Temperature measurement instrument

As normally used in the process industries, the sensitivity and percentage of span accuracy of these thermometers are generally the equal of those of other temperature-measuring instruments. Sensitivity and absolute accuracy are not the equal of those of short-span electrical instruments used in connection with resistance-thermometer bulbs. Also, the maximum temperature is somewhat limited. 

If an instrument or instrument system malfunctions, the operator tries to correct the problem. If an alarm, flow or temperature measuring instrument or shut down system malfunctions, the operators first response should be an attempt to restore it to service. It may be a... 

If an instrument or instrument system malfunctions, the operator tries to correct the problem. If an alarm, flow- or temperature-measuring instrument or shutdown system malfunctions, the operator s first response should be an attempt to restore it to service. It may be a plugged impulse line, inadvertent flow shut off to an analyzer, etc. If the Instrument System is a Class 1 or 2, immediately go to Step 2. If the alarm is a Class J. the Lead Operator (or Shift Foreman) should be consulted and follow established procedures and his knowledge of the unit and the specifics of the situation to determine the temporary steps required. At the minimum, a note in the maintenance logbook must be made to initiate repairs. Stop Here for Class 3 Alarms. 

Dry-bulb temperature, T—the abscissa of the chart. This is the air temperature as measured by a thermometer, thermocouple, or other conventional temperature-measuring instrument. 

The psychrometric chart (oT humidity chart) conlam values of a number of process variables for air-water vapor systems at 1 atm. The values listed on the chart include dry-bulb temperature (the temperature measured by common temperature-measurement instruments), moisture content or absolute humidity (mass ratio of water vapor to dry air), relative humidity, humid volume (volume per mass of dry air), wet-bulb temperature (the temperature reading on a thermometer with a water-saturated wick around the bulb immersed in a flowing stream of humid air), and enthalpy per mass of dry air. If you know the values of any two of these variables for humid air at or near 1 atm, you can use the chart to determine the values of the other four, which can greatly simplify material and energy balance calculations. 

The expansion on heating is most marked in the case of gases, and was noticed first in them as early as 100 b.c., we find this property of gases made use of by Hero of Alexandria in some ingenious experiments. In the case of liquids and solids the expansion is much less noticeable in the latter case it is even somewhat difficult to determine. Gases and liquids are most suitable for the measurement of temperature, and for the construction of temperature measuring instruments, or thermometers, as they are called. 

Figure 1.3 Temperature measuring instruments span the range from near absolute zero to beyond 3000 K. The chart indicates the preferred methods of thermal instrumentation for various temperature regions.

Later developments in temperature measurement employed knowledge about the relationship between temperature and radiation emission, measurable on a spectrometer. Probably first used by H. Le Chatelier in 1892, such a device was termed an optical pyrometer. Another temperature-measuring instrument based on radiation from a hot surface was the total radiation pyrometer. This device was proposed by C. Fery in 1902 and modified by others (Fery, 1902). 

The former case is realized in nature in the expansion of ideal gases and the mixture of dilute solutions the most important temperature measuring instrument, the air thermometer, depends upon this fact. 

Temperature Measurement Instruments and Apparatus, ASME-PTC 19.3-1974, supplement to ASME performance test codes, 1974. 

N. E. Hager, Jr., Thin Foil Heat Meter, Rev. Sci. Instrum., 36, pp. 1564-1570 and 1965.62. Temperature Measurement Instruments and Apparatus, ASME-PTC 19.3-1974, supplement to ASME performance test codes, 1974. 

These can be used over a very wide range. Their principle of operation is based on the large temperature coefficient of electrical resistance of Pt and Ni (for example, the resistance of Pt changes by 0.4% per degree). These thermometers are among the most accurate temperature measuring instruments. It is not difficult to make a resistance thermometer in the laboratory, but the commercial instruments are preferable. The high-temperature type consists of a mica cross inserted in a thin-wall quartz tube. A fine double Pt filament is wound around the mica cross. 

RECORDING THERMOMETER - Temperature measuring instrument which has a pen marking a moving chart. 

There are many types of temperature-measuring instruments available, and. while the electronic versions are very widely used, the ordinary mercury-in-glass or alcohol-in-glass thermometers are still prevalent. There is more that can go wrong with a mercury-in-glass thermometer than is often appreciated, so there is a need to have them calibrated frequently, and the mercury thread should be examined for continuity before u.se. For... 

ISO 653. Temperature measuring instruments—Long solid-stem thermometers for precision use, 1980. 

A pyrometer is a non-contacting temperature measurement instrument that is usually used for temperatures above 500 °C, although with some modifications it can measure temperatures below room temperature. The word pyrometry comes from the Greek words pyro (Are) and meter (measure). The basic principle relies on the notion that all bodies emit thermal radiation proportional to their temperature. Pyrometers detect this thermal radiation and through Planck s law the temperature can be determined. 

Dial thermometers, standardised temperature measuring instruments... 

Thermocouples are the most common temperature measurement devices. A detailed description of thermocouples and other temperature measuring instruments and sensors can be found in Holman (1994) or Stephenson et al. (1999). Maximum temperature limit, up to which a thermocouple can be used without damage, depends strongly on its diameter and the surrounding environment. The thicker the thermocouple, the higher the temperature application limit, but on the other hand the longer the response time. 

Now that digital temperature measuring instruments are available it is possible to get accurate readings of the temperature of the thermocouple probe. However, the temperature of the probe is not necessarily the temperature of the rubber. 

Measurement of temperature is generally considered to be one of the simplest and most accurate measurements performed in engineering. The desired accuracy in the measurement can be obtained, however, only by observing suitable precautions in the selection, installation, and use of temperature-measuring instruments and in the proper interpretation of the results obtained with them. 

A thermocouple thermometer is a temperature-measuring instrument in which the electromotive force developed in a circuit composed of two dissimileu metals is used as a means of temperature measvu ement. It consists of a device for measuring electromotive force, a sensing element (thermocouple), and electrical conductors operatively connecting the two. 

Hybrid inventory measurement system. The hybrid inventory measurement system (HIMS) combines the most modern level gauging techniques with hydrostatic tank gauging (Figs. T-13 and T-14). It utilizes an advanced radar or servo level gauge for accurate level measurement, with a smart pressure transmitter (PI) and a temperature measurement instrument. On nonatmospheric tanks a second transmitter for the vapor pressure compensation is required. 

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