CHEMOTRONIC III
9
The CHEMOTRONIC determines the cloud point of hard resins in solutions based on
mineral distillates of analytical quality. To determine the cloud point accurately and
reproducibly, the temperature of the test liquid must be cooled down under
reproducible conditions until a reduction of transparency due to the effect of
suspended particles, i. e. turbidity occurs. The cooling rate plays a dominant role in
these local saturation and precipitation processes. However, the transparency
reduction due to colour changes must be eliminated in turbidity measurements. The
observed effect of the liquid on light passing through it will change in case of colour
changes, but the turbidity will not change. Therefore infrared light is generally
chosen for turbidity measurements to reduce the absorption effect caused by
different colours. However, turbidity is not empirical. It depends on the effect of
suspended particles on infrared light passing through the liquid, which in turn
depends on the similarity of the process and the measurement each time.
As the turbidity measurement must be combined with the temperature
measurement, a special infrared-photocell-system has been designed for the
CHEMOTRONIC.
This fibreglass infrared-photocell-system measures the absorption of the infrared
light beam passing through the glass test tube. The spectral response of the silicon
photo diodes shows a max. sensitivity at approx. 950 nm, which is well beyond the
region of visible light (380 - 780 nm), so that effect of visible colour changes is
eliminated generally. This makes the photocell more sensitive for low turbidity
measurements.
The output signal of the photocell detection circuit decreases linear with increasing
turbidity within the relevant turbidity range. The user can adjust which turbidity
point is recognized as the cloud point by executing a calibration procedure and
choosing one of ten turbidity levels.
The fibreglass infrared-photocell-system for turbidity measurement in the
CHEMOTRONIC III has proven to be a rugged and reliable device, designed for
continuous use in factory environment, if the tips of the fibreglass are kept clean.
Summary of Contents for HEMOTRONIC III
Page 54: ...CHEMOTRONIC III 54 Appendix...
