《纺织复合材料》课程参考文献（Composite Materials Handbook，Volume 1）CHAPTER 6 LAMINA, LAMINATE, AND SPECIAL FORM CHARACTERIZATION

MIL-HDBK-17-1F Volume 1,Chapter 6 Lamina,Laminate,and Special Form Characterization changes in the wiring between the input and output ends do not affect the output voltage,provided that the wiring is of thermocouple alloy or a thermoelectric equivalent.For example,if a thermocouple is measuring temperature in a furnace and the instrument that shows the reading is some distance away, the wiring between the two could pass near another furnace and not be affected by its temperature,un- less it becomes hot enough to melt the wire or permanently change its electrothermal behavior. Thermocouples have advantages over other contact sensors in that they are simple,rugged,inex- pensive,require no external power,are available in a wide variety of forms,and can be used over wide temperature ranges.Disadvantages of thermocouples are that they are nonlinear,produce very low volt- ages,and require an external temperature reference. Alloy A +O T2 Vab -O Alloy B Figure 6.4.5.2 Schematic of thermocouple junction. Thermocouples must be selected to meet the conditions of the application.Only general recommen- dations on size and type can be given.Some of the considerations involved are length of service,tem- perature,atmosphere,and desired response time.Smaller gauge sizes provide faster response at the expense of service life at the elevated temperatures.Larger gauge sizes provide longer service life at the expense of response time.As a rule,it is advisable to protect thermocouple elements with a suitable pro- tecting tube or drilled well. Thermocouples are available in different combination of metals or 'calibrations'.The four most com- mon calibrations are J,K,T,and E.Each calibration has a different temperature range and environment, although the maximum temperature varies with the diameter of the wire used in the thermocouple. Type J:[lron(+)Constantan(-)] Maximum recommended operating temperature is 1400F(760C). Type K:[CHROMEL (+ALUMEL(-)] Maximum recommended operating temperature is 2300F(1260C). Type T:[Copper(+)Constantan(-)] Recommended operating temperature range is-328 to 662F(-200 to 350C). Type E:[CHROMEL (+)Constantan(-)] Maximum recommended operating temperature is 1652F(900C). 6.4.5.3 Metallic resistive temperature devices Resistance temperature devices(RTDs)rely on the temperature dependence of a material's electrical resistance.They are usually made of a pure metal having a small but accurate positive temperature coef- ficient.A typical metallic RTD consists of a fine platinum wire wrapped around a mandrel and encased in a protective coating.Usually,the mandrel and coating are glass or ceramic.The resistance of the plati- num wire rises more or less linearly with temperature.By measuring the resistance of the wire,its tem- perature can be determined.RTDs made of platinum wire are well characterized and linear from-434 to 1112F(-259to600C). Although the response of an RTD is more stable and linear than that of a thermocouple,RTDs cannot be used over as broad a temperature range as thermocouples.The large thermal mass and poorer ther- 6-21

MIL-HDBK-17-1F Volume 1, Chapter 6 Lamina, Laminate, and Special Form Characterization 6-21 changes in the wiring between the input and output ends do not affect the output voltage, provided that the wiring is of thermocouple alloy or a thermoelectric equivalent. For example, if a thermocouple is measuring temperature in a furnace and the instrument that shows the reading is some distance away, the wiring between the two could pass near another furnace and not be affected by its temperature, un￾less it becomes hot enough to melt the wire or permanently change its electrothermal behavior. Thermocouples have advantages over other contact sensors in that they are simple, rugged, inex￾pensive, require no external power, are available in a wide variety of forms, and can be used over wide temperature ranges. Disadvantages of thermocouples are that they are nonlinear, produce very low volt￾ages, and require an external temperature reference. Alloy A Alloy B T2 T1 Vab + - Figure 6.4.5.2 Schematic of thermocouple junction. Thermocouples must be selected to meet the conditions of the application. Only general recommen￾dations on size and type can be given. Some of the considerations involved are length of service, tem￾perature, atmosphere, and desired response time. Smaller gauge sizes provide faster response at the expense of service life at the elevated temperatures. Larger gauge sizes provide longer service life at the expense of response time. As a rule, it is advisable to protect thermocouple elements with a suitable pro￾tecting tube or drilled well. Thermocouples are available in different combination of metals or ‘calibrations’. The four most com￾mon calibrations are J, K, T, and E. Each calibration has a different temperature range and environment, although the maximum temperature varies with the diameter of the wire used in the thermocouple. Type J: [Iron (+) Constantan (−)] Maximum recommended operating temperature is 1400°F (760°C). Type K: [CHROMEL (+) ALUMEL (−)] Maximum recommended operating temperature is 2300°F (1260°C). Type T: [Copper (+) Constantan (−)] Recommended operating temperature range is −328 to 662°F (−200 to 350°C). Type E: [CHROMEL (+) Constantan (−)] Maximum recommended operating temperature is 1652°F (900°C). 6.4.5.3 Metallic resistive temperature devices Resistance temperature devices (RTDs) rely on the temperature dependence of a material’s electrical resistance. They are usually made of a pure metal having a small but accurate positive temperature coef￾ficient. A typical metallic RTD consists of a fine platinum wire wrapped around a mandrel and encased in a protective coating. Usually, the mandrel and coating are glass or ceramic. The resistance of the plati￾num wire rises more or less linearly with temperature. By measuring the resistance of the wire, its tem￾perature can be determined. RTDs made of platinum wire are well characterized and linear from −434 to 1112°F (−259 to 600°C). Although the response of an RTD is more stable and linear than that of a thermocouple, RTDs cannot be used over as broad a temperature range as thermocouples. The large thermal mass and poorer ther-

MIL-HDBK-17-1F Volume 1,Chapter 6 Lamina,Laminate,and Special Form Characterization mal coupling combine to produce slow response to temperature changes.The RTD responds to me- chanical,as well as thermal strains,making it sensitive to loads and vibration,in addition to temperature Unlike the thermocouple,the RTD is not self-powered.Since a current must be passed through the de- vice to provide a voltage that can be measured,the device is prone to self heating.This is particularly true if a large current is employed,a small RTD is employed,or if the RTD is not well coupled thermally. 6.4.5.4 Thermistors Thermistors are generally composed of ceramic semiconductor materials that exhibit a large change in resistance with a change in temperature.There are both positive temperature coefficient(PTC)and negative temperature coefficient(NTC)devices on the market.A PTC thermistor is defined by an in- crease in resistance with an increase in temperature.A NTC thermistor is defined by a decrease in resis- tance with an increase in temperature.The majority of thermistors,however,are of type NTC. Thermistors can generally be classified into two major groups depending upon the method by which electrodes are attached to the ceramic body.The first group consists of bead type thermistors and the second group consists of metallized surface contact thermistors.All of the bead type thermistors have platinum alloy leadwires which are sintered into the ceramic body.As a group,the sealed bead type ther- mistors are more stable than the metallized surface contact type.The bead types are generally smaller in size and have faster thermal time constant values.That is an advantage in many temperature measure- ment applications.However,the bead types have lower dissipation values that result in greater self- heating effects in most applications.The metallized surface contact type thermistors are easier to manu- facture and,therefore,less expensive than the bead type thermistors.However,the metallized surface contact type thermistors are generally rated at 300F(150C)with the best continuous operating tempera- ture stability at 221F(105C)or less. Thermistors are extremely sensitive to temperature changes and can detect temperature changes that could not be observed using other devices.Although thermistors can be very accurate,their meas- urement range is small in comparison to thermocouples and RTDs.Since a current must be passed through the device to provide a voltage that can be measured,the device is prone to self heating.Ther- mistors are also somewhat more fragile than other temperature measurement devices. 6.4.5.5 Bimetallic devices Bimetallic temperature indicators take advantage of the difference in the rate of thermal expansion of different metals.Strips of two dissimilar metals are bonded together.When heated,one side of the com- posite will expand relative to the other.The resulting bending is translated to a temperature reading via mechanical linkages.These devices are portable,and require no power.However,they are not as accu- rate as other temperature measurement devices,cannot be used to make point measurements,and do not generate data in a form that can be readily recorded.They can be used to acquire a qualitative re- cord of the ambient temperature if a pen is attached to the indicating pointer,and traces a line on a mov- ing chart. 6.4.5.6 Liquid expansion devices Liquid expansion devices,typified by the liquid-column bulb thermometer,require no power,and are stable even after repeated thermal cycling.On the other hand,they do not generate data that can be easily recorded and they do not respond well to transient temperature changes.Since they must be im- mersed in the medium whose temperature is being measured,they cannot be used to make point meas- urements.Their primary use is measuring the temperature of the test environment. 6.4.5.7 Change-of-state devices Change-of-state temperature sensors consist of various labels,pellets,crayons,lacquers,or liquid crystals whose appearance changes once a certain temperature is reached.The typical response time is measured in minutes,so they do not respond well to transient temperature changes.The accuracy is 6-22

MIL-HDBK-17-1F Volume 1, Chapter 6 Lamina, Laminate, and Special Form Characterization 6-22 mal coupling combine to produce slow response to temperature changes. The RTD responds to me￾chanical, as well as thermal strains, making it sensitive to loads and vibration, in addition to temperature. Unlike the thermocouple, the RTD is not self-powered. Since a current must be passed through the de￾vice to provide a voltage that can be measured, the device is prone to self heating. This is particularly true if a large current is employed, a small RTD is employed, or if the RTD is not well coupled thermally. 6.4.5.4 Thermistors Thermistors are generally composed of ceramic semiconductor materials that exhibit a large change in resistance with a change in temperature. There are both positive temperature coefficient (PTC) and negative temperature coefficient (NTC) devices on the market. A PTC thermistor is defined by an in￾crease in resistance with an increase in temperature. A NTC thermistor is defined by a decrease in resis￾tance with an increase in temperature. The majority of thermistors, however, are of type NTC. Thermistors can generally be classified into two major groups depending upon the method by which electrodes are attached to the ceramic body. The first group consists of bead type thermistors and the second group consists of metallized surface contact thermistors. All of the bead type thermistors have platinum alloy leadwires which are sintered into the ceramic body. As a group, the sealed bead type ther￾mistors are more stable than the metallized surface contact type. The bead types are generally smaller in size and have faster thermal time constant values. That is an advantage in many temperature measure￾ment applications. However, the bead types have lower dissipation values that result in greater self￾heating effects in most applications. The metallized surface contact type thermistors are easier to manu￾facture and, therefore, less expensive than the bead type thermistors. However, the metallized surface contact type thermistors are generally rated at 300°F (150°C) with the best continuous operating tempera￾ture stability at 221°F (105°C) or less. Thermistors are extremely sensitive to temperature changes and can detect temperature changes that could not be observed using other devices. Although thermistors can be very accurate, their meas￾urement range is small in comparison to thermocouples and RTDs. Since a current must be passed through the device to provide a voltage that can be measured, the device is prone to self heating. Ther￾mistors are also somewhat more fragile than other temperature measurement devices. 6.4.5.5 Bimetallic devices Bimetallic temperature indicators take advantage of the difference in the rate of thermal expansion of different metals. Strips of two dissimilar metals are bonded together. When heated, one side of the com￾posite will expand relative to the other. The resulting bending is translated to a temperature reading via mechanical linkages. These devices are portable, and require no power. However, they are not as accu￾rate as other temperature measurement devices, cannot be used to make point measurements, and do not generate data in a form that can be readily recorded. They can be used to acquire a qualitative re￾cord of the ambient temperature if a pen is attached to the indicating pointer, and traces a line on a mov￾ing chart. 6.4.5.6 Liquid expansion devices Liquid expansion devices, typified by the liquid-column bulb thermometer, require no power, and are stable even after repeated thermal cycling. On the other hand, they do not generate data that can be easily recorded and they do not respond well to transient temperature changes. Since they must be im￾mersed in the medium whose temperature is being measured, they cannot be used to make point meas￾urements. Their primary use is measuring the temperature of the test environment. 6.4.5.7 Change-of-state devices Change-of-state temperature sensors consist of various labels, pellets, crayons, lacquers, or liquid crystals whose appearance changes once a certain temperature is reached. The typical response time is measured in minutes, so they do not respond well to transient temperature changes. The accuracy is

MIL-HDBK-17-1F Volume 1,Chapter 6 Lamina,Laminate,and Special Form Characterization lower than with other types of sensors,and the change in state is irreversible,except in the case of liquid crystal displays.Change-of-state sensors can provide a handy,qualitative confirmation that a material has,or has not,reached or exceeded some temperature. 6.4.5.8 Infrared detectors Infrared(IR)detectors are noncontacting devices that measure the amount of radiation emitted by a surface.At temperatures above absolute zero,all matter radiates electromagnetic energy.The level and frequency of the radiated energy are proportional to temperature.In many engineering situations,much of the radiation is in the infrared region.If the radiating characteristics of the surface are known,its tem- perature can be inferred from the level of the infrared energy at a specific wavelength.The simplest IR detector design consists of a lens to focus the IR energy onto a detector,that converts the energy to elec- trical signals that are displayed in units of temperature after being adjusted for ambient temperature varia- tions. IR thermometers(IRT)come in a wide variety of configurations pertaining to optics,electronics,tech- nology,size,and protective enclosures.The basic IRT design is comprised of a lens to collect the energy emitted from the target;a detector to convert the energy to an electrical signal;an emissivity adjustment to match the IRT calibration to the emissivity characteristics of the object being measured;and an ambi- ent temperature compensation circuit to ensure that the temperature variations within the IRT due to am- bient changes are not transferred to the final output. Single-wavelength thermometry design measures the total energy emitted from a surface at a pre- scribed wavelength.These devices measure and evaluate the intensity,or brightness,of the intercepted thermal radiation.Intensity,or,more generally,radiance is measured in a narrow wavelength band of the thermal spectrum.Band selection is dictated by the temperature range and the type of material to be measured.The configuration can range from handheld probes with a simple remote meter to sophisti- cated portables with simultaneous viewing of target and temperature,plus memory and/or printout capa- bilities. Dual-and multi-wavelength thermometry are used in applications where absolute accuracy is critical, and where the product is undergoing a physical or chemical change.Dual-wavelength thermometry in- volves measuring the spectral energy at two different wavelengths.The target temperature can be read directly from the instrument if the emissivity has the same value at both wavelengths.The advantage of ratio measuring is that temperature readings are greatly independent of emissivity fluctuations and/or sight path obscurations.The technique is generally used for temperatures above incandescence(1300F (700C)),but measurements down to 400F(200C)are possible. Advantages of infrared detectors are that they are non-contacting,can be used to measure very high temperatures,and can be used to measure temperatures in hostile environments,provided visual access can be obtained.One disadvantage is that the surface emissivity at the temperature of interest must be known(this information is not always known).In addition,the device will average all of the temperatures in its field of view.If a target does not completely fill the field,the temperature of its background will contribute to the reading.If the target is not a perfect emitter,it will reflect infrared energy from other sources that can be detected by the device. 6.4.5.9 Calibration of temperature measurement devices The effectiveness of any temperature measuring equipment is dependent on its accuracy and its re- peatability.As with other measuring equipment,temperature devices must be calibrated and periodically verified to maintain confidence that their indicated output is within a certain known tolerance to the true value.Calibration and verification of temperature devices is simple in concept and involves merely ex- posing the device of interest and a reference device to the same temperature.Any deviation of outputs then can be corrected,in the case of calibration,or noted as in or out of tolerance,in the case of verifica- tion.For the purposes of this document,calibration and verification will be considered together and will 6-23

MIL-HDBK-17-1F Volume 1, Chapter 6 Lamina, Laminate, and Special Form Characterization 6-23 lower than with other types of sensors, and the change in state is irreversible, except in the case of liquid crystal displays. Change-of-state sensors can provide a handy, qualitative confirmation that a material has, or has not, reached or exceeded some temperature. 6.4.5.8 Infrared detectors Infrared (IR) detectors are noncontacting devices that measure the amount of radiation emitted by a surface. At temperatures above absolute zero, all matter radiates electromagnetic energy. The level and frequency of the radiated energy are proportional to temperature. In many engineering situations, much of the radiation is in the infrared region. If the radiating characteristics of the surface are known, its tem￾perature can be inferred from the level of the infrared energy at a specific wavelength. The simplest IR detector design consists of a lens to focus the IR energy onto a detector, that converts the energy to elec￾trical signals that are displayed in units of temperature after being adjusted for ambient temperature varia￾tions. IR thermometers (IRT) come in a wide variety of configurations pertaining to optics, electronics, tech￾nology, size, and protective enclosures. The basic IRT design is comprised of a lens to collect the energy emitted from the target; a detector to convert the energy to an electrical signal; an emissivity adjustment to match the IRT calibration to the emissivity characteristics of the object being measured; and an ambi￾ent temperature compensation circuit to ensure that the temperature variations within the IRT due to am￾bient changes are not transferred to the final output. Single-wavelength thermometry design measures the total energy emitted from a surface at a pre￾scribed wavelength. These devices measure and evaluate the intensity, or brightness, of the intercepted thermal radiation. Intensity, or, more generally, radiance is measured in a narrow wavelength band of the thermal spectrum. Band selection is dictated by the temperature range and the type of material to be measured. The configuration can range from handheld probes with a simple remote meter to sophisti￾cated portables with simultaneous viewing of target and temperature, plus memory and/or printout capa￾bilities. Dual- and multi-wavelength thermometry are used in applications where absolute accuracy is critical, and where the product is undergoing a physical or chemical change. Dual-wavelength thermometry in￾volves measuring the spectral energy at two different wavelengths. The target temperature can be read directly from the instrument if the emissivity has the same value at both wavelengths. The advantage of ratio measuring is that temperature readings are greatly independent of emissivity fluctuations and/or sight path obscurations. The technique is generally used for temperatures above incandescence (1300°F (700°C)), but measurements down to 400°F (200°C) are possible. Advantages of infrared detectors are that they are non-contacting, can be used to measure very high temperatures, and can be used to measure temperatures in hostile environments, provided visual access can be obtained. One disadvantage is that the surface emissivity at the temperature of interest must be known (this information is not always known). In addition, the device will average all of the temperatures in its field of view. If a target does not completely fill the field, the temperature of its background will contribute to the reading. If the target is not a perfect emitter, it will reflect infrared energy from other sources that can be detected by the device. 6.4.5.9 Calibration of temperature measurement devices The effectiveness of any temperature measuring equipment is dependent on its accuracy and its re￾peatability. As with other measuring equipment, temperature devices must be calibrated and periodically verified to maintain confidence that their indicated output is within a certain known tolerance to the true value. Calibration and verification of temperature devices is simple in concept and involves merely ex￾posing the device of interest and a reference device to the same temperature. Any deviation of outputs then can be corrected, in the case of calibration, or noted as in or out of tolerance, in the case of verifica￾tion. For the purposes of this document, calibration and verification will be considered together and will

MIL-HDBK-17-1F Volume 1,Chapter 6 Lamina,Laminate,and Special Form Characterization both be referred to as "calibration".General information on temperature measurement can be found in References 6.4.5.9(a)and (b). Temperature measurement devices are nearly always attached to a readout or control instrument of some type,which must also be calibrated.Often the instrument can be included with the probe and the assembly calibrated as a system.This is preferred because all components of the system are considered together,which leads to greater accuracy and can save considerable time.The user should refer to the specific instrument operations manual for its calibration requirements and procedures.Additionally.good information for temperature device calibration can be found in the following ASTM specifications: ASTM E220 Calibration of Thermocouples by Comparison Techniques(Reference 6.4.5.9(c)). ASTM E77-92 Standard Test Method for Inspection and Verification of Thermometers (Reference 6.4.5.9(d). ASTM E1502 Use of Freezing Point Cells for Reference Temperatures(Reference 6.4.5.9(e)). Note that though these standards are generally oriented toward a particular type of sensor,many of the practices can also be applied to other sensor types,particularly when applied in concert with the in- structions provided in the owner's manual for a given temperature sensor or system. The general calibration procedure for probes involves physically placing them in a known temperature environment together with a reference standard that should be traceable to National Institute of Standards and Technology(NIST)standards.The critical components of a probe calibration setup are shown in Fig- ure 6.4.5.9,and include: The "calibrator"(the device used to generate a known temperature). The reference standard probe-usually of the same type as the probe being calibrated. A readout device(typically a high resolution digital multimeter of 5%digit resolution or an indicator which provides scaling and cold junction compensation for the probe). An ice point reference (used to locate the open end of a thermocouple-T2-at the proper refer- ence temperature as discussed in Section 6.4.5.2).This is required when calibrating thermocou- ple type probes only,and provides the cold junction reference for thermocouple probes not oth- erwise compensated for the cold junction. The Calibrator Calibrators are the heating or cooling sources used to provide the thermal environment into which the instrument to be calibrated is placed.Calibrators must have outstanding temperature control capability, be extremely thermally stable,and free from temperature gradients.Circulating air furnaces are usually not sufficiently stable and exhibit relatively high thermal gradients.The calibrators most often used are specifically designed for probe calibration and are one of three types:block calibrators,circulating liquid baths,and fluidized powder baths. The block calibrator consists of an electrically powered unit that uniformly heats or cools a solid block of material (often copper)into which the probes are inserted.Block calibrators are clean and easy to maintain,but change temperature relatively slowly.It is also important that the probe fit snugly into the block,so thermal"wells"of many different sizes are often required when calibrating a variety of probes. Typical temperature ranges of block calibrators are-40F to 1200F(-40C to 648C). The circulating bath simply circulates a temperature-controlled fluid in a bath into which the probe is inserted.This type of calibrator is the least expensive of the three,but has a relatively limited tempera- ture range,typically-5 to 266F(-20 to 130C).More exotic and expensive baths can extend this range to-250to1170°F(-160to630°C). 6-24

MIL-HDBK-17-1F Volume 1, Chapter 6 Lamina, Laminate, and Special Form Characterization 6-24 both be referred to as “calibration”. General information on temperature measurement can be found in References 6.4.5.9(a) and (b). Temperature measurement devices are nearly always attached to a readout or control instrument of some type, which must also be calibrated. Often the instrument can be included with the probe and the assembly calibrated as a system. This is preferred because all components of the system are considered together, which leads to greater accuracy and can save considerable time. The user should refer to the specific instrument operations manual for its calibration requirements and procedures. Additionally, good information for temperature device calibration can be found in the following ASTM specifications: • ASTM E220 Calibration of Thermocouples by Comparison Techniques (Reference 6.4.5.9(c)). • ASTM E77-92 Standard Test Method for Inspection and Verification of Thermometers (Reference 6.4.5.9(d)). • ASTM E1502 Use of Freezing Point Cells for Reference Temperatures (Reference 6.4.5.9(e)). Note that though these standards are generally oriented toward a particular type of sensor, many of the practices can also be applied to other sensor types, particularly when applied in concert with the in￾structions provided in the owner’s manual for a given temperature sensor or system. The general calibration procedure for probes involves physically placing them in a known temperature environment together with a reference standard that should be traceable to National Institute of Standards and Technology (NIST) standards. The critical components of a probe calibration setup are shown in Fig￾ure 6.4.5.9, and include: • The “calibrator” (the device used to generate a known temperature). • The reference standard probe - usually of the same type as the probe being calibrated. • A readout device (typically a high resolution digital multimeter of 5½ digit resolution or an indicator which provides scaling and cold junction compensation for the probe). • An ice point reference (used to locate the open end of a thermocouple - T2 - at the proper refer￾ence temperature as discussed in Section 6.4.5.2). This is required when calibrating thermocou￾ple type probes only, and provides the cold junction reference for thermocouple probes not oth￾erwise compensated for the cold junction. The Calibrator Calibrators are the heating or cooling sources used to provide the thermal environment into which the instrument to be calibrated is placed. Calibrators must have outstanding temperature control capability, be extremely thermally stable, and free from temperature gradients. Circulating air furnaces are usually not sufficiently stable and exhibit relatively high thermal gradients. The calibrators most often used are specifically designed for probe calibration and are one of three types: block calibrators, circulating liquid baths, and fluidized powder baths. The block calibrator consists of an electrically powered unit that uniformly heats or cools a solid block of material (often copper) into which the probes are inserted. Block calibrators are clean and easy to maintain, but change temperature relatively slowly. It is also important that the probe fit snugly into the block, so thermal “wells” of many different sizes are often required when calibrating a variety of probes. Typical temperature ranges of block calibrators are -40°F to 1200°F (-40°C to 648°C). The circulating bath simply circulates a temperature-controlled fluid in a bath into which the probe is inserted. This type of calibrator is the least expensive of the three, but has a relatively limited tempera￾ture range, typically -5 to 266°F (-20 to 130°C). More exotic and expensive baths can extend this range to -250 to 1170°F (-160 to 630°C)

MIL-HDBK-17-1F Volume 1,Chapter 6 Lamina,Laminate,and Special Form Characterization 双XxXm DMM XX.XXXmV XXXX☒ CJ Compensated Readout XXX☒ ■ T/C Wire to Copper Wire Probe under Reference Connections test Probe Ice Point Reference NOTE:Each probe must have either a cold Junction(CJ)compensated Calibrator readout or a DMM device.Ice point reference and DMM components therefore only required for uncompensated output. FIGURE 6.4.5.9 Typical calibration setup. Fluidized powder bath calibrators use a gas,usually low-pressure air or nitrogen,to fluidize dry parti- cles of powder-typically aluminum oxide.These baths have excellent heat transfer characteristics and are clean and easier to maintain than a circulating bath.They also have a significantly higher tempera- ture range,though they are generally not capable of cryogenic temperatures.Common temperature ranges are from 122F to 1112F(50C to 600C).Extended range powder baths are available from-100 to1800°℉(-70to980°C). The Reference Standard Probe Reference standard probes are simply temperature probes that are calibrated and traceable to NIST. Obviously the calibration tolerance of the reference probe must be taken into account in the final toler- ance of the probe being calibrated.When calibrating a thermocouple probe without an attached readout instrument,it is important that the reference standard be of the same thermocouple type as the probe be- ing calibrated.This insures that both probes behave identically at the T2 ice point reference.When a sys- tem calibration is being performed,this is not essential because the instrument connected to the probe will provide independent cold junction compensation.Similarly,if the reference standard is not a stand- alone probe,but is a calibrated system consisting of a reference probe and a readout device that per- forms cold junction compensation,the probes need not be of the same type. All temperature measurement devices have limited temperature ranges over which their response is well behaved.It is therefore essential to verify that the reference standard probe is well behaved and cali- brated over the full range of its use. The Readout Device Depending on the type of reference standard used,and the probe being calibrated,the readout de- vice can vary considerably.If using reference standards or calibrating temperature probes without a read- out device that performs scaling and/or cold junction compensation,the recommended readout device is a 5%digit digital multimeter(DMM).This precision instrument allows the thermocouple output to be read 6-25

MIL-HDBK-17-1F Volume 1, Chapter 6 Lamina, Laminate, and Special Form Characterization 6-25 XXX.X° XXX.X° XX.XXXmV XX.XXXmV Ice Point Reference Calibrator CJ Compensated Readout DMM NOTE: Each probe must have either a cold Junction (CJ) compensated readout or a DMM device. Ice point reference and DMM components therefore only required for uncompensated output. Probe under test Reference Probe T/C Wire to Copper Wire Connections FIGURE 6.4.5.9 Typical calibration setup. Fluidized powder bath calibrators use a gas, usually low-pressure air or nitrogen, to fluidize dry parti￾cles of powder – typically aluminum oxide. These baths have excellent heat transfer characteristics and are clean and easier to maintain than a circulating bath. They also have a significantly higher tempera￾ture range, though they are generally not capable of cryogenic temperatures. Common temperature ranges are from 122°F to 1112°F (50°C to 600°C). Extended range powder baths are available from -100 to 1800°F (-70 to 980°C). The Reference Standard Probe Reference standard probes are simply temperature probes that are calibrated and traceable to NIST. Obviously the calibration tolerance of the reference probe must be taken into account in the final toler￾ance of the probe being calibrated. When calibrating a thermocouple probe without an attached readout instrument, it is important that the reference standard be of the same thermocouple type as the probe be￾ing calibrated. This insures that both probes behave identically at the T2 ice point reference. When a sys￾tem calibration is being performed, this is not essential because the instrument connected to the probe will provide independent cold junction compensation. Similarly, if the reference standard is not a stand￾alone probe, but is a calibrated system consisting of a reference probe and a readout device that per￾forms cold junction compensation, the probes need not be of the same type. All temperature measurement devices have limited temperature ranges over which their response is well behaved. It is therefore essential to verify that the reference standard probe is well behaved and cali￾brated over the full range of its use. The Readout Device Depending on the type of reference standard used, and the probe being calibrated, the readout de￾vice can vary considerably. If using reference standards or calibrating temperature probes without a read￾out device that performs scaling and/or cold junction compensation, the recommended readout device is a 5½ digit digital multimeter (DMM). This precision instrument allows the thermocouple output to be read