American Magnetics 135 & 136 Liquid Helium Level Instruments (CE-Marked) - Manual (Page 29)

Rev. 3 17
Operation
Normal Operational Mode
a. When the measured liquid level exceeds the HI setpoint, the HI
LEVEL LED on the front panel is energized and a set of relay
contacts are closed on the 9-pin D connector J2 on the rear
panel (see the Appendix for the pinout). When the level reaches
or falls below the HI setpoint, the LED is extinguished and the
relay contacts open.
b. When the measured liquid level falls below the LO setpoint, the
LO LEVEL LED on the front panel is energized and a set of
relay contacts are closed on the 9-pin D connector J2 on the rear
panel (see the Appendix for the pinout). When the level reaches
or exceeds the LO setpoint, the LED is extinguished and the
contacts open.
Note
The HI and LO contacts are both closed on power-off of the
instrument which is a state unique to the power-off condition.
Note
If the LENGTH is adjusted subsequent to configuring the various
setpoints, the percentage of active length will be maintained for all
setpoints. For example, if the LENGTH is set to 100 cm and the HI
SETPOINT is set to 80 cm, then adjusting the LENGTH to 150 cm
will result in the HI SETPOINT being automatically scaled to 120
cm—i.e. the setting of 80% of active length is maintained.
3.2.4 Configure the A SETPOINT and the B SETPOINT
To adjust the A and B setpoints which specify the upper and lower limits
for the liquid level control band, place the control mode rotary switch in
the A SETPOINT position or the B SETPOINT position, respectively. Use
the RAISE/LOWER toggle switch to adjust the respective setpoint in the
same manner as described for the LENGTH adjustment in paragraph
3.2.2. The A and B setpoint adjustments are compatible with all three
units modes.
a. When the measured liquid level reaches or exceeds the A
setpoint, the A LEVEL LED on the front panel is energized.
When the level falls below the A setpoint, the LED is
extinguished.
b. When the measured liquid level falls below the B setpoint, the B
LEVEL LED on the front panel is energized. When the level
reaches or exceeds the B setpoint, the LED is extinguished.
0RGHO