NIST Measurement Services:

Benjamin K. Tsai, Charles E. Gibson, Annageri V. Murthy, Edward A. Early,

David P. Dewitt, and Robert D. Saunders

U.S. Department of Commerce

Technology Administration

National Institute of Standards and Technology

1

Qt

500 H

NIST Special Publication 250-65

NIST MEASUREMENT SERVICES:

Heat-Flux Sensor Calibration

Benjamin K. Tsai, Charles E. Gibson, Annageri V. Murthy, Edward A. Early,

David P. Dewitt, and Robert D. Saunders

Optical Technology Division

Physics Laboratory

National Institute of Standards and Technology

Gaithersburg, MD 20899-0001

May 2004

U.S. DEPARTMENT OF COMMERCE

Donald L. Evans, Secretary

Technology Administration

Phillip J. Bond, Under Secretary for Technology

National Institute of Standards and Technology

Arden L. Bement, Director
National Institute of Standards and Technology Special Publication 250-65

Nat. Inst. Stand. Technol. Spec. Publ. 250-65, 37 Pages, (May 2004)

CODEN: NSPUE2

NIST PRINTING AND DUPLICATING OFFICE

GAITHERSBURG, MD: 2004
PREFACE

The calibration and related measurement services of the National Institute of Standards

and Technology are intended to assist the makers and users of precision measuring

instruments in achieving the highest possible levels of accuracy, quality, and

productivity. NIST offers over 300 different calibrations, special tests, and measurement

assurance services. These services allow customers to directly link their measurement

systems to measurement systems and standards maintained by NIST. These services are offered to the public and private organizations alike. They are described in NIST Special

Publication (SP) 250, NIST Calibration Services Users Guide.

The Users Guide is supplemented by a number of Special Publications (designated as the

"SP250 Series") that provide detailed descriptions of the important features of specific

NIST calibration services. These documents provide a description of the: (1)

specifications for the services; (2) design philosophy and theory; (3) NIST measurement

system; (4) NIST operational procedures; (5) assessment of the measurement uncertainty

including random and systematic errors and an error budget; and (6) internal quality

control procedures used by NIST. These documents will present more detail than can be

given in NIST calibration reports, or than is generally allowed in articles in scientific

journals. In the past, NIST has published such information in a variety of ways. This

series will make this type of information more readily available to the user.

This document, SP250-65 (2004), NIST Measurement Services: Heat-Flux Sensor

Calibrations is a new publication. It covers the calibration of heat-flux sensors (test

number 3510IC in SP250, NIST Calibration Services Users Guide). Inquiries

concerning the technical content of this document or the specifications for these services

should be directed to the author or to one of the technical contacts cited in SP250.

NIST welcomes suggestions on how publications such as this might be made more

usefiil. Suggestions are also welcome concerning the need for new calibrations services,

special tests, and measurement assurance programs.

John R. Rumble, Jr. Director

Measurement Services

Katharine B. Gebbie

Director

Physics Laboratory

iii
ABSTRACT

The Optical Technology Division at NIST is developing techniques to calibrate heat-flux sensors to meet the current calibration needs of U.S. science and industry. An outcome

of this effort is a calibration service offered now through NIST Cahbration Services to calibrate heat-flux sensors up to 50 kW/m"". The calibration, performed using the 25 mm

Variable-Temperature Blackbody as a broadband radiant source, transfers calibration

from a primary electrical substitution radiometer standard to the heat-flux sensor. In

contrast to other calibration methods using temperature traceability, the objective of this

calibration is to provide heat-flux traceability to NIST primary standards. This report

gives the calibration principle, the associated laboratory procedure, safety, and typical

calibration results of a Schmidt-Boelter type heat-flux sensor.

KEY WORDS: Blackbody, heat flux, sensor

iv
TABLE OF CONTENTS

Abstract iv

1. Introduction 1

2. Measurement principle 1

3. Traceability 2

4. Calibration technique 3

4. 1 25 mm Variable-Temperature Blackbody 3

4.2 Transfer Standard Radiometer 4

4.3 Radiometer Calibration 5

4.4 Reference Calibration Sensor 5

5. Calibration Procedures 8

5.1 Pre-Calibration inspection 8

5.2 Additional test equipment 8

5.3 Calibration 9

5.4 Post-Calibration inspection 9

5.5 Data reduction 10

5.6 Calibration report 10

6. Measurement uncertainty 10

6.1 Transfer standard 10

6.2 Blackbody temperature (VTBB) 10

6.3 Blackbody emissivity 1

1

6.4 Blackbody radiation - aperture uniformity 1

1

6.5 Alignment error (distance) 1

1

6.6 Alignment error (angular) 1

1

6.7 Radiometer aperture size 1

1

6.8 Radiometer/Sensor reading 13

6.9 Other sources 13

6.10 Combined uncertainty 14

References 1

5

Appendix A: Heat-flux sensor: Laboratory procedure manuals 16

Appendix B: Sample calibration report 22

Appendix C: Blackbody operation: Laboratory procedure manuals 32

Appendix D: How to request calibration services 38

V
LIST OF FIGURES

Figure 1 Transfer calibration and traceability 2

Figure 2 Schematic layout of the 25 mm Variable-Temperature Blackbody 3

Figure 3 Transfer standard Kendall radiometer layout 4

Figure 4 Schematic representation of a Schmidt-Boelter sensor 6

Figure 5 Typical calibration results on reference sensor in VTBB 7

Figure 6 Incremental change in configuration factor with distance 12

Figure 7 Ratio of peak to average irradiance at sensor/radiometer location 12

Figure 8 Standard deviation of the mean output for two sensor locations 13

Figure A1 ESR control unit front panel 17

Figure A2 ESR calibration [1] 21

LIST OF TABLES

Table 1 a Radiometer specification 4

Table lb Radiometer control unit specification 5

Table 2 Reference Schmidt-Boelter sensor specification 6

Table 3 Summary of linear regression results on reference sensor 8

Table 4 Heat-flux at sensor location for different blackbody temperatures 9

Table 5 Estimate of uncertainty in heat-flux sensor calibration [%] 14

vi
1. Introduction

The National Institute of Standards and Technology initiated a competence

program in the year 1995 to develop techniques for calibration of high heat-f1ux sensors. An outcome of the competence program is the capability to calibrate heat-flux sensors with traceability to the High Accuracy Cryogenic Radiometer. The current range of

calibration, performed with a 25 mm Variable-Temperature Blackbody (VTBB), is up to 50 kW/m^. The calibration technique [1] uses an electrical substitution radiometer (ESR)

as the transfer standard.

The calibration is now available to the user community through the NIST

Calibration Services. Several sensors calibrated so far show good repeatability of the

technique with an expanded uncertainty of 2 %, corresponding to a coverage factor of

A: = 2 or 95 % confidence level. This report gives a description of the equipment used in

the calibration, laboratory procedure currently in practice, and an evaluation of the

uncertainties in the measurement process.

2. Measurement principle

Radiant heat flux is essentially a radiometric quantity representing the broadband

irradiance or flux received per unit area by a surface. For a radiometer placed in front of

a radiant source, the governing measurement equation for the radiometer signal output

where x and y specify the location on the radiometer on which radiant flux is incident, 0

and specify the direction from which radiant flux is incident on the radiometer, A is the

wavelength, L is the radiance of the incident radiant flux, R is the responsivity of the

radiometer, and G is the amplifier gain. The integrals are performed over the entire area of the radiometer upon which radiant flux is incident, over all directions from which

radiant flux is emitted by the source and received by the radiometer, and over all wavelengths to which the radiometer is sensitive. Any temporal dependence is excluded

in Eq. (1) since heat flux measurements are typically performed under steady-state

conditions.

For a given range of directions for the source and radiometer, integration of Eq.

(1) over the angles yields

where E is the irradiance. Note that the integral over angles to obtain Eq. (2) depends on

both the size of the source and the field-of-view of the radiometer. Also, the incident

radiant flux at the reference plane of the radiometer is measured, not the absorbed flux.

Effects fi-om a window or the absorptance of the detector are included in the responsivity.

Integrating Eq. (2) over the area of the radiometer, assuming the responsivity is uniform over the area, yields

(F)is

V = G - ||jx<iv jjcos 6d0d(l) jdA L(x, y, 6, (f), X) R(x, y, 6, (j). A) , (1)

(2)

(3)

1
where A is the area of the radiometer over which radiant flux is incident and E is the

average irradiance. The average irradiance is used in Eq. (3) because in nearly all measurement situations the irradiance has a spatial distribution that is a maximum at the

center of the radiometer. Therefore, the average irradiance will depend upon the size of

the radiometer.

Finally, a typical radiometer used as a heat-flux sensor has a responsivity that is independent of wavelength, so Eq. (4) reduces to

(4)

where R is the average responsivity over wavelength. The product of the amplifier gain,

area, and the average responsivity is the quantity calibrated for heat-flux sensors.

3. Traceability

Heat-flux sensor calibrations are traceable to the primary detector standard for

radiometric measurements. However, because of the range of radiant powers between the

primary standard and the heat-flux sensor (microwatts to watts), the traceability chain

involves multiple steps, shown in Fig. 1

The primary detector standard is the High Accuracy Cryogenic Radiometer

(HACR) [2], which uses low-power lasers to calibrate the responsivity of primary trap

detectors. These primary trap detectors are used in turn in the Spectral Comparator

Facility (SCF) [3], a lamp-illuminated monochromator system, to calibrate the

responsivity of quantum efficient detectors (QED). The maximum radiant power for a QED is about 2 mW, which precludes its use to calibrate heat-flux sensors, for which the

radiant power is several orders of magnitude greater.

Detectors Sources

High Accuracy Cryogenic Radiometer (HACR)

Low-Power Lasers

Primary Trap Detectors

Quantum Efficient Detector (QED)

f

Spectral Calibration Facility

High-Power Lasers

Electncal Substitution Radiometer (ESR)

Heat-Flux Sensors (Gardon, Schmidt-Boelter)

Variable-Temperature Blackbody

Figure 1. Traceability of heat-flux sensor calibrations

2
A cavity-type ESR operating at room temperature is the transfer standard for heatflux sensor cahbrations. The QED is used to calibrate the radiant power of a high-power

krypton laser, which is then used to calibrate the responsivity of the ESR. The final step

in the traceability chain, described in detail in the following, transfers the calibration

from the ESR to the heat-flux sensor using the VTBB.

4 Heat-flux sensor calibration

4.1 Variable-Temperature Blackbody

The VTBB is a thermally insulated graphite tube cavity heated electrically.

Figure 2 shows a schematic layout of the blackbody and the test arrangement for

calibrating a typical heat-flux sensor. Direct resistance heating of the tube using large

AC currents at low voltages provides for quick heating and cooling. The heated tube

cavity diameter is 25 mm, and the heated section is 28.2 cm long with a center partition,

0.3 cm thick.

The water-cooled end caps of the heated tube connect directly to the heating

electrodes. The design provides a sharp temperature gradient between the end cap and

the graphite heater element, and a uniform temperature distribution along the cavitylength of the graphite tube. An optical pyrometer measures the blackbody temperature by

sensing radiation from one end of the furnace. A Proportional-Integral-Derivative (PID)

controller regulates the power supply to maintain the furnace temperature to within

±0.1 K of the set value. The maximum recommended operating temperature for the

blackbody is 2973 K.

With the standard extension installed and the sensor located 1.25 cm from the

exit, the distance between the sensor and the end of the heated section will be 17.4 cm. However, the maximum flux-level at this location is limited. With a shorter-extension

installed, the sensor location can be closer to the blackbody radiating-cavity resulting in

higher flux-levels. At a distance of 1.25 cm from the exit, the maximum flux-level is approximately 50 kW/m^. Away from the aperture, the irradiance decreases rapidly, and

is about 10 kW/m^ at a distance of 62.5 mm.

Optical

pyrometer

Extension

(not cooled)

Water-cooled end caps

Graphite tube cavity

Heated section

ESR

>

Extension Heat-flux

(not cooled) sensor

Aperture: 25 mm dia. Purge gas: Argon

Temperature: up to 2973 K

Heat-flux sensor: 50 kW/m2

Computer Power supply

Figure 2. Schematic layout of the VTBB

3
4.2 Transfer Standard Radiometer

The ESR transfer standard is a water-cooled Kendall radiometer [4]/ shown in

Fig. 3. The ESR absorbs the incident radiant flux almost completely because of the

blackened cavity walls and multiple reflections within the cavity. The equivalent

electrical power, measured by the current through a precision resistor, required to produce the same cavity temperature rise as the radiant flux, is the power of the radiant

flux. The maximum incident radiant power for the ESR is 4.2 W and the aperture area is

1 cm . The time constant (l/e) for a step change in irradiance is 6 s. For large changes in

irradiance, it is necessary to allow about 60 s for stabilization before taking

measurements [5]. The manufacturer stated uncertainty of this radiometer is 0.5 %, as determined by an experimental measurement of the Stefan-Boltzmann constant. Tables

la and lb give the radiometer and the control unit specification, respectively.

@@@@@

Figure 3. Transfer standard Kendall radiometer layout.

Table la. ESR transfer standard specifications

Type Kendall MK-IV, S/N 47601

Range 0.04 kW/m- to 42 kW/m'

Accuracy ± 0.5 % of reading ± 0.2 mW/cm'

Time constant 6 s (l/e)

Sensitivity > 10mV/(W/cm^)

View angle No view limiting aperture

Calibration heater 230 W, 150 mA maximum

Outer surface coating 0.005 mm pure gold plate

Mounting 5 mm metric machine screw

Cabling 4 m long, Bendix PT06A-14-19P

Size 5 1 mm diameter, 76 mm long

Weight 0.9 kg

manufactured by Technical Measurements Inc., La Canada, CA. Certain commercial equipment, instruments, or materials are

identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National

Institute of Standards and Technology, nor does it imply that the materials or equipment are necessarily the best available for the purpose.

4
Table lb. ESR transfer standard control unit specification

Kendall MK-I Radiometer Control Unit (Serial No. 17601)

Accuracy Absolute measurement uncertainty < ± 0.5 % full scale

Zero drift < ± 0. 1 % per month of full scale

Time constant <2 s(l/e)

Display ±39 999 counts normal range

Output: Analog ± 10V,±5mA

Output: Digital Buffered, stored, parallel BCD

Size 43 cm wide, 14 cm high, 46 cm deep

Weight 10 kg

4.3 ESR Calibration

The self-calibration feature of the ESR facilitates absolute measurements of the

incident irradiance within the stated experimental uncertainties. However, other

uncertainties related to cavity heating and long-term drift make it desirable to characterize the radiometer independently by comparison to a QED with a high-power

krypton laser [1]. The calibrations from three different sets of measurements of the ESR

showed a high degree of linearity with a regression factor of 0.999. The calibration

constant agreed to within 1 % between two tests conducted a year apart. From these

tests, the relation between the corrected (^c) and the indicated {E\) ESR readings is obtained as [Appendix A]

=0.9855£, , (5)

All of the calibrations performed with the VTBB use this relation to provide

consistency and establish the long-term repeatability of the calibration technique. The

uncertainty associated with the ESR calibration is of Type-B [7] in determining the total measurement uncertainty.

4.4 Reference Sensor Calibration

The heat-flux sensor calibration procedure is repeatable as demonstrated fi-om

periodic calibrations of a reference sensor. This reference sensor calibration, performed

before calibrating a customer-supplied sensor, ensures that the long-term stability of the

calibration procedure is monitored. The Schmidt-Boelter type reference sensor, shown in

Fig. 4, works on the principle of axial one-dimensional heat flow. It measures the

temperature difference across a thin, thermally insulating layer to determine the incident

heat flux. Due to the axial flow of heat, the temperature distribution across the sensing

surface is uniform. The maximum body temperature is limited to about 200 °C when the sensor is not water-cooled. For applications involving continuous use, the sensor body is water-cooled. Reference [6] gives a detailed description of Schmidt-Boelter sensor

operation.

Table 2 hsts the specifications of the Schmidt-Boelter reference sensor. The body

diameter and length are 5 mm and 9 mm, respectively. The design heat-flux value of

110 kwW is representative of the calibration range of interest. A number of calibrations

of this sensor performed over a period of time cover different locations firom the

5
blackbody aperture, and different blackbody temperature ranges,

results of the calibration for incident heat flux of up to 50 kW/m".

Figure 5 shows the

Heat flux

JfJUL.

Black

paint

Temperature

distribution

•Wafer

Copper

leads

Heat sink

Figure 4. Schematic representation of a Schmidt-Boelter sensor

Table 2. Reference Schmidt-Boelter sensor specification

Type Schmidt-Boelter

Manufacturer Medtherm Corp.

Model 12-10-0.35-75-20841J

Serial Number #94761

Design flux llOkW/mBody diameter 5 mm

Body length 9 mm

Thermocouple Shielded copper wires

Body not water-cooled

1

CO

-9 X= 12.5 mm (7/23/96) -m X = 62.5mm (7/31/96) X= 12.5 mm (5/25/97) X= 12.5 mm (5/30/97)

-<B X= 12.5 mm (8/19/97)

-4B X = 12.5 mm (8/21/97) ^

JP Blackbody [~^^

E

Sensor

10 20 30

Heat flux [kW/m2]

40 50

Figure 5. Typical calibration results on the reference sensor.

6
All of the calibrations show a linear response of the sensor, with regression

factors close to unity. Table 3 summarizes the results of the sensor responsivity

calculations from linear regression analysis of the measured data. The responsivity

values from several calibrations agree to within ± 0.7 % of the mean value. The good

repeatability of the data supports the long-term stability of the transfer standard ESR, the

reference sensor, and validates the VTBB transfer calibration technique. The standard

deviation of responsivity determined from these measurements is an additional source of

uncertainty when determining the total uncertainty of other calibrated heat-flux sensors.

Table 3. Summary of linear regression results on the reference sensor

Schmidt-Boelter Sensor (N1ST): #94761, 12-10-0.35-75-20841J

Test Distance Intercept Responsivit\'

No. Date X mm kW/m^ mV/(kW/m^) Deviation %

1 23-Jul-96 12.5 0.0018 0.1189 -0.18

2 31-Jul-96 62.5 -0.0687 0.1184 -0.59

3 25-Apr-97 12.5 0.0608 0.1190 -0.04

4 30-Apr-97 12.5 0.0186 0.1181 -0.83

5 19-Aug-97 12.5 0.0077 0.1191 0.06

6 21-Aug-97 12.5 0.0202 0.1197 0.50

7 9-NOV-97 12.5 0.1003 0.1200 0.76

8 ll-Nov-97 140 -0.0186 0.1180 -0.92

9 2-Jun-98 12.5 0.1348 0.1189 -0.16

10 16-Jul-98 12.5 0.0318 0.1199 0.71

11 17-Jul-98 62.5 0.0053 0.1187 -0.31

12 27-May-98 12.5 0.1149 0.1188 -0.27

13 29-May-98 12.5 0.2526 0.1183 -0.62

14 9-Jul-OO 12.5 -0.0644 0.1201 0.86

18 22-Jul-Ol 12.5 0.0300 0.1186 -0.38

19 16-Aug-Ol 12.5 0.0364 0.1183 -0.62

20 5-Nov-Ol 12.5 0.0374 0.1211 1.70

21 6-Nov-Ol 12.5 0.0472 0.1198 0.60

22 18-Aug-02 12.5 -0.0006 0.1187 -0.27

Arithmetic mean 0.0393 0.1191 0.00

Standard De\1ation 0.0732 0.0082 0.69

Standard Error 0.0168 0.0019 0.16

5. Calibration Procedures

The following specifies the stepwise procedure for calibrating heat-flux sensors with reference to the transfer standard radiometer using the VTBB.

7
5.1 Pre-Calibration inspection

The continuity of the sensor signal leads is checked and the value of the

resistance, using a multi-meter, is recorded. The condition of the high absorptance

coating on the sensor surface is inspected. If the conditions indicate the need for

repainting, the customer is informed. The surface is not repainted at NIST.

5.2 Additional test equipment

Heat-flux sensors have a wide range of configurations. Standard mounting blocks

and sensor holders are readily available for mounting the 25 mm diameter Gardon and

5 mm diameter Schmidt-Boelter sensors. However, some sensors may require special

mounting arrangement. If so, a suitable accessory is designed for fabrication in advance

of the calibration. The cooling requirements for the sensor, and the need for any special

instruments like amplifiers, thermometers etc., are checked.

5.3 Calibration

Appendices A and B detail the heat-flux sensor calibration procedure. The

reference standard radiometer (ESR) requires self-calibration prior to testing. Appendix

A describes the self-calibration procedure. The self-calibration, at a radiant power of

approximately 920 mW, is necessary to be consistent with the radiometer settings during

calibration and use. Self-calibration at other radiant powers within the range of the

radiometer is acceptable as long as the instrument settings during calibration and use are

identical. Appendix B describes the heat-flux sensor calibration procedure at about

8 to 10 heat flux levels covering the calibration range. Table 4 shows the required

temperature settings of the VTBB and corresponding heat-flux level at the sensor, for

different locations of the sensor from the blackbody aperture.

Table 4. Heat-flux values at sensor location for different blackbody temperatures

X= 12.5 mm X= 62.5 mm X= 140 mm

Temperature Heat-flux Temperature Heat-flux Temperature Heat-flux

[K] [kW/m'] [Kl [kW/m^] [K] [kW/m^l

1573 8.84 1823 5.09 1073 0.32

1773 13.07 1963 7.43 1573 1.30

1973 18.91 2108 9.72 1973 2.99

2123 24.19 2233 11.91 2273 5.11

2273 30.88 2373 14.94 2473 7.04

2273 30.91 2573 20.38 2573 8.21

2373 36.19 2773 27.08 2673 9.52

2453 41.17

2553 47.31

2653 54.81

X: Distance from blackbody aperture to sensor location

The heat-flux values listed are approximate and are useful in deciding the

8
optimum sensor location from the blackbody aperture to cover a desired calibration

range. The actual heat flux values may vary over the long term because of aging of the

graphite heating element and other factors. However, this variation will have no effect on

the actual calibration. The transfer standard radiometer measurements give the actual

heat flux values. Prior to calibrating the test sensor, it is desirable to perform a

calibration on the reference Schmidt-Boelter sensor described in Sec. 4.4.

5.4 Post-Calibration inspection

The heat-flux sensor is removed from the test installation after disconnecting the

signal lead, thermocouple lead, and cooling water. The signal lead continuity and the

resistance are checked, as well as the condition of the high absorptance coating to ensure

that it did not changed during the calibration process.

5.5 Data reduction

Appendix C gives the data reduction procedure. An EXCEL spreadsheet or other

standard statistical software may be used. The measured heat flux is calculated fi-om the

measurement equation,

V -V E.=-~, (6)

where is the measured sensor signal in V or mV, is the measured dark signal of the sensor in V or mV, and S is the measured responsivity of the heat-flux sensor expressed

2 2 in mV/(W/cm ) or mV/(kW/m ). The regression curve fit for the data is generally linear

with regression factors close to unity. In some cases, a small degree of non-linearity may

appear at low heat flux levels, when calibrating with the sensor located close to the

blackbody aperture. This non-linear effect is due to argon purge-gas flow effects, and

reduces with increasing heat flux. The calculated responsivity depends largely on the

readings at high heat flux levels.

5.6 Calibration report

A calibration report is prepared as per the standard format, shown in Appendix D,

including any special comments specific to the calibration and measurement

uncertainties.

6. Measurement uncertainty

The measurement uncertainty evaluation follows the procedure described in

reference [7]. The individual uncertainty at each stage of the calibration is either of

Type-A, evaluated using statistical methods, or Type-B, evaluated by other means". The

combined uncertainty is the root-sum-square of the individual uncertainty values. In the

transfer technique calibration of heat-flux sensors, the measurement uncertainties accrue

at two different stages. First, the uncertainty associated with the calibration of the

transfer standard radiometer; and secondly, the uncertainty arising while calibrating the

heat-flux sensor with the VTBB.

^ Previous measurement data, experience, manufacturer's specification, other sources of data

9
6.1 Transfer standard radiometer

The uncertainty associated with the transfer standard radiometer caHbration,

discussed in Sees. 3 and 4.3, is a Type-B uncertainty and estimated to be 0.6 %.

6.2 VTBB temperature

The absolute temperature of the VTBB has no influence on the transfer technique

calibration because the heat flux is determined independently from the radiometer

measurements. It is only necessary that the blackbody temperature be stable over the

time interval of the radiometer and test sensor measurements. The VTBB has a longterm stability within ±0.1 K of the set temperature. The corresponding uncertainty in the

radiant heat flux is 0.01 % at 1000 K and 0.004 % at 2773 K. This is negligible compared

to the other uncertainties and can be ignored.

6.3 VTBB emissivity

The estimated emissivity of the VTBB is 0.99. However, the blackbody

emissivity has no influence on the transfer calibration. Higher emissivity values result in

realizing higher heat flux levels at the sensor surface for a given operating temperature.

6.4 VTBB radiation - aperture uniformity

The uniformity of radiation from the VTBB aperture has no major influence on

the calibration because of identical effects on both the transfer standard and the test sensor. However, even with a uniformly radiating aperture, the irradiance distribution at the sensor location may not be uniform. This non-uniform distribution may require a

correction to the measured responsivity of the sensor, as detailed in Sec. 6.7.

6.5 Alignment error (distance)

The location of the effective aperture of the VTBB is close to the heated end,

about 8.5 cm inside the blackbody aperture with the short extension piece installed. The

test sensor and the transfer standard radiometer are at a fixed distance from the blackbody

aperture. Assuming a maximum error of about 0.2 mm in the location of the transfer

standard radiometer and the sensor with respect to the reference plane, the corresponding

uncertainty values will be 0.2 %, 0.14 % and 0.09 % at sensor locations corresponding to 12.7 mm, 62.5 mm, and 140 mm from the blackbody aperture, respectively. The

uncertainty in the longitudinal location of the sensor translates into a corresponding

change in the configuration factor (Cfa) between the radiating aperture and the sensor. Figure 6 shows the relative change in the configuration factor with respect to location of

the sensor from the aperture [8]. At large distances, the irradiance varies inversely as the

square of the distance from the aperture. Hence, the uncertainty in irradiance at the sensor will be approximately two times that due to positioning uncertainty. The

corresponding uncertainty values for the irradiance are 0.4 %, 0.3 % and 0.2 % at sensor

locations of 12.7 mm, 62.5 mm, and 140 mm, respectively.

6.6 Alignment error (angular)

The errors due to angular misalignment vary as the cosine of the angle. Assuming

a maximum misalignment of about 2°, the corresponding uncertainty will be 0.06 %.

10
0

-0.5

6hlh

-1.5

-2.00 2 4 6 8 10

hIb

Figure 6. Incremental change in configuration factor with distance [8]

6.7 Radiometer aperture size

The areas on which radiant flux is incident on the transfer standard radiometer

and the test sensor are different, and the heat-flux distribution in the test plane is not

uniform. The distribution is a maximum at the center, and decreases away from the

center. The sensitive area of the heat-flux sensor is generally small, and responds to the

peak of the distribution. However, the aperture size of the transfer standard radiometer is much larger. Hence, the response of the transfer standard radiometer will be proportional

to the average irradiance over the distribution.

Due to the averaging of the distribution over the aperture area, a correction to the radiometer measurement is necessary to determine the peak value of the distribution

from the average reading. This peak value corresponds to the radiation incident on the sensor surface. The correction is a function of the sensor location from the blackbody

aperture [8]. Figure 7 shows the calculated correction for different sensor dimensions as a function of sensor location fi-om the blackbody aperture.

The correction factor is unity when the sensor is located at the aperture plane

because of the uniform distribution. The correction peaks at a distance approximately

equal to the radius of the aperture, and decreases asymptotically to unity at large

distances. The correction is a strong function of the ratio of the sensor to the aperture

radii. For the VTBB transfer calibration setup, a conservative value of the radiometeraperture to sensor diameter ratio is about 0.44. The corresponding correction is less than

0.3 % of the measured radiometer reading. The correction increases rapidly when

moving closer to the blackbody aperture. The uncertainty involved in evaluating this

correction arises mainly fi-om the difficulty of defining the exact position of the effective

blackbody aperture. However, even with an uncertainty of about 5 % in the effective

11
location, the corresponding uncertainty in the correction will be less than 0.05 %.

1.08

0 2 4 6 8 10

hib

Figure 7. Ratio of peak to average irradiance at sensor location [8]

6.8 Radiometer/Sensor reading

The averaging times for the sensor and the radiometer measurements varies from

10 s to 60 s depending on the heat-flux level. If the sensors are water-cooled, longer

averaging times are feasible. Figure 8 shows a typical variation of standard deviation of

the mean (standard error) of the sensor output at two locations from the blackbody. The

uncertainty will be a maximum of about 0.2 %, and will be much less at heat-flux levels

greater than 10 kW/m^.

0.6 r

Heat flux kW/m^

12
Figure 8. Standard deviation of the mean output for two sensor locations [1]

6.9 Other sources The VTBB uses low-velocity argon gas flow to purge the cavity continuously

during operation. The average exit-flow velocity is about 0.08 m/s. When the sensor is close to the cavity-exit, the low velocity jet impinging the sensor surface causes changes

in the local heat transfer. This influence becomes smaller away from the exit because of

jet spreading effects. The good agreement in calibrations obtained for different sensor

distances from the blackbody suggests that the purge gas effect is not significant, and is within other experimental uncertainties. The agreement also suggests that the sensor's

high-absorptance is gray because of different blackbody temperature ranges used to obtain the same heat flux level at the sensor. The calibration of a heat-flux sensor over a period of time will show statistical

variations because of experimental conditions that are difficult to control. Therefore, an

uncertainty that indirectly accounts for purge-gas as well as other effects, based on longterm repeatability, is necessary. Several repeat measurements on the same reference sensor give a standard uncertainty value of 0.7 % for repeatability.

6.10 Combined uncertainty

Table 6 lists the individual uncertainties for different sources. The root-sumsquare of individual uncertainties gives the combined uncertainty value Wc. The relative

expanded uncertainty U, corresponding to a coverage factor of k =2, is about 2.1 %.

Table 5. Estimate of uncertainties in heat-flux sensor calibration [%]

(Heat-flux range 10 kW/m^ to 50 kW/m^)

Uncertainty Source Type Uncertainty

1. Transfer standard ESR (previous calibration) B 0.60

2. Blackbody temperature B O.Ol

3. Blackbody emissivity B < 0.001

4. Blackbody aperture - radiation uniformity B < 0.001

5. Alignment (distance) B 0.40

6. Alignment (angular) B 0.06

7. Radiometer aperture size B 0.05

8. Signal output: Radiometer A 0.20

Sensor A 0.20

9. Other sources: purge-gas, repeat tests A 0.70

lO.Relative expanded uncertainty {U = kuc) k = 2 2.1

13
References

1. A. V. Murthy and B. K. Tsai, "Transfer calibration of heat flux sensors at NIST,"

HTD-Vol. 345, ASME proceedings ofthe National Heat Transfer Conference, Edited

by D. Kaminski, A. M. Smitli and T. F. Smith, 7, 81-88 (1997).

2. T. T. Gentile, J. M. Houston, J. E. Hardis, C. L. Cromer, and A. C. Parr, "The NIST

high accuracy cryogenic radiometer," ^/7/>/. Optics 35, 1056-1068 (1996).

3. T. C. Larason, S. S. Bruce, and A. C. Parr, "NIST Measurement Services:

Spectroradiometric Detector Measurements: Part I - Ultraviolet Detectors and Part II - Visible and Near-Infrared Detectors," NIST Special Publication 250-41 (1998).

4. J. M. Kendall, Sr., and C. M. Berdahl, "Two blackbody radiometers of high

accuracy,"^/?/?/. Optics 9, 1082-1091 (1970).

5. Instruction Manual for Kendall Radiometer System - Radiometer Model No. MK-FV,

Serial No. 47601; Control Unit Model No. MK-I, Serial No. 17601; by Technical

Measurements Inc., La Canada, CA 91011.

6. Kidd, C. T., and Nelson, C. G., "How the Schmidt-Boelter gage really works,"

Proceedings of the 4f' International Instrumentation Symposium, pp. 347-368

(1995).

7. B. N. Taylor, and C. E. Kuyatt, "Guidelines for evaluating and expressing uncertainty on NIST measurement results," NIST Technical Note, \191 (1994).

8. A. V. Murthy, B. K. Tsai, and R. D. Saunders, "Aperture proximity effects in high

heat flux sensors calibration," J. Res. Natl. Inst. Stand. Technol, 103 (6), 621-624

(1998).

14
Appendix A

Heat-flux sensor: Laboratory procedure manual

HFMLPl: Kendall Radiometer Operating Procedure

HFMLP2: Heat-Flux Sensor Calibration Procedure

HFMLP3: Data reduction procedure

15
Optical Technology Division (844)

Heat-flux Measurements Laboratory Procedure

Kendall Radiometer Operating Procedure

Page 1 of 2

Written by: Murthy Annageri Procedure: HFMLPl

Approved by: Date:

Revised by: Date:

Kendall Radiometer Operating Procedure

Figure Al . ESR control unit front panel

1. Radiometer/Controller set-up

a. Radiometer controller power-switch in off-position

b. Connect radiometer Bendix cable to controller, & controller power cable to mains

c. Cover the radiometer front end with the cap

d. Connect the cooling water-pump outlet to the radiometer inlet

e. Connect cooling water-pump inlet & the radiometer outlet to the coolant reservoir

f. Adjust the dial on the pump flow-controller to a flow-rate of 0.5 L/m or higher

g. Switch-on radiometer controller power

h. Allow about 20 min for stabilization

2. Digital voltmeter check-out (as and when needed)

a. Set switch "S 1 " to "OPERATE"

b. Connect a Standard voltage source to the BNC input connector

c. Set switch "S2" to "ZERO" position

d. Turn DVM's "ZERO" adjust potentiometer to set the read-out to zero

e. Set switch "S2" to "SCALE" position

f. Adjust DVM's "SCALE" potentiometer to read the standard voltage source value.

continued

16
Optical Technology Division (844)

Heat-flux Measurements Laboratory Procedure

Kendall Radiometer Operating Procedure

Page 2 of 2

Written by: Murthy Annageri Procedure: HFMLPl

Approved by: Date:

Revised by: Date:

3. Dark signal

a. Set both the switches "S 1 " and "S2" to "OPERATE"

b. Allow the unit to stabilize for about 20 min

c. The steady read-out gives the dark-signal value

d. Turn the "TARE(R1 7)" adjustment potentiometer to set the read-out to 0.000

4. Radiometer self-calibration & Operation (See note)

a. Set switch "S

1 " to "SCALE" position, and set switch "S2" to "VOLTS" position

b. Turn potentiometer "HEATER-R16" to adjust to the desired voltage

c. Set switch "S2" to "VOLTS" position: Note the voltage "V" on the meter

d. Set switch "S2" to "CURRENT" position: Note the heater current (I) in mA

e. Calculate electrical power (Pc) = V (Volts) x / (mA) x Cf (=0.9925)

[Cf is the radiometer aperture area (cm"). For the radiometer in use Cf = 0.9925]

f. Set switch "S2" to "OPERATE" position

g. Allow the read-out to stabilize: Note the indicated power P\ on the meter

h. UP, 7^ Pc, adjust potentiometer "SCALE(R1 8)" to set read-out P„ to P^

i. Set both the switches "S

1 " and "S2" to "OPERATE" position.

Note: The radiometer self-calibration is at a power level ~ 920 mW corresponding to the calibration power level used in the laser facility. The radiometer calibration gives the actual heat flux value.

17
Optical Technology Division (844)

Heat-flux Measurements Laboratory Procedure

Heat-flux Sensor Calibration Procedure

Page 1 of 2

Written by: Murthy Annageri Procedure: HFMLP2

Approved by: Date:

Revised by: Date:

Heat-flux Sensor Calibration Procedure

TO

COLLISION

1. Calibration set-up

a. Remove the standard graphite tube extension on the viewing end of the VTBB

and replace it with the short extension.

b. Locate/align the reference ESR and the test-sensor at a fixed distance fi"om the

VTBB exit using standard gage blocks^

c. Note down position values for the Aerotech-stage corresponding to the ESR

(Station-1) and the test sensor (Station-2) location when aligned with VTBB axis

d. Identify another position (Station-3) away from the ESR and the sensor, to station

VTBB while being heated or cooled

e. Connect cooling water pump to the ESR and set the flow-rate to 0.5 L/m or higher

f. If the test-sensor is water-cooled, make appropriate cooling arrangements as per

manufacturer's specification

g. If the test-sensor has body-temperature thermocouple, connect the leads to Fluke

thermometer to monitor body temperature during testing

h. Connect analog output of the control unit to Channel-1 of the HP multi-meter

3457A

i. Connect the sensor signal leads (or the amplifier output) to Channel-2 of the HP

multi-meter 345 7

j . Check connections, signal-polarity and instrument-cooling for proper functioning

k. Record dark signals for the ESR and test sensor for about 60 s.

continued

Recommended location of the sensor from the blackbody exit is 12.5 mm, 62.5 mm and 140 mm for calibration up to about 50 kW/m^, 25 kW/m"^ and 10.0 kW/m^, respectively.

18
Optical Technology Division (844)

Heat-ilux Measurements Laboratory Procedure

Heat-flux Sensor Calibration Procedure

Page 2 of 2

Wntten by: Murthy Annagen Procedure: HFMLP2

Approved by: Date:

Revised by: Date:

2. Calibration Measurements

BRIGHT SOURCE

BURN

ELECTROCUTION

IMPORTANT

Prior to calibration of test-sensor, perform a checli out calibration on the reference sensor

a. Record laboratory temperature and humidity

b. Locate the VTBB at Station-3

c. Turn on the VTBB as per procedure in manual RTMLPl 1.1

d. Set the desired temperature(Table 4) and allow the VTBB to stabilize

e. Move the VTBB in front of the ESR located at Station-1

f. Allow about 60 seconds for the ESR readings to stabilize

g. Record ESR output for about 20 s to 60 s depending on the heat-flux level"^'^ h. Move the VTBB to Station-2 in front of the test sensor

i. If the sensors are not water-cooled, go to Step (1)

j. Water-cooled sensors: Record output signal for about the same duration as ESR

k. Go to Step (m)

1. Data taking duration: Limited by the sensor body-temperature increase with time.

Monitor body-temperature-rise when exposing to radiant heat flux. Limit

exposure time to about 1 0 s or less at high heat flux levels.

m. Move the VTBB to Station-3

n. Set VTBB temperature to the next value of heat flux and wait till stabilization

o. Follow Steps (e) to (m) till completion of calibration range

p. At the end of calibration, move the VTBB to Station-3

q. Shut down blackbody following standard procedure in the Laboratory

r. Remove the radiometer and the test sensor from the setup. Inspect to ensure the

instruments are in good condition

> 60 s at heat-flux of 10 kWW, 20 s or lower at 50 kW/m^ when the distance between the blackbody and

the sensor is 12.5 mm. About 10 s to 20 s when the distance is 62.5 mm or higher

^ Note: Use a suitable file name to store the radiometer and sensor output data for later analysis

19
Optical Technology Division (844)

Heat-flux Measurements Laboratory Procedure

Heat-flux Sensor Calibration Data Reduction Procedure

Page 1 of 1 Written by: Murthy Annageri Procedure: HFMLP3

Approved by: Date:

Revised by: Date:

Data reduction procedure

1. Calculate the mean value of the radiometer output (Ei) in W/cm", and the test-sensor

output (V) from the data for each temperature setting of the blackbody.

2. Subtract the dark signals from the mean values calculated in Step-1. For calibration

at high heat flux levels, the dark signals are small compared to the signal levels.

3. Calculate statistical quantities of interest such as standard deviation of the mean, from

the radiometer and sensor output readings to calculate measurement uncertainty.

4. Convert the indicated radiometer mean value (Ei) to corrected radiometer power (Ec)

by using the relation by Ec = 0.9855 x Ei [See Fig. A2]

5. Express sensor output in mV

6. Perform a linear regression analysis for the heat-flux (Ec) and the sensor output (mV)

The slope of the linear regression gives the responsivity of the sensor in mV/(W/cm^)

7. Plot the calibration data as shown in Fig. 5 for the reference Schmidt-Boelter sensor.

8. Calculate measurement uncertainty in the calibration as listed in TabIe-5

Note: For calculation of mean value, standard deviation, and standard error, use a spreadsheet or other

statistical software.

2.5

2.0

i

(DO

Q. 10

OoV.i_oO

0.5

0 0.5 1.0 1.5 2.0 2.5

Indicated power E, [W]

Figure A2. ESR calibration [1]

20
Appendix B

Heat-flux sensor - Sample Calibration Report

21
REPORT OF CALIBRATION

3 5070S Special Testol'Ifcat Flux Sensor

for

HF Sensore. Model # HFT-X-OOOOOJ

Serial # 00000. 1 1 11 {. 22222. 33.333, 44444, and 55555

Submitted by:

Radiometric Systems, Inc.

.4ttn.; John Doe

123 Calibration Blvd. West

Measui ement Cit>-, MD 00000-0000

(See your purchase order 0446N, dated .Tune 10, 1999)

1. l>escription of Calibnition Itoni{»j)

Six Schmidl-Boelter ivpe heal llux sensors were calibrated by the National Institute of Standards md Tecltnolog\ (XIST) from 0 VV cm* to 5 W cm'. The Schmidl-Boelter sensor measures the temperature ditTerence between two parallel surlaces normal to the incident heat flux. ITie tiiermopik- concept is used to mak£ accurate measurement of tlie temperature gradient across a thin thennaliy imulaling material to determine the heat flux rate to the sensor surface, Tlie test sensors were of miniature typo (4 mm body diameter), and the design total (radiant and

convective) heat flux range is 5 W/cm* ). .Appendix A lists major .specifications ofthe seasors.

Sensor * 1 1 1 1 1 showed an open circuit for the body temperature thermocouple leads. Tliis sensor was calibrated without monitoring tlie sensor body temperature.

2. Description of Calibration

The heat flux sensors were calibrated using the 25-nun Variable Temperature Blackbody

( VTBB) as a transfer source. A room-temperature water-cooled electrical sub.stitution radiometer (ESR) v>as used as a transfer stiindard. The ESR is a Kendall radiometer model Mmk

IV self-calibrated at a power le\el of 920 mW. Tlie cooling water tlow rate and temperature were 0.9 L m and 24 "C, respeetiveh-.

Laborator\ Environment

Temperature: 23 °C ± 2 "C

Relative Humiditv; 50 % ± 3 "a

Calibration Date: .^gust 19, 1999 NISTTestNo.: 844.000000-99 SAMPLE

Page 1 of

9

22
liEPORT OF C:ALIBR.\TI0.\ Manufacturer HF Sensors

3 5070S Special Test of Heat Flux Sensor Model : HVY-X-mm}

Radiometric Systems Inc. Serial 00000, 11111. 22222. 33333. 444444. 55555

Appendix A: Details of Test Schmidt-Boeltcr Sensors

Manufacturer | HF Sensors Corporation

Number of Gagfs |_6

1 Gage specification j HFT-X-OOOOOJ

' Gage identification I Serial ^ 00000. 1 11 11. 22222. 33333, 44444 and 55555

Design Heal Flu\ | 5 W/cm'

Iktdv diameter j_4 ik>dy length ]_8

\ Sensor area I 1 mm x 1 mm

I Thennopile lead wires \ 32 AWG, Stranded copper with Teflon insulation twisted

I

\ pair. (White positive. Black negative)

I Body-temperature themiocoupic ; Type J (Iron-Constantan), 30 AWG

iji^teisunum body-temperature j 204 °C (400 °F)

Appendix B: Schmidt-Boelter Sensors Calibration in VTBB

I

I ^ . ^ - ^ ^ j VTBB i Thermogage Furnace

[_ _ i 25 mm diameter cavity (with short extension piece)

j Temperature range j 1300 °C to 2330 °C

j Transfer standard i Electrical Substitution Radiometer, Mark I\"

I Serial No.: 47601, Control Unit Serial No.: 1 7601

1 Manufacturer; TMI. La Canada. C.A

! Self^calibration Power Level: 920 mW

Stmsor location j On the VTBB cavity axis (1.27 cm Irom the exit)

f Located using a gage block.

: Distance from aperture: 10.7 cm

Calibration type ; For incident flux

j Up to about 5.0 W-cm" at the sensor surface.

1 Measured ESR reading used for transferring heat flu,x Bodv temperature i Monitored asing a Fluke tliermometer

I Otiier accessories J Cooling water flow rale for ESR: 0.9 L min

I Cooling water temperature: 24 °C

j ESR and Seixsor tliermopile outputs acquired using a

i HP3857.\ Digital \'oltmetcr triggered by Pentium computer.

SAMPLE

CaObration Date: .\ugust 19, 1999 NIST Test No.: 844 000000-99 Page 9 of 9

23
REPORT OF C;ALIBllATION Manufacturer HF Sensors

3 5070S S{ieeia] Test of Heat Fkix Sensor Model: HFl -X-000(X)J

Rjidiometric Systems Inc. Serial if: 00000, 11111. 22222, 33333. 444444. 55555

The sensors were mounted on a holder4ieal-sink for purposes of testing. 'Ilie ESR and the sensors were located at a fixed distance from the X'TBB exit using a stand.ird gage block ( 1.27 cm thick): corresponding to a distance of 10.7 cm from the end of the blackbod\' heated regiwt.

Tlic variation in the heat flux level at tlie ESR .sensor location was obtained by operating tlie VTOB at diiferent temperatures ni the range 1573 K to 2603 K.

The output of tlie ESR (W/cm*) and die sensors (mY) were recorded by positioning tlie VTBB,

after stabilisation of the set temperature, in front of the in.struments. .Vppendi.K B gives details of

the various parameters re!e\ ant to this calibration. Tlie ESR readings were recorded after about 60 s exposure to the radiant heal lliix to account for the long time-constant. The Scliniidl-Boelier sensors outputs were recorded for about 20 s to 40 s depending on the heal tlux level. Tlie sensor body-temperalure wavS monitored using a Fluke thermometer during exposure to the radiant flux, llie maximum rise in the gage body temperature was less Ihiui 20 K at the highest

heat Ilux level.

Before calibrating the test sensors, a reference Sehmidl-Boelter type sensor wa.s calibrated. This

reference sensor is frequently calibrated to monitor the long-term repeatabililv of the calibration procedure. Tlie measured responsivity from the check calibration agreed \\ ith the mean of

previous calibrations within 1.0 "'a

3. Results of Calibration

Tables la and lb give the measured output of the sensors for different heat flux levels at tlie sensor surface. Over the heal fiux range tested, tlie outputs of all the six sensors increased

linearly with increasing heat flux. Linear curve fit to the test data showed the calculated regression factor was 1.000 for all the sensors. Figures la and lb show the results of calibration along with the linear regression analysis to the measured data. The responsi\it\' and scale factor values of the sensors calculated f rom the linear regression are given below. Tlie responsivity is detenniaed from die slope of llie cun e. The scale factor represents the inverse of tlie responsivity value.

Serial # Responsivity Scale factor [mV/{W/cra5} {(W/cm^)/mV] !

1 00000 3.084 0.324 !

1 mil 2.985 0.335 i

i 22222 2.924 0.342 !

! 33333 3.540 0.282 i

'i 4-1444 3.612 a277 I

1 55555 3.206 0.312 [

SAMPLE

Calibration Date: August 19, 1999 NIST Test No.: 844/000000-99 Page 2 of 9

24
REPORT OF C ALIBIMTION

35070S Special Test of Heal Flux Sensor

Rftdiometric Svsteins Inc.

Manufaclurcr: HF Seasors Model: HFT-X-OOOOOJ

Serial #: CWOOO, 1 1111. 22222, 333.33. 444444. 55555

4. £stitn;itk>n of Uncertiiint}

Table 2 summarizes the calculated uncertainty at varioas stages oftesting. First, the uncertainty accrued during the transfer of calibration to the transfer standard (KSR) from the primar\ radiometric standard is based on previous measurements and is expected to bo 0.6 **o. Second,

uncertainties occur while transfcmng the ESR calibration to the heal Ilux sensor using the X'TBB

for broadband testing. The temperature of the \TBB durmg the lest was stable to within 0. 1 K

of tlie set value. Tlie output of ESR and the sensor w ere recorded for about 20 s to 30 s depending on tlie heat flux level. Tlie standard devialion of the mean of tlie readings w as found

to be within about 0.2 of the mean value at heat flux levels greater than 1 W cm". The errors due to alignment are expected to be less than 0.4 "o. since a fixed length gage block was used to

locale tlie ESR and the gage in front of the V "IBB.

Item !0 in Table 2 gives the results of uncertainty from several tests on the reference SchmidtBoelter sensor in the same facility and using similar instrumentation and experimental setup. The uncertainty based on the long-term repeatabilit\' of the calibration of tlie reference sensor has been conservatively added in the calculation of the total relative expanded uncertainty for a coverage factor k-2 [2].

5. General Information

nie results of this calibration appl\' onK' to the sensors referenced in this report. Tliis report

shall not be reproduced, except in full, without the w ritten approx al of this laboratory'.

Prepared by: Approved by:

Charles E. Gibson Gerald T. Fraser Optical Technology' Division For the Director, Physics Laboratory National Instiurte of

(301) 975-2329 Standards and Technology

f 1 1 A. V. Murtiiv, B. K. Tsai, and C. E. Gibson. "Calibration of Higli Heat Flux Sensors al NIST," J. Res. Natl. Inst. Stand Technol. 102. 479-488 (1997).

[2] B. H. Taylor and C. E. Kuyatt, "Guidelines for Evaluating and Expressing tlie lincertainty of tlie NIST Measureroeirt Results," NIST Technical Note 1297 (2" ed.

(301)975-3797

References:

1994). SAMPLE

Calibration Date: August 19, 1999 NIST Test No.: 844 000000-99 Page 3 of

9

25
REPORT OF C:ALIBIUTI0N Manufacturer HF Sensors

3 5070S Special Test ol' Heat FUl\ Sensor Model : HFr-X-OOOOOJ

Riidioraetric Systems Inc. Serial #: 00000, 1111 1 . 22222. 33333. 444444. 55555

Table la Heat Flux Calibration Results for sensors 00000, 11111 and 22222

S/N OOOOO S/N 11111 SfN 22222

Biackbody

lenjperature

, JK1

Incident Flux

IVV/cm^l

Sensor Output

(mV|

Incident Fluv Sensor Output

fnV]

Incident Flux

f\\7cm-|

Sensor Output

!«nV| 298 0.000 o.ooo 0.000 0.000 0.000 0.000

1573 0.83g 2.577 0.8.36 2.483 0.840 2.456

1773 1.290 3.978 1.283 3.817 1.290 3.769

]

1973 1.897 5.835 1.881 5.598 1.884 5.514 2123 2.453 7 556 2,457 7.319 2.454 7.176' 2273 3.142 9.665 3.143 9.362 3.159 9.250 2353 3.568 10 974 3.576 10.668 3.574 10.443 2453 4.151 12.795 4.173 12416 4.177 12 192 2553 4.812 14.862 4.833 14.439 4 831 14.134

j 2593 5.122 15 278 5.115 14.966 2603 5.180 15.9S9

[ Linear regression results for calibration data

1 S/N 000(10 S/.M1I11 S/N 22222 1 Error MS 235E-04 2.10E-04 l.OlE-04 Count 10 10 10 \ Intercept -0.008 -0.012 O.tXJO Slope 3.084 2.985 2.924

R-square 1.000 1.000 1.000 1

Calibration Dats: .August 19, 1999 NIST Test No.: 844. 000000-99 Page 4 of 9

26
REPORT OF C:ALIBR.\TI0N Manufacturer Hf Semors

35070S Special Test ol' Meat Flux Sensor Model: IWT-X-mmJ

R.-idiometric Systems Inc. Serial #: (XJOOO, II 1 11. 22222, 33333. 444444. 55555

Table lb

Heat Flux Calibration Results for sensors 33333, 44444 and 55555

S/N 33333 S/N 44444 S/N 55555

Temperatiirt

J 1**1

Incident Flux Sensor Output

imyi

Incident Flux [W/cm*|Sensor Output

ImM

Incident Flux

I\\7cm-|

Sensor Output :

0.000

]

1 298 0.000 0.000 0.000 0.000 0.000

1 1573 0.834 2.947 0.838 2.992 0.855 2.713 1773 1.283 4.536 1.286 4.612 1.308 4.17-7

] 1973 1.874 6.646 1.894 6.795 1.908 6.100

7.953"""] 2123 2.454 8.702 2,461 8.842 2.489 2273 3.154 11.162 12.648

3.163 11.378 3.188 10.212'" 2353 3.587 3.592 12.947 3.626 11.577 2453 4.166 14.753 4.201 15.121 4.216 13.502 2553 4.841 17.112 4.875 17.582 4.891 15.657 2593 5.116 18.145 5.161 18.643 5.162 16.557 ,

Linear regression results for calibration data

S/N 33333 S/N 44444 S/N 55555 1 Error .VIS 5.75E-04 4.22E-04 2.84K-04 I Count 10 10 10

Intercept -0.002 -0.031 -0.018 Slope 3.540 3.612 3.206 R-square 1.000 1.000 1.000

SAMPLE

Calibrdtion Date: August 19, 1999 NIST Test No.; 844 000000-99 Page 5 of 9

27
REPORT OF C ALIBRATION

35070S Special Test of Heat Flux Sensor

RadiomeU-ic Systems Inc.

Manufacliirer: HF Sensors Model: HFT-X-OOOOOl

Serial f?: 00000. 1 H 11, 22222, 33.13.^ 444444, 55555

SAMPLE

Calibration Date: .August 19. 1999 NIST Test No. : 844 000000-99 Page 6 of 9

28
REPORl OF CALIBRATION

35070S SfTccia] Test of Heat Flux Sensor

Radiomelric Sysleins Inc.

ManiilacUircr: HI' Sensors Model; HFT-X-fX)0(K)J

Serial fk (WOOO. 11111, 22221 33333, 444444. 55555

SAMPLE

Calibration Date: .%igust 19, 1999 NIST Test No. : 844 000000-99 Page 7 of 9

29
REPORT OF CALIBRATION Mamifacttirer: HF Sensors 35070S Special Test of Heal FUix Sensor Model: HIT-X-OOOOOJ

Radiometric Svstems Inc. Serial #: 00000, Hill. 22222, 33333. 444444. 55555

Table 2 Heat Flux Calibration l^ncertainties (Heat Flux Ranse 1 Wicm' to 5 VV/cni^)

Source of Uncertainty Type Uncertainty !%}

1 . Transfer suindard ESR (Previous caiibration) B

2. B!ackl)ody temperature B O.I

3. Biackbodv emissivits' B 0.0

4. Biackbodv aperture uniformity B

' 0.0

5. ESrt and sensor alignment in VTBB - linear

: B 0.4

6. ESR and sensor alignment in VTBB - angular B 0.1

7. Radiometer averaging effect B 0.1

8. ESR reading A ^0.2

9. Sensor reading A 0.2

10. Repeat tests on a s i milai" sensor B 0.7 Relative expanded uncertaintj (U - Auc) l.I Relative expanded uncertainty' (U = k»c) t-2 2.1

SAMPLE

Calibration Date: .\ugust 19, 1999 NIST Test No. : 844/000000-99 Page 8 of 9

30
Appendix C

VTBB operation: Laboratory procedure manual

RTMLP Safety.l Safety Issues

RTMLPl Running General Data Taking Program

RTMLPl1 : VTBB Operation

31
Optical Technology Division (844)

Radiance Temperature Measurements Laboratory Procedure

Safety Issues

Written by: Charles Gibson

Approved by:

Revised by:

Procedure:

Date:

Date:

RTMLPl

Safety Issues

Safety glasses are required in the laboratory at all times.

The following hazards have been identified in this laboratory. Safety measures are in

place to reduce the risk of injury from the hazards below.

BRIGHT SOURCE

Avoid staring at the source Can cause eye damage

Use the correct neutral density filter when viewing is required

BURN

Keep body and clothes away

COLLISION

Keep the boxcar path clear

Do not hang cables from boxcar

ELECTROCUTION

High voltage connections present

Do not touch electrical parts

LASER

Avoid staring into a laser

Can cause eye damage

Block laser or turn off when not in use

Displays, similar to the one below, are used throughout this document to alert the

operator to potential hazards.

LASER

RTMLP Safety. 1 Page 1 of 1

32
Optical Technology Division (844)

Radiance Temperature Measurements Laboratory Procedure

Running General Data Taking Program

Written by: Charles Gibson Procedure: RTMLPl

Approved by: Date:

Revised by: Date:

Running the General Data Taking Program

1 . Turn on the computer

2. Enter the password to w^ork online, or click on the Cancel button to work offline

3. Load the Visual Basic program: c:\programs\datatakn\pyro.mak (do one of the

following)

a. Click on the Pyro.mak shortcut icon

b. Double click on the folder c:\programs\datatakn\pyro.mak using Windows

Explorer

4. Run the program (do one of the following)

a. Press F5

b. Click on the _ tool bar icon

c. Click on the menu item "Run" then on "Start"

5. The Hardware.frm is used to set up the equipment with settings used by other

programs

6. The Software.frm is used to input data used by other programs

7. All other programs can be run from these forms

RTMLPl Page 1 of 1

33
Optical Technology Division (844)

Radiance Temperature Measurements Laboratory Procedure

Variable-Temperature Blackbody Operation

Written by: Charles Gibson

Approved by:

Revised by:

Procedure:

Date:

Date:

RTMLPll

VTBB Operation

m

BRIGHT SOURCE

BURN

ELECTROCUTION

1. Turn On Procedure

a. Open tap water valve 1/8 turn

b. Check that the blue box flow rate is about 2 GPM

c. Open chilled water valves

i. open supply valve 1/4 turn

ii. fully open return valve

d. Press the reset button on the blue water switch box to select chilled water

e. Check that the blue box flow rate is about 5 GPM

f. Fully open the argon cylinder valve

g. Turn on the argon alarm and check that it trips at 10 CFH

h. Purge the BB using a argon flow rate of 70 CFH

i. Cover both BB openings for 5 s with your hands

ii. Uncover one end and wait 5 s

iii. Cover both BB openings for 5 s with your hands

iv. Uncover the other end and wait 5 s

i. Repeat step h 5 times

j. Reduce the argon flow rate to 10 CFH

k. Check that the BB housing is cool and that the argon is flowing

1. Insert correct detector filter for the initial set point

i. FilterO, 700 to 1300 °C, Low with insulation (LIN)

ii. Fiher 1 , 1 300 to 1 800 °C, Medium (MED)

iii. Filter 2, 1 800 to 2500 °C, High (HI)

iv. Filter 3, 2500 to 3 100 °C, Extra High(XH)

m. Switch control mode to [MANUAL]

n. Turn the potentiometer to 0

o. Press the [START], [WATER ON], and [RUN] buttons

i. Note: The BB does not control the chilled water flow the automatic

BB shut off switch has been disabled

p. Turn the potentiometer slowly until the voltmeter reads between 150 VAC

and 200 VAC (sets BB below 1 300 °C)

RTMLPll Page 1 of 3

34
Optical Technology Division (844)

Radiance Temperature Measurements Laboratory Procedure

Variable-Temperature Blackbody Operation

Written by: Charles Gibson

Approved by:

Revised by:

Procedure: RTMLPll

Date:

Date:

2. Operating Procedure

a. Run the BB control program

11. Program is RRPROG PRG in RetterRasic

11 Fnter RR f\i the DOS nromnt

Ill ill

.

Pntpr mpfi<siirpmpnt Hirpption

( 1 ) ' 0' to run high to low

(2) '1' to run low to high

iv. Enter set point unit

(1) 'C'for°C

(2) 'F' for ° F

V. Enter temperature range

(1) LOW

(2) LIN

(3) MED

(4) HI

(5) XH

vi. Insert the correct filter and press [Enter]

b. Press [Shift S] to enter the initial set point

c. Adjust the potentiometer until the temperature is 20 °C above the set point

d. Switch the control mode to [PC] to maintain the set point

WARNING!

DO NOT INCREASE THE SET POINT BY STEPS LARGER THAN

20 °C TO REDUCE DAMAGE TO THE BB

e. Select a new set point (the set point is in °C or °F depending on set point

unit selected)

i. Press [Shift S] to enter the set point

ii. Use the numeric keypad to increment the set point

(1) Press the increment key

(a) 100 °c (7' key)

(b) 10 ('4' key)

(c) 1 (Tkey)

(d) 0.1 ('0' key)

(2) Press the Arrow key to set the new set point

(a) T, to increase the set point ('8' key)

(b) i, to decrease the set point ('2' key)

RTMLPll Page 2 of 3

35
Optical Technology Division (844)

Radiance Temperature Measurements Laboratory Procedure

Safety Issues

Written by: Charles Gibson Procedure: RTMLPll

Approved by: Date:

Revised by: Date:

f. If the new set point is not in the current range then the program will pause

(suspending BB control)

i. Depending on the measurement direction the default set points are

(1) High to low default set points

(2)

(a) XH 2500 °C

(b) HI 2300 °C

(c) MED 1800 °C

(d) LOW 1300 °C

Low to high default set points

(a) LOW 800 °C

(b) MED 1300 °C

(c) HI 1800 °C

(d) XH 2500 °C

ii. If the new set point is not the default value, then switch the control

mode to [MANUAL]

iii. The program will loop to step 2.a.v. (see ^)

3. EMERGENCY TURN OFF Procedure

a. Press the [EMERGENCY STOP] button on the power supply (the chilled

water and argon will continue flowing)

b. Continue with steps 4.b. to 4.j.

4. Turn Off Procedure

a. Switch the control mode to [MANUAL]

b. Turn to potentiometer to 0

c. Press the [EMERGENCY STOP] button on the power supply (the chilled

water and argon will continue flowing)

d. Switch off the main breaker on the wall

e. Wait until the furnace has stopped glowing

f. Close the chilled water supply valve

g. Close the chilled water retum valve

h. Close the cold water supply valve

i. Close the argon cylinder valve

j. Close the argon flow meter valve

RTMLPll Page 3 of 3

36
Appendix D: How to Request Heat-Flux Sensor Calibrations

1 . Prepare a purchase order with the following:

a. Company name and address

b. Contact person's name and phone number

c. Billing address

d. Service ID number requested (include range and points)

e. Test fee

f. Address to ship test item

g. Return shipping instructions (prepay and add, COD, charge to account with shipper)

i. the test fee does not include shipping costs

ii. customers are responsible for all shipping costs

iii. If no instructions are given, NIST will return the test item by common carrier,

collect, and uninsured.

2. Send the purchase order to: Calibration Services

National Institute of Standards and Technology

100 Bureau Drive, Stop 2330

Gaithersburg, MD 20899-2330

Tel.: (301) 975-2002

FAX: (301) 869-3548

E-mail:

calibrations@nist.gov

3. Send the test item(s) to: Charles Gibson

National Institute of Standards and Technology

1 00 Bureau Drive, Stop 844

1

Gaithersburg, MD 20899-8441

Tel.: (301)975-2329

FAX: (301) 869-5700

E-mail: cgibson(a)nist.gov

WWW: http://physics.nist.gov/Divisions/Div844/staff7Gp3/gibson.html

Heat-flux sensor calibrations are performed in February, May, August, and November.

Requests for calibration services are scheduled after the receipt of a purchase order.

NIST policy requires prepayment of all calibration services performed for non-U. S. organizations. Please contact the Calibration Program office to arrange payment.

37