Beams

SRA-24 REFLECTIVE BEAM DETECTOR

SRA-24 REFLECTIVE BEAM DETECTOR

APPLICATION

Hochiki’s Reflective Beam Detector is designed for smoke detection in large spaces such as halls, warehouse, museums, theatres etc., where conventional point detection is impractical or more costly. The unit is not suitable for applications where strong or reflected sunlight is present, in these instances the SPB-24N should be considered. The unit detects smoke linearly over the protected range enabling early detection before the fire spreads. Compact design, good looks and flush mounting installation makes this unit ideal for fitting in areas where architectural considerations are important.

GENERAL DESCRIPTION

The Photoelectric reflective beam detector consists of the SRA-24 unit and a reflector, which face each other at a distance of between 25ft and 100ft. In the event of fire the smoke generated will decrease the amount of near infrared light energy on the SRA-24, this decrease is electronically interpreted to identify the occurrence of fire. An important feature of the detector is that it monitors the protected space linearly. This enables the detector to identify a fire before it spreads, even when the smoke is scattered over a large area. The fire detection sensitivity is factory set at 20% beam obscuration and it can be changed to 30% with
a sensitivity switch.

The status of the unit is indicated by three LEDs which are viewed through a unique lens that allows good visibility from any viewing angle, particularly from beneath the unit. The LEDs indicate, Normal, Setup, Fault and Fire Condition, so the user can verify which unit is in alarm. The unit indicates a fault on the zone under the following conditions:
• Compensation limit exceeded
• Total obscuration of beam
• Beam detector unit removed from zone

ENGINEERING SPECIFICATIONS

The contractor shall furnish and install, where indicated on the plans, HOCHIKI America SRA-24 Reflective Beam Detector. The detector shall have a range of 25 feet to 100 feet. The beam smoke detector shall be field adjustable to one of the two obscuration settings of 20%, or 30% per span. These settings shall be capable of being verified with calibrated filters. Side to side spacing shall be a maximum of 60 feet on center.

The reflective beam detector shall posses circuitry that automatically compensates for normal ambient changes in the intensity of the emitted beam strength. The microprocessor shall provide compensation for a change in received signal value, with time, caused by contamination of the optics. Since such a change with time appears as a slow change in the beam signal, the microcomputer compensates in such a manner that the signal moves closer to the reference data at a rate of approximately +1% per hour. When this compensating capability reaches a limit, the microcomputer automatically generates a trouble signal.

The reflective beam detector(s) shall also signal a trouble condition if the beam has a blockage of 90% for more than 20 seconds and automatically resets to normal when blockage is removed. The reflective beam detector(s) shall be UL listed for these applications. Voltage and RF transient protection shall be integral to the internal circuitry of the reflective beam detector so as to minimize false alarm potential.

To facilitate easy installation and setup, the reflective beam detectors shall employ signal strength indicating LED’s. Alignment shall be facilitated by turning an alignment adjustment screws and monitoring the relative signal strength based upon which LEDs are illuminated. The detectors shall also illuminate a red LED, which is visible externally, when an alarm condition is indicated. The reflective beam detector shall provide a Form “A” dry contact for alarm and Form “B” dry contact for trouble.

ENGINEERING SPECIFICATIONS

The contractor shall furnish and install, where indicated on the plans, HOCHIKI America SRA-24 Reflective Beam Detector. The detector shall have a range of 25 feet to 100 feet. The beam smoke detector shall be field adjustable to one of the two obscuration settings of 20%, or 30% per span. These settings shall be capable of being verified with calibrated filters. Side to side spacing shall be a maximum of 60 feet on center.

The reflective beam detector shall posses circuitry that automatically compensates for normal ambient changes in the intensity of the emitted beam strength. The microprocessor shall provide compensation for a change in received signal value, with time, caused by contamination of the optics. Since such a change with time appears as a slow change in the beam signal, the microcomputer compensates in such a manner that the signal moves closer to the reference data at a rate of approximately +1% per hour. When this compensating capability reaches a limit, the microcomputer automatically generates a trouble signal.

The reflective beam detector(s) shall also signal a trouble condition if the beam has a blockage of 90% for more than 20 seconds and automatically resets to normal when blockage is removed. The reflective beam detector(s) shall be UL listed for these applications. Voltage and RF transient protection shall be integral to the internal circuitry of the reflective beam detector so as to minimize false alarm potential.

To facilitate easy installation and setup, the reflective beam detectors shall employ signal strength indicating LED’s. Alignment shall be facilitated by turning an alignment adjustment screws and monitoring the relative signal strength based upon which LEDs are illuminated. The detectors shall also illuminate a red LED, which is visible externally, when an alarm condition is indicated. The reflective beam detector shall provide a Form “A” dry contact for alarm and Form “B” dry contact for trouble.


SPC-24 PROJECTED BEAM SMOKE DETECTOR

SPC-24 PROJECTED BEAM SMOKE DETECTOR

APPLICATION

The Hochiki America SPC- 24 Projected Beam Smoke Detector consists of an emitter and receiver. The projected beam smoke detector should be placed so that smoke generated by a fire will likely rise into the path of the beam. The receiver is constantly monitoring and measuring the intensity of the beam transmitted by the emitter. Should the smoke from a fire cause a decrease in the signal strength of a magnitude that exceeds the programmed obscuration setting, an alarm signal is generated.

The SPC-24 Projected Beam Smoke Detector can provide vital fire detection in applications where other types of detectors may not be able to respond quickly, or at all, to a fire condition. Examples of some applications where projected beam smoke detectors have been successfully used include:

•atriums
•gymnasiums
•theatres
•museums
•factories
•tunnels
•churches
•stables
•warehouses
•anechoic chambers
•high air velocity areas

The Hochiki America SPC-24 Projected Beam Smoke Detector may also be used in conjunction with more traditional spot type smoke detection devices to provide an even more comprehensive detection system.

OPERATION

The near infrared pulsed beam generated by the emitter is sensed by the photodiode of the receiver, where it is converted into an electrical signal. This signal is then amplified and applied, via an analog to digital converter, to a microprocessor. The normal state signal (the initial beam data) once stored in the microprocessor is used as reference for comparison with subsequent beam signals. When there is a difference between actual beam strength and stored reference data that exceeds the programmed alarm obscuration reference level, a fire signal is produced. A trouble signal is generated if the beam is more that 90% obstructed (as opposed to partially obscured by smoke).

The microprocessor also provides compensation for a change in received signal value, with time, caused by contamination of the optics. Since such a change with time appears as a slow change in the beam signal, the microprocessor compensates in such a manner that the signal moves closer to the reference data at a rate approximately +1% per hour. When this compensating capability reaches a limit, the SPC-24 automatically generates a trouble signal.

A calibrated test filter is available upon request to test and verify the sensitivity setting of the SPC-24 projected beam smoke detectors.

ENGINEERING SPECIFICATIONS

The contractor shall furnish and install, where indicated on the plans, Hochiki America SPC-24 Projected Beam Smoke Detector. The projected beam smoke detector shall have a range of 32.8 feet to 328 feet. The projected beam smoke detector shall be field adjustable to one of the three obscuration settings of 25%, 50% or 70% per span. These settings shall be capable of being verified with calibrated filters. Side to side spacing shall be a maximum of 60 feet on center.

The projected beam smoke detector shall possess circuitry that automatically compensates for normal ambient changes in the intensity of the emitted beam strength. The microprocessor shall provide compensation for a change in received signal value, with time, caused by contamination of the optics. Since such a change with time appears as a slow change in the beam signal, the microprocessor shall compensate in such a manner that the signal moves closer to the reference data at a rate of approximately +1% per hour. When this compensating capability reaches a limit, the microprocessor shall automatically generate a trouble signal.

The projected beam smoke detector(s) shall also signal a trouble condition if the beam has a blockage of 90% or more for more than 20 seconds and automatically resets to normal when blockage is removed. The projected beam smoke detector(s) shall be UL listed for these applications. Voltage and RF transient protection shall be integral to the internal circuitry of the projected beam smoke detector so as to minimize false alarm potential.

To facilitate easy installation and setup, the projected beam smoke detectors shall employ signal strength indicating LED’s. Alignment shall be facilitated by turning an alignment adjustment wheel and monitoring the relative signal strength based upon which LED’s are illuminated.

The detectors shall also illuminate a red LED, which is visible externally, when an alarm condition is indicated. The projected beam smoke detector shall provide a Form “A” dry contact for alarm and Form “B” dry contact for trouble.

STANDARD FEATURES

• Microprocessor based for reliability
• Simple setup & alignment with signal strength LED’s
• Provides 60 feet on center linear protection at a range of 32.8 feet to 328 feet
• Automatic compensation for signal drift or dirty lens
• Three field adjustable sensitivity settings
• Form A alarm and Form B trouble contacts
• Calibrated filters available to verify sensitivity
• Color-coded emitter and receiver labels for easy recognition