Thermopile detectors

The beam was then made divergent with a lens. The wafer holder was positioned to ensure a uniform exposure of the resist. In line with the wafer holder was a Scientech 365 Power and Energy Meter equipped with a 2.5 cm diameter thermopile detector. Power/ pulse/cm was obtained while the laser was in a free running mode. The number of pulses needed for a particular dose was calculated. The laser was then triggered and controlled with a Hewlett Packard Model 3314A Pulse Generator. 

A particular kind of quantum detector (or photodetector) used in laboratories and industry is known as the thermopile detector. In an experiment, it is desired to measure the radiation from a black flat plate extending to infinity, A detector has been placed parallel to the plate. The catalog of the detector indicates that the maximum allowable incident radiation is 200 mW/oii5. Determine the highest tolerable plate temperature which will not damage the thermopile detector. Neglect the radiation emitted by the detector itself. 

Fig. 6.3 Open-circuit potential (OCP) of three p-GaAsPN compositions [5, 6] ( g 1.8 eV) plotted versus illumination intensity [7]. The light source used for these measurements was a fiber optic illuminator equipped with a 150-Watt tungsten bulb, and the intensity was measured using an optical power meter with a thermopile detector. At 0.6 W/cm (piDximating six Suns of intensity), OCP is nearing saturation for this material/lamp combination...

The intensity of the monochromatic light (Emono) is recorded with a power meter equipped with a thermopile detector, calibrated silicon photodiode, or calibrated spectrophotometer (see section Limitations of the Technique) the photo-current 7ph is obtained from the chronoramperometry experiment and usually represents an average steady-state value over a set period of time (at least several seconds). The number of photogenerated electrons can be calculated from the photocurrent using the following. 

K by radiation to space. With thermostatic control the thermopile detector and all optical elements are accurately held at the same temperature. 

Kanno et al. (1994) Uncooled infrared focal plane array having 128 x 128 thermopile detector elements by T. Kanno et al. (14 authors listed). Proc. SPIE 2269,450. This paper describes an array with 0.5 °C NETD w/f/I lens. Cited by Foote et al. (1997). 

During the Vietnam War, infrared detection systems were used to remotely count troop movements. Thermopile-based systems were hidden near roads, and counts were radioed to safe locations. Later, this technology was commercialized for consumer and industrial security applications. These applications rely on relatively low-cost pyroelectric and thermopile detectors. Tutorials and overviews may be found on the vendor websites - see Section 6.8. 

Dexter Research Accessed 8 May 2013 at http //www.dexterresearch.com/7module =Home. Dexter produces IR thermopile detectors their web site provides information covering a wide variety of useful subjects. 

Electro Optical Components Inc Web Site (2014) by Electro Optical Components, Inc., Santa Rosa, CA. Accessed April 2014 at http //www.eoc-inc.com/infrared source.htm. Sources and Pyroelectric Detectors, Thermopile Detectors, Infrared Filters. 

Total Radiation Pyrometers In total radiation pyrometers, the thermal radiation is detec ted over a large range of wavelengths from the objec t at high temperature. The detector is normally a thermopile, which is built by connec ting several thermocouples in series to increase the temperature measurement range. The pyrometer is calibrated for black bodies, so the indicated temperature Tp should be converted for non-black body temperature. 

Another application of the Seebeck effect is to be found ill detectors of small quantities of heat radiation. These sensitive detectors comprise a thermopile, a pile of thermocoup)les (small pieces of two different metals connected in V form and put into series). Half of the junctions of the thermopile are shielded within the detector, whereas the other half are exposed to... 

Early bolometers used, as thermometers, thermopiles, based on the thermoelectric effect (see Section 9.4) or Golay cells in which the heat absorbed in a thin metal film is transferred to a small volume of gas the resulting pressure increase moves a mirror in an optical amplifier. A historical review of the development of radiation detectors until 1994 can be found in ref. [59,60], The modern history of infrared bolometers starts with the introduction of the carbon resistor, as both bolometer sensor and absorber, by Boyle and Rogers [12], The device had a number of advantages over the Golay cell such as low cost, simplicity and relatively low heat capacity at low temperatures. 

E. H. Putley, The Pyroelectric Detector Norman B. Stevens, Radiation Thermopiles... 

We expect these micromachined sensors to become more and more important in the household industry, in many domestic applications of silicon pressure sensors, acceleration sensors, tilt sensors, infrared detectors and thermopiles, flow meters, as well as gas sensors and liquid constituent sensors. 

C02-IR detection systems for example contain a light source emitting infrared light ideally at wavelengths around 4.2 pm (often a simple light bulb), an absorption path (the so called cuvette), a spectral filter and a detector (thermopile). The filter is normally integrated into the detector housing. 

A liquid flow microcalorimeter, the thermal activity monitor (TAM), is commercially available from ThermoMetric (formerly LKB/Bofors). This instrument consists of two glass or steel ampules with a volume of 3 to 4 cm3 (25 cm3 ampule available with a single detector), placed in a heat sink block. Recently, an injection-titration sample vessel was developed which acts as a microreactor. This vessel is provided with flow-in, flow-out, and titration lines, with a stirring device. The isothermal temperature around the heat sink is maintained by a controlled water bath. Each vessel holder, containing an ampoule, is in direct contact with a thermopile array, and the two arrays are joined in series so that their output voltages subtract. The two pairs of thermopile arrays are oppositely connected to obtain a differential output,... 

Figure 3.13 The spectral dependence of the specific detectivity for several photoconduction detectors. The values corresponding to a typical thermopile and to a typical piroelectric detector are also shown.

The temperature of the block, which works as a heat sink, is controlled very precisely. The heat generated in the system flows to the heat sink and is accurately measured by means of a detector. This is made up of a large number of identical conductive thermocouples (a thermopile) that surround the vessel and connect it to the block in such a way that the vessel and the block temperatures are always close to each other. 

FIGURE 3.17 Typical device (Eppley Laboratories Model 8-48) used to measure solar irradiance. The detector consists of a differential thermopile with the hot junction receivers blackened with flat black coating and the cold junction receivers whitened with BaS04 (photo supplied courtesy of G. L. Kirk, Eppley Laboratories). 

The most recent generation of NDIR analyzers have evolved to satisfy the frequently harsh industrial environments encountered. These analyzers utilize solid-state sensors for the detection of infrared radialion. Most frequently used sensors are lead selenide (PhSc). thermopiles, or pyroelectric detectors. The gas analyzers generally are configured as single-path instruments, dual-beam with a reference palh. or dual-channel with a reference filter. 

Several thermocouples may be connected in series in order to increase the sensitivity of the instrument. This arrangement is called a thermopile and, for n identical thermocouples, gives an output which is n times greater than that from a single thermocouple. Thermopiles are frequently used to detect and measure heat radiation (Section 6.4.2). In this case the surface of the detector is blackened to maximise the absorption of the incoming radiation. 

These instruments employ a blackened thermopile as a detector and focus the radiation using lenses or mirrors. For a given source temperature T, the incoming radiation heats the measuring junction until losses due to conduction, convection and radiation just balance the heat input, i.e. 

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