Teledyne gfc 7000ta operation manual GFC Light Mask Sensor, Segment Sensor

Theory of Operation Model GFC7000TA Carbon Dioxide Analyzer

9.3.3.3. GFC Wheel

A synchronous AC motor turns the GFC wheel motor. For analyzers operating on 60Hz line power this motor turns at 1800 rpm. For those operating on 50Hz line power the spin rate is 1500 rpm. The actual spin rate is unimportant within a large rate since a phase lock loop circuit is used to generate timing pulses for signal processing.

In order to accurately interpret the fluctuations of the IR beam after it has passed through the sample gas, the GFC wheel several other timing signals are produced by other photo emitters/detectors. These devices consist of a combination LED and detector mounted so that the light emitted by the LED shines through the same mask on the GFC wheel that chops the IR beam.

KEY:

Detection Beam shining through MEASUREMENT side of GFC Wheel

Detection Beam shining through REFERENCE side of GFC Wheel

IR Detection Ring

Segment Sensor Ring

M/R Sensor Ring

Figure 9-11: GFC Light Mask

M/R Sensor

This emitter/detector assembly that produces a signal that shines through a portion of the mask that allows light to pass for half of a full revolution of the wheel. The resulting light signal tells the analyzer whether the IR beam is shining through the measurement or the reference side of the GFC wheel.

Segment Sensor

Light from this emitter/detector pair shines through a portion of the mask that is divided into the same number of segments as the IR detector ring. It is used by the synchronous / demodulation circuitry of the analyzer to latch onto the most stable part of each measurement and reference IR pulse.

Teledyne Analytical Instruments 201