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SBE 27 pH/O.R.P (Redox) Sensor

SBE 27 pH/O.R.P (Redox) Sensor
The SBE 27 pH and O.R.P. (Redox) sensor combines a pressure-balanced, glass-electrode, Ag/AgCl reference probe and platinum O.R.P. electrode to provide in-situ measurements at depths to 1200 m. The replaceable pH probe is permanently sealed and is supplied with a soaker bottle attachment that prevents the reference electrode from drying out during storage. The sensor is a modular, self-contained package that is easy to install, service, and calibrate.

The SBE 27 is intended for use as an add-on auxiliary sensor for profiling CTDs (SBE 9plus; SBE 19, 19plus, and 19plus V2 SeaCAT; and SBE 25 and 25plus Sealogger). Power / signal interface cables and mounting hardware are available separately.
Family Model Housing Connector Endcap
27   1 – aluminum 1 – AG 1 – Straight
      2 – MCBH 2 – Right angle

Example: 27.111 is an SBE 27 with aluminum housing, AG connector, and straight endcap. See table below for description of each selection:


COMBINATION pH/ORP (Redox) SENSOR - Sensor for use in profiling mode only, 1200 meter depth capability. Includes plastic soaker bottle, KCl soaker solution. and complete documentation.

Replaceable pH probe is permanently sealed & is supplied with soaker bottle attachment that prevents reference electrode from drying out during storage. Soaker solution is pH 4 buffer solution saturated with KCL.

SBE 27 can be ordered in two ways:

  • By itself; consult Sea-Bird to order interface cable or mount kit separately, if needed.
  • As an option in SBE 9plus, 19plus V2, or 25plus Auxiliary Sensor Options, complete with sensor, CTD interface cable, & mount kit.

Sea-Bird does not recommend use of pH or pH/ORP sensor for moored applications; see Application Note 76: pH or pH/ORP Sensors and Moored Applications.

SBE 27 Connector Selections — MUST SELECT ONE
27.11x AG connector

Wet-pluggable connectors may be mated in wet conditions. Their pins do not need to be dried before mating. By design, water on connector pins is forced out as connector is mated. However, they must not be mated or un-mated while submerged. Wet-pluggable connectors have a non-conducting guide pin to assist pin alignment & require less force to mate, making them easier to mate reliably under dark or cold conditions, compared to XSG/AG connectors. Like XSG/AG connectors, wet-pluggables need proper lubrication & require care during use to avoid trapping water in sockets.

Note: SBE 27 uses 6-pin AG-306 or MCBH-6 connector; photos are for illustration of differences between XSG/AG and MCBH connectors.

27.12x Wet-pluggable (MCBH) connector
SBE 27 Endcap Selections — MUST SELECT ONE
27.1x1 Straight endcap (for vertical mounting) Photo at top shows straight endcap. SBE 27 must always be mounted with pH probe in an approximately vertical orientation, because bulb at bottom is filled with a KCl solution, and needs to stay filled while in use. Deviation from vertical by some degrees will not affect data, as long as bulb remains filled. Right angle probe configuration is typically required for applications where CTD is mounted horizontally (for example, in extension stand below SBE 32 Carousel Water Sampler) & SBE 27 is mounted to CTD.
27.1x2 Right angle endcap (for horizontal mounting)
SBE 27 Spares & Accessories
17898 Interface cable, SBE 27 to 9plus, AG/RMG connectors, 0.8 m (DN 31749) These are cables to interface SBE 27 to Sea-Bird CTDs. Order cable to match CTD and to match connector type.
171825 Interface cable, SBE 27 to 9plus, wet-pluggable connectors, 0.8 m (DN 32844)
171704 Interface cable, SBE 27 to 19plus / 19plus V2 / 25 / 25plus, AG/RMG connectors, 1.1 m (DN 31749)
171826 Interface cable, SBE 27 to 19plus / 19plus V2 / 25 / 25plus, Wet-pluggable connectors, 1.1 m (DN 32844)
30459 Plastic soaker bottle for pH probe Soaker bottle filled with soaker solution comes with SBE 27; this is spare.
50020 pH sensor O-ring kit Spares kit includes 1 each of:
  • 231004 Backup ring for LS021 L-seal (end cap to housing seal)
  • 30072 O-ring, Parker 2-017 N674-70 (XSG connector seal)
  • 30097 O-ring, Parker 2-111 N674-70 (sensor to end cap seal)
  • 30806 L-seal, LS021 (end cap to housing seal)
24023P pH electrode (prepped for installation, document 67072) Electrode & electrode guard come with SBE 27; these are spares.
23190C pH electrode guard
25001 KCl soaker solution, 500 ml bottle Soaker solution is pH 4 buffer solution saturated with KCL. When SBE 27 is not in use, place plastic soaker bottle over pH electrode to prevent loss of internal electrolyte & resulting change in sensor performance. Soaker bottle filled with soaker solution comes with SBE 27; this is spare solution.
23041 Zinc anode ring Spare anode.