Teledyne 6750 - Total Organic Carbon analyzers User Manual

Page 30

Theory of Operation

Model 6750

Teledyne Analytical Instruments

requires no wall reflectivity and is completely resistant to corrosive
gases. The NDIR unit requires no optical chopper motor or mechanical
devices but utilizes a single flashing infrared source to optically “chop”
the infrared (IR) beam, which equally irradiates CO

/reference detectors.

Using a reference eliminates water vapor interference. The non-
reflective, corrosive resistant sample cell removes the requirement for
chemically removing acid gases prior to detection.

Automatic gain control (AGC) is employed during the

reference/sample cycle to compensate for such factors as IR source
deterioration, dirty optical windows, etc. When the AGC level reaches a
predetermined threshold, an optics alarm is activated. Malfunctions of
major NDIR components are detected and indicated as an alarm,
providing “fail-safe” operation. Signal detection is completely
synchronous and because of the differential ratioing technique, drift is
virtually eliminated.

All critical optics are protected by sapphire windows. The NDIR

optical bench can be easily disassembled and windows cleaned (rarely
ever required) and reassembled within fifteen (15) minutes, without
realignment or the use of any tools.

The benefit of this absolute measuring, dual line spectral

differential analytical technique, is that it provides simple, direct
measurement of all CO

contributing factors (including background) for

a true and accurate calibration, and precisely offsets these effects for
very accurate TOC determinations.

2.4.5 Electronic Signal Processing, Display and Control

A true, industrialized Microsoft Windows™-CE Computer offers

complete automatic control of the analyzer, including the following:

• Benchmark/Auto-Validation

• Auto-Calibration

• Auto-Cleaning

• On-Board Historical Data for up to one (1) year

• Paperless Chart Recorder

• Diagnostics

• Networking (RS-232C/485)