User Manual

For Liquid Nitrogen
Refrigerators
TW-307 B
LOW LEVEL
ALARM
Safety
The Cryo-Sentry is an optional accessory for se-
lected models of portable liquid nitrogen refrigera-
tors. It is designed to provide visual and audible
alarms when the liquid nitrogen level drops below a
preset level, usuaully 25 percent of the container
capacity. This monitoring system provides a high
level of security, alerting the user to low nitrogen
levels, and serves as a reminder for scheduled
refilling.
The Cryo-Sentry consists of three components: Alarm
Module, Power Supply, and Sensorcore.
Before using this accessory, read the Handle with Care
booklet (TW-10) provided with the unit. It details safety
precautions that must be read and understood before
using the equipment.
Following are a few precautions described in Handle
with Care. Please be sure to read the entire booklet.
Do not touch liquid or cold metal surfaces with
your bare skin. The liquid nitrogen used in cryogenic
refrigerators is extremely cold: -320°F (-196°C).
Exposure of skin or eyes to liquid, cold gas, or frosted
parts could result in a severe, frostbite-like injury.
Use only the sensorcore provided with this acces-
sory or the one originally shipped with the refrig-
erator. A tight-fitting plug or stopper will cause a
pressure increase in the container that may damage
the container and/or cause personal injury.
The Cryo-Storage low level alert arrives ready for
immediate use.
110 VAC Power
The alarm runs on either 110 VAC or 4 AA size battery
power. For 110 VAC, simply plug the wall transformer
into alarm module at the jack labeled “AC POWER”.
Next, plug the sensorcore into the alarm module at the
jack labeled “SENSOR”. (The Cryo-Sentry can either
be attached to your dewar with the VELCRO® strips
provided or can be mounted to the wall.) Lower the
sensorcore into the refrigerator, and plug the trans-
former into a 110 VAC outlet or a surge protected
power supply.
Battery Power
The alarm can also run on four (4) AA batteries. Once
installed, the batteries will supply power to the monitor
for an extended period of time.
To install the batteries, remove the back cover and
insert the batteries. The positive (+) terminal should be
pointed towards the “+” label on the battery holder.
Installation