Pneumatic infrared detector

Golay, M. J. E. (1947). A pneumatic infrared detector. Review of Scientific Instruments, 18,357-62. 

Some proportional detectors are combined in the same instrument with a suitable transducer which can perform some of the functions of a controller. For example, for pneumatic systems the primary sensing element actuates a variable air jet, thus modulating an air pressure which is transmitted to a further controller or direct to the controlled device. Electric and electronic detectors such as the infrared detector include the sensing and amplifying circuits of the instrument. 

Kenny et al. (1991) Novel infrared detector based on a tunneling displacement transducer by T. W. Kenny, W. J. Kaiser, S. B. Waltman, and J. K. Reynolds. Appl. Phys Lett. 59,1820-1822. Describes micromachined silicon pneumatic cell with an electronic displacement transducer. Performance of prototypes is competitive with the best mcooled infrared detectors. 

Fire detectors—dry-pilot head and pneumatic rate-of-rise heat detectors are the most frequent devices used. A dry pilot head detection systems uses 165°F (74°C) V2-in sprinkler head with air pressure maintained in the piping. When the sprinkler opens the air is released resulting in the sprinkler valve opening. Other types of detectors include ultraviolet, infrared flame detectors, or thermostatic cable heat detection. 

A pneumatic detector consists of a small cylindrical chamber that is filled with xenon and contains a blackened membrane to absorb infrared radiation and heat the gas. One end of the cylinder is sealed with a window that is transparent to infrared radiation the other end is sealed with a flexible diaphragm that moves in and out as the gas pressure changes with cooling or heating. The temperature is determined from the position of the diaphragm. 

The polarization measurements in the mid-infrared (IR) and near-infrared (NIR) were performed on a Bruker IFS 88 FTIR/FTNIR spectrometer utilizing a wire-grid polarizer on KRS5-substrate which could be rotated pneumatically parallel or perpendicular to the selected reference direction. For the experiments in the step-scan mode a mercury-cadmium-telluride (MCT) detector with a DC-coupled preamplifier was used. This allowed an absolute intensity at each mirror position to be recorded and the use of phase-modulation-demodulation techniques, which are often applied for the step-scan mode [28-30] to be avoided. Further specific instrumental details of the individual applications are given in the corresponding sections. 

The requirement for use of IS devices does not restrict a designer. Rather it directs them to certain choices of equipment which have been designed for and are certified by lEC as available for use in hazardous areas with intrinsically safe barriers including 4—20 milliamp (mA) DC two-wire transmitters, thermocouples, resistance temperature detectors (RTDs), strain gages, pressure, flow, level switches, current/ pneumatic (l/P) converters, solenoid valves, proximity switches, infrared temperature sensors, potentiometers, EED indicating lights, and flowmeters with magnetic pickups. 

Chevrier J-B, Baert K, Slater T, Verbist A (1995) Micromachined infrared pneumatic detector for gas sensor. Microsyst Technol 1 71-74... 

Pneumatic Detectors. The third type of detector which has been used in infrared spectrophotometers is the pneumatic detector, which is an extremely sensitive gas thermometer. The radiation which reaches the sensitive element or receiver heats the enclosed gas. The resulting small rise in pressure is converted to an electrical signal by one of several possible methods. The most commonly applied version of a pneumatic detector is the Golay cell, whose receiver is an aluminum-coated plastic. In this case the receiver does not necessarily depend on a black coating... 

Another temperature to voltage conversion mechanism, used in pneumatic detectors, is based on the gas thermometer. The best known representative of this type of detector is the Golay cell. The infrared absorber is imbedded in a small volume of gas contained in a sealed cell. Radiation heats the absorber and the surrounding gas. The associated increase in pressure causes a small displacement of a thin membrane. In the Golay cell this displacement is sensed by the deflection of an external light beam and registered by an appropriate detector (Golay 1947 ... 

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