IP67 vs IP68 Sensors: Compare Depth, Time and Real Exposure

What is the difference between IP67 and IP68 sensors?

The first digit is the same: 6 means dust-tight. The difference is the water-protection claim represented by the second digit. IEC 60529 defines the IP classification for enclosures; it is not a general ranking of sensor quality.

The water test concerns protection against harmful ingress under its specified conditions. Avoid translating either rating into “absolutely waterproof in every situation.” Oil, detergent, salt water, repeated cleaning and operating temperature introduce separate questions.

IP68 is therefore a reason to inspect a product’s immersion specification—not a reason to skip that specification. For an installation with no immersion, a documented jet rating or chemical-compatibility statement may matter more.

How deep—and how long—can an IP68 sensor stay underwater?

There is no single answer for all IP68 sensors. Ask for both the test conditions and the permitted operating conditions: depth or pressure, duration, water temperature, assembly state and whether the sensor is approved to function while submerged.

A published test duration is not an unlimited service-life promise

A useful documentation example comes from Phoenix Contact’s ECS-B-122X169-L-UV-NV GY enclosure, order number 1050212. Its product page specifies IP68 at 2 m for 24 hours and makes protection dependent on the associated faceplate assembly. This is an enclosure example, not an IP rating for an xsz sensor product.

The lesson is how to read the qualifier. A 24-hour test is evidence for the stated test; by itself, it does not establish months of powered underwater service. For a permanently submerged installation, obtain an explicit operating-use statement and any maintenance or replacement limits.

You cannot trade depth for time without supporting evidence

Do not convert a 2 m / 24 h result into 1 m / 48 h or 4 m / 12 h. There is no general “depth × time” allowance. A lower depth does not automatically validate a longer exposure, and a shorter exposure does not automatically validate greater pressure.

Describe your installation using the highest water level relative to the sensor, the longest uninterrupted immersion and the expected number of cycles. Include a pressurized vessel or moving-water condition if present; a depth-only description may not capture that exposure.

For permanent underwater operation: request confirmation that the exact sensor, cable assembly and sensing function are suitable for that use. “IP68” without operating limits is incomplete selection information.

Does IP68 also cover pressure washing?

No. Immersion and water-jet exposure are different tests. IPX7 and IPX8 do not automatically include the IPX5 or IPX6 jet requirements. A product can carry several ratings because the manufacturer is declaring protection against different exposures.

For example, an IP66/IP68 marking addresses both powerful water jets and the stated immersion conditions. For hot, high-pressure cleaning, examine the relevant IP69 or IP69K claim, its governing standard and its test details. Do not treat a “K” suffix or a larger number as interchangeable wording.

Detergents and steam need their own suitability checks

A water rating alone does not establish compatibility with your cleaning chemical, concentration or contact time. Nor does a hot-water claim automatically approve every steam-cleaning process. Ask about the complete material set: housing, sensing window, seals, connector overmold and cable jacket.

For maintenance teams, record the nozzle type, working distance, water temperature, cleaning agent and cleaning frequency. If operators regularly clean closer or hotter than the approved procedure, the nameplate rating does not resolve that mismatch. A shield or revised mounting position may reduce direct exposure, but still needs validation for the actual cleaning process.

Does the rating cover the connector and cable?

Only to the extent stated for the assembled product. A housing rating is not automatically the rating of a sensor joined to any available cordset. Check the mating connector, seal, assembly instructions and the condition in which the rating applies.

A concrete sensor example is SICK’s WTB4SC-3P2262VB01, part number 1115584. Its datasheet lists several enclosure ratings and qualifies them with a correctly mounted IP69K connecting cable. That model-specific footnote is the kind of condition buyers should look for—not an instruction to use its cable or torque on another sensor.

What changes when the connector is unplugged?

Do not assume protection specified for a mated connection remains available with the plug removed. If a connection will be open during cleaning or maintenance, obtain the separate unmated rating or use the specified protective cap. Dirt, damaged seals and incomplete engagement also belong in the inspection procedure.

Is a prewired sensor automatically safer in water?

A fixed cable removes one detachable interface at the sensor, but it does not qualify an exposed cable end, field splice or damaged jacket. Conversely, a connector sensor can be appropriate when the exact mated assembly is documented for the application.

Choose the connection around access, replacement and exposure. Compare the practical maintenance trade-offs in the prewired versus connector sensor guide; then verify the environmental limits of the selected assembly.

Can a sealed sensor still give the wrong signal when wet?

Yes. Keeping harmful water out of the enclosure and detecting the target correctly are separate requirements. OMRON’s photoelectric-sensor guidance notes that droplets on an optical lens can cause false switching or reduce sensing distance. That can happen without water entering the housing.

Match the trial to the sensing task: test target present and target absent with the expected wet face, background and operating distance. Record missed targets, false detections and recovery after cleaning. A dry bench check cannot establish performance in the wet state.

Also distinguish water exposure from material durability. Cleaning chemicals and oils can attack susceptible seals, plastics or cable materials over time. An intact enclosure on the first day does not establish long-term compatibility. Obtain material-specific limits instead of assuming that all stainless steel sensor assemblies behave alike.

Conduct checks through a controlled procedure with the machine made safe. Do not improvise immersion of energized equipment. For underwater sensing, require explicit manufacturer approval for powered submerged use; an enclosure test alone is not that approval.

What should a supplier prove before you approve the sensor?

Compare the quotation, datasheet and supporting evidence as one package. The important question is not whether the supplier has an impressive report, but whether its conditions cover the assembly and use you are buying.

Keep the document request short and specific

1. Identify the delivered assembly. Record the sensor part number and suffix, connector or cordset part number, cable type and any cap or gland included in the protected configuration.
2. Capture the exact claim. Request the IP marking, applicable standard and edition, test depth or pressure, duration, temperature and assembly state. A certificate with no relevant scope does not answer these questions.
3. Separate test evidence from permitted use. Ask for the datasheet/manual and supporting report or report summary, plus confirmation of continuous or repeated immersion and powered operation where required.
4. Resolve the other exposures. List jet cleaning, chemicals, salt water, temperature cycling, cable movement and outdoor exposure when present. Ask for the relevant limits; do not assume the IP claim covers them.
5. Agree the acceptance check and change control. Define the wet-state detection requirement and installation inspection. Recheck coverage if the sensor suffix, seal, cable or connector changes.

Should you choose IP67 or IP68 for your application?

Consider IP67 for temporary immersion within the documented conditions. Confirm the actual connection and do not extend a short immersion claim into permanent service.

Consider IP68 for a defined submerged duty that the manufacturer supports. Specify depth, duration, operating state and the complete assembly. Different IP68 products can have different limits.

For washdown, select for washdown—not just immersion. Check the relevant jet or hot-water rating and the cleaning materials. If both flooding and cleaning occur, document both.

The right purchase is the sensor whose evidence matches the real exposure and whose detection remains reliable in that exposure. A higher final digit, on its own, cannot make that decision.