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Instrumentation and Controls > Temperature Measurement > Flashcards

Temperature Measurement Flashcards

1
Q

Few degrees of variation from the
the optimum temperature often results in very little production of the desired product—instead, the waste product is created.

A

PRODUCT QUALITY AND YIELD

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2
Q

Accurate temperature measurements increase process efficiency.

A

EFFICIENCY

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3
Q

Temperatures can increase rapidly in exothermic (giving off heat) chemical
reactions—if the temperatures are not closely watched and controlled, explosions could result.

A

SAFETY

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4
Q

Inaccurate temperature measurements during custody transfer applications result in over- or undercharging of customers.

A

CUSTODY TRANSFER

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5
Q

Temperature is a measurement of?

A

Intensity of heat

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6
Q

It is a form of energy caused by the activity of a substance’s molecules.

A

Heat

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7
Q

It is thought of as the degree of hotness or coldness of a liquid, solid or gas

A

Temperature

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8
Q

The three temperature measurement scales in use today are?

A

Fahrenheit
Celsius (also called Centigrade)
Absolute (Kelvin and Rankine)

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9
Q

They use thermal expansion of a fill fluid to provide temperature sensing and measurement.

A

Filled systems

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10
Q

Three categories of filled system

A

Glass stem thermometers
Filled thermal systems
Temperature switches

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11
Q

They have a liquid-filled fluid in a bulb or reservoir, a hollow glass tube for the fluid to expand in, and a temperature scale etched along the hollow tube.

A

Glass stem thermometers

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12
Q

The fill fluid used by Glass stem thermometers.

A

Mercury or dyed alcohol

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13
Q

Parts of the Glass stem thermometers

A

Bulb - Contains the thermometric liquid
Stem - Glass tube with a capillary bore where the liquid moves with a change in temperature
Scale - Narrow-temperature-range scale for reading a reference temperature.

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14
Q

It is similar to a pressure gauge. Instead of sensing pressure, it responds to temperature change.

A

Filled thermal system

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15
Q

The Scientific Apparatus Makers Association (SAMA) assigned filled thermal systems to four classes, what are these?

A

Class 1 - liquid fill
Class 2 - liquid/vapor fill
Class 3 - gas fill
Class 5 - mercury fill

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16
Q

These are essentially liquid-filled thermometers

A

Class 1 Liquid Filled Systems

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17
Q

These systems have a fill fluid medium that consists of a volatile liquid at equilibrium with its vapor. These are essentially vapor-pressure thermometers

A

Class 2 Systems

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18
Q

These systems use inert gas and are confined in almost constant volume

A

Class 3 Systems

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19
Q

These systems use mercury as the fill fluid. The mercury fill fluid provides a linear and faster response to temperature changes than Class 1 systems

A

Class 5 Mercury Filled Systems

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20
Q

It provides high or low-temperature detection. It may consist of a bulb, capillary tubing, and electrical switch element.

A

Temperature Switch

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21
Q

These are non-contacting temperature measurement technology that measures the amount of radiant energy a heated object emits

A

Pyrometric Devices

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22
Q

This device measures the temperature of materials that emit energy in the visible spectrum

A

Optical Pyrometers

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23
Q

This device measures temperature using an electrical radiation detector that can detect from infrared to ultraviolet wavelengths.

A

Radiation Pyrometers

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24
Q

These are devices that are made of metal oxide which either increases in resistance with an increase in temperature or decreases in resistance with an increase in temperature.

A

Thermistors

25
Q

RTds and T/Cs have several construction characteristics in common, these are?

A

Sensing element
Sensor sheath
Lead wires
Threaded adaptor (optional)

26
Q

It is located at the tip of the temperature sensor on the end that is exposed to the process temperature.

A

Sensing element

27
Q

Also called cable housing. Constructed of metal and holds most of the parts of the temperature sensor.

A

Sensor Sheath

28
Q

These are attached to the sensing element and then passed through the sensor sheath. It connects the sensing element to either the Distributed Control System or to a temperature transmitter,

A

Lead Wires

29
Q

It is welded over the rear housing of the sensor sheath. It is threaded into a thermowell or directly into the process piping.

A

Threaded adaptor

30
Q

It operates on the principle that the electrical resistance of a metal increases as temperature increases, a phenomenon known as thermosensitivity.

A

Resistance Temperature Detectors

31
Q

The three types of resistance metals most commonly used to construct RTDs are?

A

platinum, copper, and nickel.

32
Q

These are the most common types of RTD elements used in process industries. These have high accuracy, high repeatability, and a high resistance change per degree of temperature change.

A

Platinum

33
Q

These RTD element materials are highly linear throughout their temperature range but have limited accuracy and a narrower temperature range than platinum elements. Copper elements are most often used for measuring temperature in bearings and motor windings—applications in which accuracy is not critical.

A

Copper

34
Q

These RTD elements have a high resistance change per degree of temperature change
but have poor linearity, limited accuracy, and a relatively narrow temperature range. Nickel elements are most commonly used in applications in which accuracy is not critical.

A

Nickel

35
Q

Two of the most common designs of RTD sensing element

A

Wire wound
Thin film

36
Q

These RTD elements are very sturdy and reliable. Compared to thin-film RTD
elements, their accuracy tends to be higher, but their time response tends to be slightly slower.

A

Wire wound

37
Q

These RTD sensing elements are constructed by depositing a thin film of
resistance metal onto a ceramic substrate (base piece) and trimming the metal to
specifications. This RTD sensing element is faster but accuracy is lower

A

Thin film

38
Q

This RTD design is commonly used in industrial applications.

A

Three-wire RTD

39
Q

This RTD design is used primarily in the Fourlaboratory where close accuracy is required.

A

Four-wire RTD

40
Q

This determines temperature by measuring voltage.

A

Thermocouple

41
Q

Several types of T/Cs are available, each differing by the metals used to construct the element. The T/C categories are?

A

*Type E—Chromel and constantan
*Type J—Iron and constantan
*Type K—Chromel and alumel
*Types R and S—Platinum (Pt) and rhodium (Rh) (differing in the % of platinum)
*Type T—Copper and constantan

42
Q

This type of T/Cs have the highest
output (most sensitive) and can be used over a wide range of temperatures.

A

Type E

43
Q

This type of T/Cs are among the first thermocouples to be widely used. The
materials are rugged, but iron wire is susceptible to oxidation, especially at high
temperatures.

A

Type J

44
Q

This type of T/Cs are the most popular T/C type in industrial environments. They are commonly used for high-temperature applications. Because they are relatively inexpensive and offer a wide measurement range.

A

Type K

45
Q

This type of T/Cs are useful for extremely high-temperature measurements. Because they are constructed from a platinum alloy, they are expensive and are used only when the process temperatures are too high
for other T/Cs to function properly.

A

Type R and S

46
Q

This type of T/Cs are generally used in very low-temperature (cryogenic) applications. These elements are robust in high-humidity environments.

A

Type T

47
Q

For good performance, the hot junction must be constructed to be?

A

mechanically sound, electrically continuous, and not poisoned by the chemical ingredients of welding or brazing
materials

48
Q

This hot junction configuration creates improved thermal conductivity, which in turn gives the quickest response time but is susceptible to noise.

A

Grounded

49
Q

This hot junction configuration has a slightly slower response time than grounded junctions, but are not susceptible to electrical noise.

A

Ungrounded

50
Q

These hot junction configurations are at the same temperature, but both junctions
will typically fail at the same time

A

Unisolated

51
Q

These hot junction configurations may or may not be at the same temperature. Reliability of each junction is increased, however, because a failure of one junction does not cause a failure in the second junction

A

Isolated

52
Q

This material is a closed-end, metal tube that encapsulates and protects a sensor from process flow, pressure, vibration, and corrosion.

A

Thermowell

53
Q

Thermowells are constructed of one of several materials, some of which are?

A

316 and 304 stainless steel
Carbon steel
Monel®
Inconel 600
Hastelloy®

54
Q

Three factors affect the choice of material in a thermowell

A

*Type of corrosive environment to which the thermowell will be exposed
*Temperature and pressure limits of the material
*Compatibility with the process piping material to ensure solid, noncorroding welds and junctions

55
Q

Thermowells can be mounted in one of three methods, these are?

A

Threaded
Welded
Flanged (Bolted)

56
Q

This mounting method enables
them to be easily installed and removed. These are the weakest type of thermowell and may leak.

A

Threaded

57
Q

This mounting methods are permanently welded onto the process pipe or tank. These are the strongest type of thermowell and are used with fluids of high velocity, high temperature, or high pressures

A

Welded

58
Q

This mounting methods are bolted onto a pipe or tank and can be easily removed or installed. These are used in corrosive environments as well as in high-velocity, high-temperature, or high-pressure applications.

A

Bolted (Flanged)

59
Q
A

Instrumentation and Controls (1 decks)

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