APPLICATION NOTE NO. 64-1

Plumbing Installation -- SBE 43 DO Sensor and Pump on a CTD
September 2003

Application note in pdf format

This Application Note describes installation of an SBE 43 Dissolved Oxygen (DO) Sensor and pump (and associated plumbing) on an SBE 9plus CTD, using PN 90087 Universal Plumbing Kit. The plumbing guidelines for the SBE 9plus also apply to an SBE 19, 19plus, or 25 CTD, except as noted.

Sharp knife or scalpel for cutting tubing
Straight-edge ruler for measuring and cutting

Note for SBE 9plus or 25:
If your conductivity sensor does not have a conductivity tube support, install the conductivity tube support kit before installing the plumbing. (See Application Note 36 for installation details)

Conductivity tube support kit:
Part Number 50094 for aluminum sensors
Part Number 50108 for titanium sensors

Basic considerations for plumbing installation:

• Use the minimum tubing lengths necessary, but avoid tight bends in the tubing. Tight bends place stress on the tubing connections at the sensors, which can lead to failures at the connections.
• Do not create any vertical loops in the tubing. Loops trap air, preventing the pump from working properly.
• Secure each tubing connection with two cable ties.

Plumbing installation details differ, depending on whether the sensors will be deployed in a horizontal or vertical configuration. See Horizontal Configuration Schematic and Details and Vertical Configuration Schematic and Details below.

The horizontal configuration is most commonly used when the CTD is integrated with an SBE 32 Carousel Water Sampler with an extension stand. When installing plumbing for the horizontal configuration:

• Configure the system as follows:

• Place the DO sensor intake above the conductivity sensor exhaust.
• Place the pump intake above the DO sensor exhaust.
• Orient the pump with the exhaust outlet corner up.

Failure to configure the system in this manner can trap air, preventing the pump from working properly.

• Place a 13 mm (0.5 inch) piece of 9.5 mm ID Tygon tubing at the DO sensor intake and exhaust. Slide the larger diameter tubing (13 mm ID) over the smaller diameter tubing to provide tight seals.

If the system does not include a DO sensor, connect the tubing from the conductivity cell directly to the pump intake.

DO sensor intake and exhaust tubing detail:

Secure each tubing connection with two cable ties (not shown).

Vertical Configuration Schematic and Details

When installing plumbing for the vertical configuration:

• (For SBE 9plus only) Place the opening of the intake and exhaust on the same horizontal plane. Attach exhaust tubing from the pump to the cage, as shown in the schematic below. Failure to place the exhaust tubing properly can lead to acceleration of water in the plumbing, with resulting errors in conductivity data.
  Note: Exhaust tubing is usually omitted by Sea-Bird for an SBE 19, 19plus, or 25.
• Place the exhaust away from the intake, so that exhaust water is not pulled into the intake. If the exhaust is too close to the intake, it will cause errors in the temperature data, because the pump transfers heat to the exhaust water.
• Place a 13 mm (0.5 inch) piece of 9.5 mm ID Tygon tubing at the DO sensor intake and exhaust. Slide the larger diameter Tygon tubing (13 mm ID) over the smaller diameter tubing to provide tight seals.
• If the system does not include a DO sensor, connect the tubing from the conductivity cell directly to the Y-fitting.

Secure each tubing connection with two cable ties.

Note: Exhaust tubing is usually omitted by Sea-Bird for an SBE 19, 19plus, or 25.

Last modified: 06 Apr 2007

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