DEPTHLINK / ENGINEERING GUIDE

Specify the position.
Then select the switch.

A practical guide to subsea proximity switches, underwater position switches and submersible end-of-travel sensing.

Start with the function, not just the name.

“Subsea proximity switch”, “underwater proximity switch” and “submersible position sensor” can describe closely related requirements. The wording alone does not establish the sensing technology, electrical output, immersion capability or suitability for your installation.

Define the position to detect and the input your control system expects. A discrete switch confirms a state; it does not necessarily measure continuous travel or distance. Specify continuous measurement separately if that is required.

Proximity sensing and limit switching

A proximity switch detects a suitable target without mechanical contact. A limit-switch requirement often describes detection at the end of movement, such as a valve reaching its open position. Some limit switches use physical actuation; other installations use non-contact sensing for the same end-position duty.

For a DepthLink enquiry, describe the target, travel and switching requirement. Confirm the actual sensing principle and electrical behaviour against the selected product’s approved specification.

Continuous submersion is an operating condition.

Underwater service can involve freshwater, seawater or process water, with different pressures, temperatures, chemicals and maintenance conditions. A generic waterproof description does not define a continuous-immersion duty. Include operating depth or pressure, exposure duration, temperature range and the media in your specification.

Five decisions to resolve together

1. The position and target

Which state matters: open, closed, latched, deployed or end of travel? Include target material, approach direction, available sensing gap and alignment tolerances.

2. The mechanical interface

Define the mounting thread, housing envelope, cable exit and protection from impact. Include drawings showing the switch and target through the mechanism’s movement.

3. The electrical duty

Identify the control input, switching voltage and current, contact or output requirements and required fail-state behaviour. Do not infer compatibility from the connector alone.

4. The complete cable assembly

Define connector part numbers, pin assignment, cable length and routing, conductor arrangement, jacket and termination. Review moving sections and strain relief with the sensing point.

5. Verification and documentation

Agree the configuration drawing, applicable tests and acceptance requirements. Where a safety-related function is involved, define the system requirements and required evidence explicitly.

Match the switch to its application.

Each application page covers the sensing duty, connection requirements and engineering questions for that environment.

Explore the complete system ↗

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Selecting an underwater position switch

Choose a sensing principle around the movement, target and electrical interface, then specify the complete subsea connection.

Start with the required signal

Decide whether the controller needs a discrete indication at one or more positions, or a proportional signal across a stroke. An end-position contact cannot describe the intermediate travel of an actuator. Record which machine state each signal must represent, including loss of power and a disconnected cable.

Match the sensing principle to the mechanism

For a magnetic proximity arrangement, define the magnet and its approach to the sensing face. For a mechanical limit arrangement, define the moving striker, operating travel and available overtravel. Avoid selecting on the word “underwater” alone: the mounting envelope, target arrangement and electrical duty are configuration-specific.

Information to include in your enquiry

Use the following checklist to capture the configuration. Where a value or drawing is not available, identify it as an open requirement for the engineering review.

Information to include in your enquiry
Requirement	What to record
Movement	Linear, rotary or latch motion; switching positions and tolerances
Target	Material, magnet reference, mounting and approach direction
Contact duty	Controller input, voltage, current and switching load
Environment	Continuous immersion, pressure, temperature, water chemistry

Confirm the complete configuration

Confirm the final part and assembly numbers, documentation revision and agreed acceptance requirements with the quotation. Product imagery is useful for identifying the concept; approved drawings and configuration-specific records define the supplied assembly.

Three feedback needs, three selection routes

Start with the question your controller must answer. An underwater proximity switch confirms a defined position; a mechanical limit switch confirms physical actuation; a linear position sensor follows travel. Selecting the output first avoids choosing a product solely by its housing size.

Three feedback needs, three selection routes
Controller needs to know	Starting point	Installation information
Is it open, closed, home or engaged?	Magnetic proximity switch	Target, approach direction, operating gap and contact state
Has a cam or striker reached this point?	Mechanical limit switch	Striker geometry, operating travel and separate end stop
Where is it within the stroke?	Linear position sensor	Measuring stroke, resolution, output and moving magnet mounting

Specification questions

What should I provide to start an engineering review?

Send the application and movement description, environmental conditions, control-system interface and any existing drawings or part references. Include the required cable route and the points that still need to be resolved.

What is the difference between a subsea proximity switch and an underwater proximity switch?

The terms often describe the same intended environment, but neither defines a numerical working limit. Compare the actual pressure, immersion, temperature, target, electrical and connector specifications for the supplied configuration.