The fluctuating component of the signal from a photodetector monitoring transmitted light through a suspension can be used to access the size of the particles since larger particles will cause a larger fluctuation in sensor output. The Photometric Dispersion Analyser (PDA2000) produced by Rank Brothers Ltd can be used analyze the extent of flocculation of suspensions. For typical flow rates the AC component of the signal is monitored at 20-500Hz (see Photometric Dispersion Analyser PDA2000 Operating Manual). The PDA2000 uses a small diameter tube of either 1 or 3 mm for the flow path and a narrow light beam and hence the instrument has a small sample volume.
The HF Scientific turibidimeter has a sample cell that is approximately 2.5 cm in diameter. The diameter of the light beam is unknown, but the illuminated sample volume is certainly much larger than the PDA2000. The larger sample volume will cause the magnitude of the fluctuations relative to the dc signal to be smaller. However, the PDA2000 is not able to measure the large flocs that we create.
An example of research using the PDA2000 is Evaluation of floc strength by morphological analysis and PDA online monitoring.
1 Comment
user-e958e
Monroe,
This is pretty interesting. We should talk about this during our meeting with Len and the group tomorrow (Friday)