Teledyne GFC 7001EM operation manual Segment Sensor, Schmidt Triggers

Theory of Operation Model GFC7001E Carbon Dioxide Analyzer

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 11-10: GFC Light Mask

M/R SENSOR

This emitter/detector assembly 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.

Measurement

Reference

Pulses

Pulses

IR Beam

Pulses

Segment Sensor

Pulses

MR Sensor

Pulses

Figure 11-11: Segment Sensor and M/R Sensor Output

SCHMIDT TRIGGERS

To ensure that the waveforms produced by the Segment Sensor and the M/R Sensor are properly shaped and clean, these signals are passed through a set of Schmidt Triggers circuits.

Teledyne Analytical Instruments 241