Service manual

Section - VI Reading Station BT3000 PLUS Rev. 0, Soft Ver. 8 Page 3 of 12
The reference channel provides stability to the transmission signal when the
photometric system is used in the monochromatic mode. When the photometer is
selected in the bichromatic mode e.g. 340/700nm, the reference channel is not
utilized as the same function is accomplished by the 700nm channel.
The Light path
The photometer lamp transmits light beam, which converges on the center of
reading cuvette, and then through the cuvette it is reflected into the photometer
module by the 90º quartz prism located inside the cuvette drum (see Figure 6-1).
A small quantity (approximately 2%) of light flux is captured by the reference
photodiode prior to the light passes through the cuvette.
6-2.1. REACTION CUVETTE OPERATING PRINCIPLE
The light is transmitted through the light cone, into the reaction cuvette, and then
reflected into the photometer module by the quartz prism located inside the
cuvette system housing. The UV specific optical glass transparent cuvettes allow
transmission of wavelengths down to 340nm. The function of the photometer
module is to monitor and measure the color variations or absorbance values,
between different reaction mixtures over a wavelength range from 340nm-700nm.
After a reaction cuvette has passed a photometer measuring position and the
reaction mixture has been analyzed, the cuvette moves on towards the washer
module where the single piston drains, rinses, and dries the reaction cuvette for
re-use.
6-2.2. LIGHT SOURCE
The photometer light source consists of a 12 Volt, 35 Watt tungsten halogen lamp
with integral dichroic reflector for the dissipation of infrareds. The lamp is secured
through the lamp retaining spring clips on the light cone for easy removal or
substitution (see Figure 6-1). This custom made, UV enhanced, halogen lamp
provides a high radiation output in the 340nm UV range throughout its operating
life of approximately 2000 hours.