances in which the current will not be allowed to change. This is done for safety and to protect
the magnet system. If the output current is going to be kept from changing, an error box will pop up explaining why the
new setting is going to be ignored. These error boxes are described below.

Change not allowed while

PSH is warming or cooling.