Optical pyrometer, operation

Look up and then describe the physical principles on which the operation of the following thermometers is based (a) semiconductors, (b) paramagnetic salts, (c) optical pyrometers, (d) thermocouples. 

In this section, the design and operation of familiar liquid thermometers, thermocouples, platinum resistance thermometers, thermistors, and optical pyrometers are discussed in detail. Briefer descriptions are also given of a variety of special thermometric devices such as quartz thermometers, germanium resistance thermometers, and sihcon-diode thermometers. 

The Shore pyroscope. Fig. 17, operates upon a principle very similar to that of the Fery optical pyrometer. The instrument has a scale graduated to read temperatures directly, which is a material advantage. The design of optical parts is rather un-... 

Temperatures are measured with a Pyro optical pyrometer, or, for temperatures below 750°C, a calibrated thermocouple. The entire cell assembly may be moved freely in the x, y, and z directions during operations, for exact alignment. 

Pyrometer pl- ra-mo-tor n [ISV] (1796) (1) Instrument for measuring temperatures beyond the upper limit of the usual liquid thermometer. They may operate on the differential expansion of two metallic strips joined together, the measurement of changes of resistance, and the measurement of current flowing through two joined pieces of metal. In addition, radiation pyrometers are based on the measurement of heat radiated from a hot body, and optical pyrometers on the measurement of the intensity of light emitted from a hot body. (2) An Infrared Pyrometer. 

Localized overheating of a tube causes localized high-temperature creep. This leads to the plastic deformation of a tube and hence thin tube walls. Such hot spots are indicated by the color of the tube, as shown in Table 30.1. This chart is not a function of the material of the tube. Carbon steel tubes, as well as tubes of all alloys, glow with a color that corresponds only to the localized tube temperature. This is the principle of operation of the optical pyrometer, a device that is widely used in the process industry to remotely measure tube skin temperatures. 

There are two distinct pyrometric instruments, the radiation thermometer and the optical pyrometer, which are described in greater detail in the following subsections. Both pyrometers utilize radiation energy in their operation. Some of the basic laws of radiation transfer of energy will be described briefly. 

Figure 8.10 Schematic of Ardocol two color pyrometer. The optical aiming system allows an operator to site the device so that only the target is in view [15).

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