Radiometric Component
Non contact infrared measurement relies on a thin membrane containing a series of connected thermocouples. A micromachined thermopile converts incoming radiant energy into a small electrical voltage through the Seebeck effect. This component operates without an external power source for the sensing element itself.
Structural Layout
Silicon etching creates a suspended structure with low thermal mass and high isolation. The active area of a micromachined thermopile sits on this bridge to maximize the temperature difference between the hot and cold junctions. Gold or aluminum traces form the electrical path across the membrane.
This geometry allows the device to respond to infrared radiation in milliseconds.
Sensitivity Factor
Performance depends on the number of thermocouple pairs and the absorption efficiency of the surface coating. A micromachined thermopile typically produces a signal in the range of microvolts per degree of target temperature. Signal to noise ratios improve when the design minimizes the internal resistance of the junction chain.
The absorption layer must be uniform to ensure consistent results across the entire spectral range.
Integration Requirement
Signal conditioning electronics must reside close to the sensing element to prevent interference. Because a micromachined thermopile is sensitive to the temperature of its own housing, an internal thermistor provides a reference for cold junction compensation. This combined data allows the system to calculate the absolute temperature of a distant object.
The hermetic package often contains a silicon filter window to select specific wavelengths. Thermal stability of the mounting bracket prevents offset errors caused by heat soak from nearby motors or power supplies.
