FLAME SENSOR

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Specifications are subjected to change without notice. No patent rights are granted to any of the circuits described herein. © 1997 Hamamatsu Photonics K. K.

Quick Detection of Flame from Distance,

Compact UV Sensor with High Sensitivity and Wide Directivity,

Suitable for Flame Detectors and Fire Alarms.

Hamamatsu R2868 is a UV TRON ultraviolet detector that makes

use of the photoelectric effect of metal and the gas multiplication

effect. It has a narrow spectral sensitivity of 185 to 260 nm, being

completely insensitive to visible light. Unlike semiconductor

detectors, it does not require optical visible-cut filters, thus

making it easy to use.

In spite of its small size, the R2868 has wide angular sensitivity

(directivity) and can reliably and quickly detect weak ultraviolet

radiations emitted from flame due to use of the metal plate

cathode (eg. it can detect the flame of a cigarette lighter at a

distance of more than 5 m.).

The R2868 is well suited for use in flame detectors and fire

alarms, and also in detection of invisible discharge phenomena

such as corona discharge of high-voltage transmission lines.

APPLICATIONS

q Flame detectors for gas/oil lighters and matches

q Fire alarms

q Combustion monitors for burners

q Inspection of ultraviolet leakage

q Detection of discharge

q Ultraviolet switching

GENERAL

Parameters

Rating

Units

Spectral Response

185 to 260

nm

Window Material

UV glass

—

Weight

Approx. 1.5

g

Dimensional Outline

See Fig. 3

—

MAXIMUM RATINGS

Parameters

Rating

Units

Supply Voltage

400

Vdc

30

mA

1mA

Operating Temperature

-20 to +60

°C

CHARACTERISTICS (at 25

Parameters

Rating

Units

Discharge Starting Voltage (with UV radiation)

280

Vdc Max.

Recommended Operating Voltage

325

±25

Vdc

Recommended Average Discharge Current

100

µA

10

cpm Max

5000

cpm Typ.

NOTES:

1) This is the maximum momentary current that can be handled if its full width

at half maximum is less than 10

µs.

2) If the tube is operated near this or higher, the service life is noticeably reduced.

Use the tube within the recommended current values.

3) Measured under room illuminations (approximately 500 lux) and recommended

operating conditions. Note that these values may increase if the following

environmental factors are present.

1. Mercury lamps, sterilization lamps, or halogen lamps are located nearby.

2. Direct or reflected sunlight is incident on the tube.

3. Electrical sparks such as welding sparks are present.

4. Radiation sources are present.

5. High electric field (including static field) generates across the tube.

4) These are representative values for a wavelength of 200 nm and a light input

ultraviolet radiation and the drive circuitry employed.

Figure 1: UV TRON’s Spectral Response and Various

Light Sources

TPT B0009EA

200

300

400

500

600

700

800

900

100

WAVELENGTH (nm)

100

50

0

UV TRON s

SPECTRAL

RESPONSE

SUNLIGHT

GAS

FLAME

TUNGSTEN

LIGHT

ULTRAVIOLET

VISIBLE

INFRARED