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Model 648 power push buttons
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CHAPTER 4:
Operation
Model 648 Electromagnet Power Supply
When the Model 648 is turned on, the display shows the Lake Shore logo and the
alarm beeper sounds briefly. After a few seconds, a “checking hardware” message will
appear in the center of the logo display while the instrument does an internal diag-
nostic to verify that everything is working. Most of the instrument setup parameter
values are retained when power is off with a few exceptions. The output current will
always be set to 0 A anytime the instrument is powered up. When the instrument is
powered on for the first time, parameter values are set to their defaults, as listed in
TABLE 4-4.
When initialization is complete, the instrument will begin its normal reading cycle.
Current and voltage readings should appear on the display. Any error messages will
appear in the center of the display. Messages listed in TABLE 6-2 are related to the
instrument hardware and may require help from Lake Shore service. The messages
listed in TABLE 6-3 are related to instrument operation and may be corrected with
user intervention. The Model 648 should be allowed to warm up for a minimum of 30
min to achieve rated accuracy.
4.3 Display
Definition
The Model 648 has an 8 line by 40 character vacuum fluorescent (VF) display capable
of showing both text and graphic images. The features displayed during normal oper-
ation include current measurement, voltage measurement, current programming,
ramp rate, magnet water status, internal water status, program mode, and internal
temperature. Other display configurations appear during parameter setting and data
entry operations. These displays are illustrated in their individual operation para-
graphs. A typical display is shown in FIGURE 4-3.
Model 648 display
4.4 LED
Annunciators
There are five LED annunciators on the front panel that are used to indicate the status
of the instrument. These provide easy verification of the operation of the instrument.
FIGURE 4-4 shows locations of the LEDs.
Model 648 LED descriptions
Fault
On when a hardware fault condition exists; blinking when a soft fault condition exists
Compliance
On when the maximum compliance voltage is reached
Power limit
On when the power in internal devices reaches the maximum limit
Ramping
On when the output current is ramping; blinking when ramp is paused
Remote
On when the instrument is in remote computer interface mode
FIGURE 4-2
FIGURE 4-3
TABLE 4-2