Choosing a High-Temperature Proximity Sensor: +120, +150 or +180 °C, and Low-Temperature Types

A standard inductive proximity sensor is usually rated for about −25 °C to +70 °C. Above that, the plastic sensing face softens, the PVC cable stiffens or melts, and the electronics drift until the switching point moves or the sensor fails. This guide shows how to decide which temperature rating you actually need, what changes between inductive and capacitive high-temperature sensors, and which details besides the rating decide whether the sensor survives.

Step 1 — Find the Temperature That Actually Reaches the Sensor

The rating of a proximity sensor refers to the ambient temperature at the sensor, not the temperature of the process or the target. A 250 °C part passing a sensor a few millimetres away heats the face by radiation and convection; the same part 30 mm away may barely affect it. Measure or estimate:

• the air temperature at the sensor position in the worst operating state (summer, full load, doors closed);
• radiant heat from hot targets, furnace walls, moulds or ovens facing the sensor;
• conducted heat through the mounting bracket;
• heat on the cable route, which is often hotter than the sensor itself;
• the lowest temperature during a cold start or in winter for outdoor machines.

Add a margin above the measured maximum. If the result is close to a rating limit, choose the next rating up or move the sensor away from the heat source; a heat shield or a longer bracket is often cheaper than a higher rating.

Step 2 — Match the Rating

The last part of each SEGMENsensor part number is the temperature code (T120, T150, T180, L30 or L40), so the rating is visible on the label and in the order.

Step 3 — Inductive or Capacitive?

The choice depends on the target first and the temperature second:

For fast or precise detection of metal parts, an inductive sensor is the better choice wherever its rating is enough. A capacitive sensor is the answer when the target is not metal or when the temperature exceeds +150 °C; set its sensitivity on the real target, because its switching point depends on the material. The differences are covered in more depth in inductive vs capacitive proximity sensors.

Step 4 — Allow for Temperature Drift of the Sensing Distance

The switching distance of every proximity sensor changes with temperature. IEC 60947-5-2 — Proximity switches ↗ allows the real operating distance Sr to lie within ±10 % of the rated distance Sn, and the usable distance Su within ±10 % of Sr over the permitted temperature and supply range. In practice: design the target to pass at no more than about 81 % of Sn (the assured operating distance), and a sensor that switches reliably at room temperature will still switch at the top of its rating.

For HT inductive sensors, the rated distance runs from 1 mm (M8 flush) to 25 mm (M30 non-flush). Non-flush models reach further but need free space around the face, which also keeps them further from hot surfaces.

Step 5 — Check the Sensing Face and the Cable

Temperature ratings only hold if every part of the sensor is built for them. SEGMENsensor HT models use a PTFE sensing face, and the cable is silicone or PTFE on the heat-rated models; the capacitive L models use an oil-resistant PUR cable for the cold. A standard PVC cable run through the same hot zone will fail before the sensor does, so check the whole cable route. The trade-offs between the cable materials are explained in PTFE vs silicone cable for high-temperature sensors.

Temperature ratings of insulating materials are determined by ageing tests; the method is set out in IEC 60216-1 — Electrical insulating materials, thermal endurance properties ↗. That is why a material has a continuous rating lower than its short-term limit.

Typical High- and Low-Temperature Applications

• Ovens, dryers and curing lines: position of carriers, doors and conveyors near the heating zone.
• Plastics and rubber: mould and platen positions on injection moulding and vulcanising presses.
• Metal processing and foundry: hot parts on transfer lines, where the sensor is shielded from direct radiation.
• Glass and ceramics: detection of hot non-metal products with capacitive T150 / T180 models.
• Cold stores and outdoor equipment: L30 and L40 models for freezer doors, conveyors and outdoor machines in winter.

What to Send for a Recommendation

Frequently Asked Questions

Related reading: High-temperature inductive proximity sensors · High-temperature capacitive proximity sensors · PTFE vs silicone cable · Inductive vs capacitive proximity sensors · Special-environment proximity sensors
Last updated: 28 September 2026. Specifications reflect the SEGMENsensor product pages at the date of publication; datasheets and dimension drawings are sent on request.