Thermopile Detector / Radiometer
Temperature Sensor Module

Detectors that measure radiation by means of the change of temperature of an absorbing material are classified as thermal detectors. Thermal detectors respond to any wavelength radiation that is absorbed and can be made to respond over a wide range of wavelengths. One of the most common thermal detectors used in the infrared (IR) applications is the thermopile. Thermopile detectors are voltage-generating devices, which can be thought of as miniature arrays of thermocouple junctions. Dexter Research Center's unique energy absorbing material allows their thermopile detectors to have a spectral response that is essentially flat from the ultraviolet to the far infrared. The Dexter thermopile detectors are ideal for use as radiometers because of their broadband IR responsivity. In addition to the standard line, Dexter Research Center also designs custom thermopile detectors. Their 25+ years of expertise can help you achieve the best performing thermopile detectors for your applications.

Click for key to photo Drawing is a pdf file which requires Adobe Acrobat Reader - click link to download it if you don't have it.   RELATED PRODUCTS Infrared filters

Thermopile Detector Types: 1. New LOW COST Silicon Thermopiles 2. Single & Multi-channel Bismuth-Antimony thin film thermopile detectors 3. Single & Multi-channel Silicon-based thermopile detectors 4. New Silicon Linear arrays

Features:

• Flat spectral response from the ultraviolet to the far infrared
• No 1/f or microphonic noise
• Hermetically sealed

Options:

• Thermal Compensation
• Inert Gas Backfill (Ne, N2, Ar, or Xe) to customize performance
• Over 120 different Optical filters and windows in stock
• Internal apertures
• Choice of package aperture sizes
• Internal and external amplifiers
• Internal heatsinks
• Calibration services

Applications include:

• Non-contact temperature measurement
• Spectrometers
• Tympanic thermometers
• Gas analysis
• Process temperature monitoring
• Fire & flame Detection
• Household appliances
• Explosion detection
• Radiometers
• Presence monitor

Dexter Research Thermopile Detector / Sensor Selector

Click on the part numbers below to view datasheets.
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Technical Notes:

Introduction to Thermopile Detectors

Thin Film versus Silicon Based Thermopile Detectors
Comparison of thin film and silicon based thermopile detectors

A simple DC Radiometer
Basic theory for DC Radiometry and an example of a simple temperature sensor using the thermopile

Temperature Compensation of a DC Radiometer
Since a thermopile is an array of thermocouples, the temperature of the cold junction of the thermocouple must be known to provide an accurate temperature measurement. This brief describes a method for dealing with a variation in the cold junction temperature.

Accurate Temperature Measurements using Non-Contact Temperature Sensors
Digitally based non-contact temperature sensors open up the possibility of applying more accurate corrections for target/environment conditions by using the computational power of the controlling PC or micro-controller.

Amplifier Circuits
Typical amplifier circuits for use with thermopile detectors as well as the equivalent circuit of a thermopile detector. Also see the Miniature Amplifier PCB and the 1010 Amplifier.

Emissivity Correction for a Radiometer
The optical power emitted by a target will depend on its emissivity and temperature. A simple technique to take into account the change in emissivity is described.

Variations in Calibration of Radiometers using Cut-on Optical Filters
The amount of optical energy falling on the thermopile  depends on the transmission characteristic of the filters used as the window in the detector. The effect of the variation in bandwidth of the filter on the calibration of a radiometer is discussed.

Thermopile Time Constant Determination
Methods for measuring the time constant of a thermopile

Detector Normalized Angular Response
The normalized angular response for a standard thermopile package

Detector Normalized Response as a Function of Frequency
The frequency response of thin film and Silicon based thermopiles for sinusoidally modulated radiation

Blackbody Spectral Radiance
Calculation of the blackbody radiance for three spectral regions of commonly used filters

Detector Signal Calculation
The calculation of detector signal in a reflective optical system

Detector Options

All links are to pdf files and require Adobe Acrobat Reader - click link to download it if necessary

• Windows and filters in stock from wide band pass to selective narrow band pass applications. 

• Back-fill Gas has specific thermal conductivity and affects the sensitivity and time constant of the detector.

• Diffractive Lens specifically designed for Long Wave Infrared (LWIR) applications.

• Thermistors are available for installation in the package for applications that require temperature monitoring of the detector.

• Amplifiers - See the Miniature Amplifier PCB and the 1010 Amplifier.

• Apertures - Field of view can be modified using apertures in the covers or inside the package.  Apertures are also useful in eliminating cross talk in multi-channel detectors.

• Internal Heat Sinks - Decrease the thermal resistance between the detector substrate and cold junctions to the detector header and packaging. An integral heat sink thermally connects the detector cold junctions to the package allowing the detector package to be externally heat sinked for ambient temperature stability.  Internal heat sinks are available on most models except the models 6M, ST, and array detectors.

• Calibration services - Detectors can be calibrated to a standard black body source traceable to NIST for reference.