Sensor technology in high-temperature lighting systems works by continuously monitoring the thermal condition of the luminaire and reacting automatically based on that data, for example by dimming or protecting the system. The sensor detects temperature rises before they cause damage to the LED driver or light source. This is crucial in industrial environments where standard lighting simply succumbs to the heat. In this article, we answer the most frequently asked questions about this topic.
Which sensors are used in industrial lighting systems?
Industrial LED luminaires primarily use three types of sensors: NTC thermistors (negative temperature coefficient), PT100/PT1000 temperature sensors, and thermocouples. Each type has its own area of application, depending on the desired measuring range, required accuracy, and environmental conditions.
NTC thermistors are the most common choice in LED fixtures. They are inexpensive, compact, and respond quickly to temperature changes. They are typically placed on or close to the LED module or driver to accurately track the operating temperature.
PT100 and PT1000 sensors offer higher accuracy and are more stable over a wide temperature range. They are used when precision is essential, such as in luminaires operating in environments up to +120°C. Thermocouples are used less frequently in lighting fixtures, but are indispensable in the most extreme industrial applications.
In addition to temperature sensors, modern fixtures sometimes also contain motion sensors, light sensors (photodiodes), or humidity sensors. For High-temperature lighting however, the thermal sensor is always the core of the system.
How do high temperatures affect the operation of sensors in luminaires?
High ambient temperatures pose a direct threat to the reliability of sensors in LED luminaires. When a sensor operates outside its specified temperature range, measurement accuracy decreases, signals can become distorted, or the sensor can fail completely. This has direct consequences for the protection of the luminaire.
A practical example: an NTC thermistor designed for a maximum of 85°C will quickly go beyond its operating range in a steel mill or near a blast furnace. The resistance value then changes non-linearly, making the measurement unreliable. The driver responds to erroneous data and may fail to protect the LED module adequately or in time.
In addition, heat transfer plays a major role. In fixtures exposed to infrared radiation, such as in steel mills, the sensor can also heat up indirectly due to radiant heat, even if the ambient air is relatively cool. Proper fixture design takes this into account by thermally isolating the sensor from external heat sources and placing it as close as possible to the critical component.
What is the difference between passive and active thermal protection in LED luminaires?
Passive thermal protection relies on the design of the fixture itself to dissipate heat, without using sensors or electronic control. Active thermal protection uses sensors to measure temperature and automatically adjusts based on that, for example by dimming or temporarily turning off the fixture.
Passive protection: design as foundation
Passive protection involves material selection, cooling fins, thermally conductive connections, and the thermal mass of the fixture. A well-designed heatsink can dissipate a large portion of the heat without any electronics. This system is robust and maintenance-free, but offers no flexibility during unexpected temperature peaks.
Active protection: sensor-driven intelligence
Active protection adds an intelligent layer. The sensor continuously measures the temperature of the LED junction or the driver. As soon as a threshold is reached, the system responds automatically. This can be:
- Automatic dimming to reduce heat generation
- Sending a warning signal to a management system
- Temporarily switch off the luminaire to prevent overheating
- Return to full capacity as soon as the temperature drops
In the harshest industrial environments, such as steel mills or climate chambers, active protection is not a luxury but a necessity. Passive and active protection are almost always combined in practice for maximum reliability.
How does automatic dimming based on temperature sensors work?
Automatic dimming based on temperature sensors works via a feedback loop: the sensor measures the current temperature, compares it with a set threshold value, and controls the LED driver to reduce the power as soon as the temperature gets too high. This protects the light source without completely turning off the fixture.
The process typically proceeds in stages. Suppose a luminaire has a maximum junction temperature of 85°C. At 75°C, the driver automatically begins to dim, for example, to 80% of the rated power. If the temperature rises further, the driver dims further. If the temperature drops again, the system gradually returns to full brightness.
This principle is called “thermal fold-back.” The major advantage is that the lighting remains operational, even under extreme loads. In a 24/7 production environment, that is invaluable: a luminaire that protects itself without manual intervention keeps production running.
Modern drivers increasingly combine this function with DALI or other protocols, so that the dimming behavior can be monitored and configured remotely. That makes the luminaire part of a broader lighting control system.
What standards and certifications apply to sensors in high-temperature lighting?
For industrial LED fixtures operating in high-temperature environments, IP classifications and IK ratings are the most direct and relevant certifications. A high IP rating, such as IP66 or IP67, guarantees that the luminaire is protected against dust and water, which indirectly protects the sensor and electronics as well. The IK rating indicates how well the luminaire can withstand mechanical impacts.
For ATEX environments, where there is a risk of explosion due to gases or dust, additional requirements apply to all components in the luminaire, including the sensors. An ATEX-certified luminaire has sensors and wiring that meet strict requirements regarding sparking and thermal load.
Additionally, the temperature classification of the luminaire itself plays a role. Luminaires are tested for their maximum surface temperature, which is directly related to the thermal protection provided by the sensor technology. If in doubt about the correct classification for a specific application, it is advisable to have this assessed by a specialist.
When is a luminaire with integrated sensor technology the right choice?
A luminaire with integrated sensor technology is the right choice when the ambient temperature is variable or unpredictable, when the luminaire is difficult to access for maintenance, or when lighting failure has direct consequences for safety or production. In stable, temperate environments, passive protection may suffice.
Concrete situations where integrated sensor technology offers added value:
- Steel mills and foundries where temperatures fluctuate strongly and infrared radiation is a constant factor
- Climate chambers with an operating range of -45°C to +120°C, while the sensor also protects against excessively low temperatures
- Offshore and maritime environments where corrosion, moisture, and temperature fluctuations come together
- High installation heights where a luminaire must function for years without maintenance
- 24/7 operations where downtime directly means loss of production
In all these cases, the sensor is not only a safety component, but also an investment in continuity. A luminaire that protects itself extends its own lifespan and lowers total maintenance costs over the entire lifecycle.
Practical example: Tata Steel IJmuiden
At Tata Steel IJmuiden, JEL provided the lighting near the production process as part of a sustainability project. Close to the hot steel, temperatures rise to +120 °C, the steel emits infrared radiation and the air composition is aggressive. JEL supplied Snapper HT, Barracuda HT and Orca HT, chosen per location. Near the working area, 100 lux is achieved, with a uniformity of up to 0.55.
Infrared radiation is a separate design factor here. Heat that arrives as radiation warms the luminaire without the air temperature accounting for it. The HT versions reflect that radiation instead of absorbing it, so that the LED and the driver stay within their temperature window.
For sensor-based thermal protection, this means that measuring the ambient air can underestimate the actual load. The luminaire itself must be able to withstand the radiation; a sensor that measures at the right component is then a complement to a good thermal design, not a replacement for it.
Read more about the Tata Steel IJmuiden project
How JEL Products Uses Sensor Technology in High-Temperature Lighting
JEL Products assembles and supplies LED fixtures specifically developed for the most demanding industrial environments, including applications where sensor technology makes the difference between a reliable installation and a costly failure. The approach is always tailored to the customer’s specific circumstances, rather than relying on a one-size-fits-all solution.
Specifically, JEL Products provides support in the following areas:
- Technical advice on the correct sensor selection and position for the specific ambient temperature
- Luminaires with integrated thermal protection, suitable for temperatures up to +120°C with the HT line
- Lighting for the areas outside the ATEX zones, with referral to a certified Ex manufacturer for the zones themselves, and custom solutions for applications involving extreme corrosion or chemical exposure
- Lighting design including thermal analysis of the installation environment
- Engineering support from commissioning to maintenance
- ISO 9001 and VCA-certified working method for quality assurance in every project
Whether it concerns a steel plant, a climate chamber, or an offshore platform, the question is always the same: which lighting keeps going where other fixtures fail? Contact us via the JEL Products Contact Page to discuss the options for your specific situation.