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The S509 is a "two color" flame monitor that employs both a Si (silicon) and PbS (lead sulfide) photo detector. The Si element is a "see through" element which is in front of the PbS element. The Si element acts as a detector as well as a filter for the PbS element. Using these two elements results a very wide spectral range, from 350-3000 nm (nanometers).

The signal from the two detectors are amplified separately then combined into one signal which is transmitted to the signal processor. The signal from these detectors is a flicker signal. All flames pulsate creating a flicker component which is what the S509 detects. The flicker frequencies emitted from flames range 0-2000Hz. The S509 responds to only the higher frequencies while rejecting the lower frequencies which are part of the general furnace or background flames.

The Si element responds to only incandescent or visible (to the naked eye) flames and will not pick up luminescent flame such as natural gas. The PbS element, on the other hand, will respond to all types of flames including natural gas. For this reason, if one is using the S509 for natural gas it is recommended that Si channel be turned off. This can easily be done by turning the Si pot (potentiometer) on the viewing head full counter-clockwise.

The Si element is a photodiode that is operated in the photovoltaic mode. (The diode generates current when exposed to light or radiation). The sensitivity range of this element is quite large so some means to prevent saturation in the first stage of amplification is required. (The PbS element has a rather limited dynamic range exhibiting not more than 15:1 ratio from dark to a bright signal). In order to prevent saturation an AGC (automatic gain control) circuit is used so that the DC component or "brightness" signal doesn't saturate causing a loss of the AC component or flicker signal.

The S509 employs electronics self-checking which is implemented by using an electronic switch that disconnects the photo detectors every second for 200 milliseconds. The resulting chopped signal is fed to the signal processor which monitors the signal in a fail-safe manner.

Please call or email for pricing and availability at 281-421-1321 or sales@pco2.com.

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