4.12.1 Maximum Output Current
37
|
www.lakeshore.com
4.11 Zero Output
The
Zero Output
key on the front panel can be used to set the output current to 0 A.
When you press
Zero Output
, the current output will begin to ramp down using the
current ramp rate that you set in section 4.8. This key is equivalent to using
Output
Setting
and entering 0 A, except that it works even when the Model 648 is being pro-
grammed externally. Refer to section 4.7 to set the output current.
The current ramp rate applies only to the internal current output setting. When the
Model 648 is programmed externally, the drop to zero output (when the Zero Output key
is pressed) will be quite rapid (~1 second) and limited primarily by the magnet reactance
and the Model 648 voltage compliance limit. The voltage compliance LED may light
during the change.
4.12 Maximum
Setting Limits
The Model 648 offers a maximum setting limit for output current and ramp rate. Typ-
ical properties of the magnet will dictate these parameters. These maximum parame-
ters should be entered before the magnet system is used to prevent damage.
4.12.1 Maximum
Output Current
Maximum Output Current limits the output current that can be entered when using
the
Output Setting
key. This setting will only limit the internal output current setting.
If the output current is being programmed by an external voltage, then some external
provision must be made to insure that the programming voltage will never exceed the
desired output current. Refer to section 4.16 to setup the External Current Program-
ming mode.
To set the maximum output current limit press
Max Settings
. The first maximum set-
ting screen appears as a prompt for the maximum output current limit.
The maximum output current limit value can be set as high as 135.1000 A. This can be
used to compensate for variances in calibration. The output current is guaranteed to
reach a minimum of 135 A into a 0.5
)
load, but it may not be able to reach 135.1 A in all
circumstances.
Menu Navigation:
Max Settings
Q
(
0.0000 A to 135.0000 A
)
Default: 0.0000
Interface Command:
SETI
4.12.2 Maximum
Current Ramp Rate
Maximum Current Ramp Rate limits the maximum current ramp rate that can be
entered using the
Ramp Rate
key. This setting will only limit the internal output cur-
rent ramp setting. If ramp segments are being used, this setting will also limit the
ramp rate that can be set by a ramp segment. Refer to section 4.9 to setup Ramp Seg-
ments.
Menu Navigation:
Max Settings
Q
ENTER
Maximum current ramp rate (
0.0001 A/s to 50.000 A/s
)
Default: Enabled
Interface Command:
RS
4.13 Magnet
Water
The Model 648 provides power to control an external magnet water solenoid control
valve. The setup of the valve control is available in the magnet water menu. The four
menu selections are Auto, On, Off, and Disabled, with Auto being the default setting.
D
Auto mode:
the water valve will be energized when the power in the magnet
exceeds 200 W. When the power drops below 200 W, the valve will remain ener-
gized for an additional minute to remove any residual heat build-up.
D
On mode:
the valve will be energized whenever the power supply is on. This fea-
ture can be used when the system is first installed to purge air from the water
lines and magnet. It can also be used to turn on the water in advance of a test to
