wtw Turb 550, Operating Manual

Page: 19 / 54

Operation
19
4.1.2 Venting the sample
Air bubbles in the sample affect the measuring result to a
massive extent because they have a large scattering effect
on the incident light. Larger air bubbles cause sudden
changes in the measured values whereas smaller air bub-
bles are recorded by the instrument as turbidity. Therefore,
avoid or remove air bubbles:
Avoiding or remov-
ing air bubbles
l
During sampling, ensure all movement is kept to a mini-
mum
l If necessary, vent the sample (ultrasonic baths, heating or
adding a surface-active substance to reduce the surface
tension)
l
Use a flow-through vessel.