Watchdog Liquid Nitrogen Level Sensor, Monitor, Alarm & Control

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See the Manual for the Watchdog

Watchdog Description

The Watchdog is a user configurable, thermistor based level sensor for liquid nitrogen monitoring and control applications. It is equipped with a bi-color LED that tells the state of the sensor (Red - Sensor Warm Out of the LN2, Blue - Sensor Cold In the LN2). The Watchdog continuously monitors the sensor and will alarm if there is a sensor failure. It has separate relay outputs for control and alarm functions. It is externally configured for use via a Red or Blue DB-9 plug. When the Watchdog LED is the same color as the plug everything is normal, when the colors are opposite it activates the output. It can be configured as a stand-alone High-level (Red plug) or Low-level (Blue plug) monitor with local or remote alarm function. It can be used to control an overfill shutoff valve or low-level fill valve. Two Watchdogs can be ganged together to function as a basic liquid level controller. Although the Watchdog is powered by a 24 vdc circuit it can switch externally supplied AC or DC power as well. In addition to the numerous built in functions and capabilities external circuitry can be added for timed control, alarm latching and similar functions.

Features:

• Tri-State Control Output
• Separate Alarm Output
• Visual Sensor State Indicator
• Continuous Sensor Diagnostics
• 3 A Power Switching, Internally or Externally Supplied
• Low Heat Input to Dewar
• Small Footprint
• Low Cost

Watchdog

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Program Plug

The Program Plug is used to configure the Watchdog functions. It does this by interconnecting the 9 input and output pins on the Watchdog's DB-9 plug. The Program Plug also serves as an internally fused junction box for the output wires and audible alarm. Factory supplied Program Plugs are color coded to the normal state of the LED.

Program Plugs

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Watchdog Packages

In addition to your ability to individually specify every feature and function, the Watchdog is also available in Standardized Packages. These stand-alone setups are combine a Watchdog, Program Plug and Power Supply into a complete, ready to go package.

Low Level Alarm Package (WD8-BA12-S1)

Part Number	Description	Features
WD8-BA12-S.25	Stand Alone Low Level Alarm	Local Audible and Visual Alarms when Liquid Nitrogen Level Falls Below the Sensor
WD8-RA12-S.25	Stand Alone Overfill Alarm	Local Audible and Visual Alarms when Liquid Nitrogen Level Reaches the Sensor
WD8-BP1NC23-S1	Low Level Tank Switcher	Supplies 24 vdc Control Power to an External (User Supplied) Supply Switching Valve when Liquid Nitrogen Falls Below the Sensor, NC Remote Alarm Contacts Open on Power or Sensor Failure, Local Visual Alarm, 1 amp Supply
WD8-RP2NC23-S1	Overfill Flow Cutoff	Supplies 24 vdc Control Power to an External (User Supplied) Supply Shut Off Valve when Liquid Nitrogen Reaches the Sensor, NC Remote Alarm Contacts Open on Power or Sensor Failure, Local Visual Alarm, 1 amp Supply
WD8-LL-S1	24 Volt Liquid Level Controller	Maintains Liquid Level Between Upper and Lower Sensors via an External (User Supplied) 24 vdc Soleniod Valve, Failsafe Control on Either Sensor Failure, Local Visual Sensor Failure Alarm, 1 amp Supply

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Accessories

Accessories

[Under Construction]

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