Sentry Classic Controller

Sierra Monitor’s Sentry Classic Controller provides a comprehensive plant-wide gas risk management system for monitoring combustible gas, Oxygen deficiency, and toxic gases to maintain safety in a plant.

The Sentry Classic Controller is a microprocessor-based system that includes management of the sensor modules, management alarm relays, interface with the user via the front panel display, printer output, Modbus digital communication, alarm indicators, and relay outputs.

The controller has a user-friendly front panel that includes a large display of the gas concentration and sensor numbers. A series of alarm LEDs instantly inform the user of alarm status on any of the eight sensors interfaced to the controller. These LEDs are solid for low alarm and flashing for high alarm. The keypad, together with the user-friendly menu on the alphanumeric display, can guide the user through setup, calibration, and maintenance of the Sentry system.

An internal self-diagnostic feature makes over 120 routine checks of operating parameters to ensure the system is performing properly. During calibration, the controller performs a dynamic range check on all connected sensors to ensure its resolution is sufficient to give an accurate reading. In addition, reports can be printed via an optional forty-column printer. A variety of reports are available, including status, system, key event, history, calibration, and diagnostic reports.

The Sentry Classic Controller is approved and certified by a variety of third party agencies, including FM and CE. These approvals and certifications assure our customers that we carry only the highest quality of products and performance.

Sentry Classic Controller

  • Menu Prompting – Guide and prompt users through system configuration and operation
  • System Security – Prevent unauthorized users from changing the configuration and identify those who have made changes via user identification codes
  • Diagnostics – Perform routine checks of operating parameters and alert users if a condition requires attention
  • Sensor Scan Display – Continuously view current sensor gas exposure readings
  • Multiplex Digital Signals – Reduce installation costs by multiplexing sensors to the controller on a common cable
  • Record-Keeping – Easily keep reports for history, key events, or calibration actions
  • Relay Logic – Customize relay responses for personalization preferences
  • System Flexibility – Expand the controller user experience with accessories, product add-ons, and enhancement packages

Specifications for Sentry Classic Controller

Power (Standard)

  • 120 VAC + 10-15%, 60 Hz
  • 12 VDC Nom; 10 to 29 VDC

Power (Optional)

  • 220 VAC + 10-15%, 50 Hz
  • 12 VDC Nom; 10 to 29 VDC

Power Consumption

  • 48-Watts nominal

Number of Channels

  • 2, 4, or 8


  • Operating: 32 o to 122oF (0o to 50oC)
  • Storage: -40 o to 131oF (-40o to 55oC)


  • 10% to 95% RH Non-Condensing


  • Standard: 3 DPDT 3A, 115 VAC
  • Ind. Relay Option: 16 SPDT 6A, 115 VAC
  • Custom Relay Option: 16 SPDT 6A, 115 VAC
  • Output Expansion: 16 SPDT 6A, 115 VAC

Analog Outputs

  • 4-20 mA Current Source
  • Loop Resistance 800 ohms max.


  • 4 digit ½” LCD
  • 32 character (2 x 16) alphanumeric LCD

RS-232 Port

  • Standard Printer
  • Option MODBUS


  • Rack Mounted: 7.0 x 4.5 x 12.0 in. (17.5 x 11.2 x 30.0 cm)
  • NEMA 4X Enclosure: 17.5 x 16.2 x 6.3 in. (44.5 x 41.1 x 16.0 cm)
  • NEMA 7 Enclosure: 22.0 x 21.5 x 14.0 in. (55.9 x 54.6 x 35.6 cm)


  • Rack Mounted: 7 lb. (3.2 Kg)
  • NEMA 4X Enclosure: 25 lb. (11.3 Kg)
  • NEMA 7 Enclosure: 143 lb. (65.0 Kg)


  • FM Approved
  • CE Mark


  • Rack Mounting: Shelf for insertion in Instrument Cabinet
  • Panel Mounted: Panel bracket, bezel
  • NEMA 4X Enclosure: Wall or vertical surface
  • NEMA 7 Enclosure: Explosion Proof, Class 1, Div I, Groups C & D

How to Purchase the Sentry Classic Controller

Find Your Local Sales Partner

We work with a variety of sales partners around the world to increase our ability to reach customers. If you are looking to purchase the Sentry Classic Controller, please contact the sales partner that covers your location:

Contact Us

You can directly contact us to receive a quote: