Campbell-scientific CS511 Dissolved Oxygen Probe Manuel d'utilisateur télécharger pdf (Page 33)

Appendix C. PT4-L Agitator

C.1 Description

The PT4 agitator is a reliable, robust agitator for use in conjunction with probes

subjected to bio-fouling in ponds and stagnant water conditions (flow <5 cm/s).

probes require a minimum water velocity across their membranes to function

properly. Therefore, to measure DO in stagnant water conditions, it is necessary

to move the water past the membrane to get accurate and reliable DO

measurements. In many instances, the water also has a high bio-loading and the

probes become fouled resulting in inaccurate DO measurements.

FIGURE C-1. Preventing Bio-fouling of a DO Sensor

The PT4 agitator overcomes these problems. The device is designed so that a

soft-bristle brush sweeps across the probe membrane or sensor tip. This sweeping

action of the brush provides the required water velocity as well as prevents the

membrane from becoming bio-fouled.

The optimum sweeping frequency depends on the design of the probe and type of

membrane used and water conditions. An ON-time of 0.25 s and OFF-time of 5 s

is suitable in most circumstances.

C-1

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Campbell-scientific CS511 Dissolved Oxygen Probe Manuel d'utilisateur Page 33