American Magnetics 286 Multi-Sensor Liquid Level Instrument (CE-Marked) - Manual (Page 23)

9
Introduction
Controller Modes Description: Pre-Cool Mode
1.5.3 Pre-Cool Mode
The pre-cool mode, as illustrated in Figure 1-4, provides for cooling of a
cryogen transfer line before opening the transfer line to the controlled
dewar. The A and B setpoints for Channel 1 function as the liquid level
control band for the controlled dewar. AC Output 1 controls a fill valve for
the controlled dewar, while AC Output 2 controls a vent valve. Channel 2
is unavailable in the pre-cool mode.
When a fill cycle is initiated, the vent valve is initially opened for a user-
programmed time, after which the vent valve is closed and the fill valve to
the controlled dewar is opened. During the time the vent valve is open, the
cryogen cools the transfer line, so that there is a minimal amount of
cryogen gas entering the controlled dewar once the fill valve is opened.
LINE: 50-60 Hz, 4.2A MAX
100-120 V 200-240 V
!
C D
B A
SENSOR INPUTS
COMMUNICATIONS
LINE VOLTAGE, EACH 2A MAX
1 2
J5A
J5B
(OSC REQ'D) (OSC REQ'D)
Storage Vessel
Controlled
Dewar
Fill Valve
Model 286
Vent Valve
Vented Gas
Pre-Cooled Transfer Line
Figure 1-4. Pre-cool mode diagram illustrating one storage vessel,
a vent valve, and one controlled dewar.