Modules (Condulets) - Teledyne 514 Instruction Manual

1.0 Introduction
The quantitative measurement of a compound using the 514 is based on
Beer's Law, which states that the intensity of a beam of monochromatic
radiation transmitted through a sample decreases exponentially as the con-
centration of the absorbing sample increases.
To approximate monochromatic radiation, a specific wavelength is
isolated by the use of the interference-type filters. The filters allow transmis-
sion of NIR over a narrow band pass region of the NIR spectra and com-
pletely block all other wavelengths. Proper selection of the measuring and
reference filter wavelengths allows the accurate isolation and measurement
of the component of interest.
The use of two filters allows cancellation of energy changes due to
turbidity, dirty sample cell windows, and aging of the source and electronic
components.
The center band pass of the measuring filter is selected to transmit
energy in a narrow region where the component of interest absorbs strongly
in comparison with background absorbance. The center band pass of the
reference filter is selected to transmit energy in a band pass region where the
background absorption of NIR energy is equivalent to that seen by the
measuring filter. The reference filter is also selected to be in a region where
the component of interest has minimal absorption of energy.
The optical beam is converted from steady state to pulsed energy by the
rotation of the filters in the optical path. The measuring and reference pulses
of radiation strike a detector which converts the pulses of radiation into
electrical pulses which are then amplified. Signal processing involves
converting the electrical signals to logarithmic signals, and then comparing
the measuring to the reference logarithmic signals in order to give a readout
representing the concentration of the component of interest in the sample.
1.2
Physical layout of the analyzer is shown in Figures 1-1 and 1-2. The
control module is usually located apart from the analysis unit in a control
room. The explosion-proof version has the control and analysis units
mounted in one weather-resistant NEMA-12 enclosure suitable for outdoor
installation.
The analysis section is designed for hazardous area installation. Hous-
ings are rated for use in Class I, Div. I, Group D hazardous environments.
1–2
Teledyne Analytical Instruments
A Business Unit of Teledyne Electronic Technologies

Modules (Condulets)