check
check
check
check
check
check
A hot-metal detector senses the infrared radiation that a hot target itself emits — its sensing element responds to radiant heat, so it detects hot metal regardless of ambient lighting, and it is used to identify the leading edge and direction of moving hot material on rolling and continuous-casting lines. A cold-metal detector senses light reflected from a workpiece that is not hot enough to emit strongly: it uses a visible-red or infrared light source with retro-reflective, through-beam or diffuse configurations to determine whether a cold workpiece has reached a position, typically on cooling beds, discharge points and conveyor lines. KJT Sensors supplies both families, plus a combined hot/cold-metal detector category for lines that must detect workpieces at both temperature stages. Sensing distance, response time and output type must be confirmed for the specific model.
The physical difference is the signal source: hot-metal detectors read radiation emitted by the target; cold-metal detectors read light reflected from the target. Target temperature is therefore the primary selection variable.
KJT Sensors' hot-metal detector combines a thermopile sensing element with germanium-lens imaging, plus photoelectric conversion, switching-comparison output and electronic compensation circuits (manufacturer-stated).
KJT Sensors' cold-metal detector offers visible-red or infrared light sources in retro-reflective, through-beam and diffuse configurations, delivering a switching output for in-position detection (manufacturer-stated).
A combined hot/cold-metal detector category exists for lines that track workpieces through both temperature stages; its specifications are confirmed per model.
Neither device's sensing distance, response time or output should be specified from category pages — steel-line selection always requires process, target-temperature and mounting details.
Every object above absolute zero emits infrared radiation, and the hotter the target, the stronger the emission. A hot-metal detector is built around this: KJT Sensors' hot-metal detector is a photoelectric detection device that combines a thermopile sensing element with germanium-lens imaging, with circuitry for photoelectric conversion, electronic switching-comparison output and electronic compensation (manufacturer-stated, Hot Metal Detectors).
Because the signal comes from the target itself, the detector does not need an external light source, and detection depends on the target being hot enough to stand out thermally from the background. This is why hot-metal detection is used for hot-rolling lines, hot-metal presence and position detection, billet or steel movement-direction detection, and continuous-casting and rolling automation (manufacturer-stated).
The same physics defines the failure modes: a target that has cooled below the detectable temperature contrast, a hot background (furnace glow, adjacent hot material) that raises the background level, or scale and dust in the optical path can each degrade detection. These are process-configuration questions, which is why the manufacturer confirms sensing distance, response time, output type, applied temperature and mounting method for the specific model.
A cold workpiece — below the temperature where emitted radiation dominates — is detected like an ordinary object: by light reflected from its surface. KJT Sensors' cold-metal detector determines whether a moving workpiece has reached the required position and supplies a discrete control signal for automation. Light-source options are visible red and infrared; detection configurations are retro-reflective, through-beam and diffuse-reflective (manufacturer-stated, Cold Metal Detectors).
Typical applications are in-position detection on cooling beds, at discharge points and on conveyor lines requiring reliable presence detection of cold metal (manufacturer-stated). Here the failure modes are the familiar photoelectric ones: target surface finish and reflectivity, ambient light, contamination on optics, and alignment — not target temperature.
