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Radiance Temperature Laboratory

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Program Objective: This laboratory has as its principal activity the establishment, maintenance, and dissemination of the US National Scale of Radiance Temperature. This laboratory is responsible for temperature measurements above the freezing point of silver (1234.93 K or 961.78 °C).

The 1990 NIST Radiance Temperature Scale is the NIST realization of the International Temperature Scale 1990 from blackbody physics. The radiance temperature of a radiator is equivalent to the temperature of a blackbody with the same radiant intensity of the radiator's surface at a fixed wavelength.

Click on the items below to read more about:

Radiance Temperature Laboratory Measurement System
Schematic of the Radiance Temperature Laboratory Measurement System
LEGEND
 
AMP Amplifier PS Power Supply
DVM Digital Voltmeter RS Room Humidity Sensor
EM Environmental Monitor TC Thermoelectric Cooler
GPBB Gold-point Blackbody TL Test Lamp
GPL Gold-point Lamp TS Temperature Sensor
PC Personal Computer VTBB Variable Temperature Blackbody
PMT Photomultiplier Tube WSL Working Standard Lamp

Radiance Temperature Scale Realization

  • A gold freezing point blackbody (reference standard) and the Planck radiation law are used to realize and disseminate the 1990 NIST Radiance Temperature Scale.


    The Planck equation:
equation 1     (1)

equation 2     (2)
   
where lambda  = wavelength in air [cm]
epsilonlambda  = Spectral emissivity = 1 for ideal blackbody
c1L  = first radiation constant in radiance form = c1 / pi = 1.191 043 x 10-12 [W · cm2]
c2  = second radiation constant = 1.4388 [cm · K]
nlambda  = refractive index of air at 15 °C and 76 cm Hg using the Cauchy formula (lambda in Å)
similarly equal 1 + {2726.43 + [12.288 / (lambda2 x 10-8)] + [0.3555 / (lambda4 x 10-16)]} x 10-7
 = 1.000 28 for lambda = 6553 Å


  • The radiance temperature of the working standard is determined by comparison to the gold point blackbody. A high stability vacuum lamp operated at approximately 1255 °C is the working standard.

  • The NIST Photoelectric Pyrometer (PEP) is the transfer device used to compare the spectral radiances of the sources.

  • The PEP is a filtered radiometer which uses two interference filters to select the bandpass. The bandwidth is 5 nm with a mean effective wavelength of 655.3 nm. A photomultiplier tube with a S-20 spectral response is used in the DC mode. The measurement spot size is a 0.6 mm by 0.8 mm rectangle.

NIST Photoelectric Pyrometer
NIST Photoelectric Pyrometer
NIST Photoelectric Pyrometer

LEGEND
 
AS Aperture Stop
CL Collimating Lens
CPD Cooled Photomultiplier Detector
DL Diverging Lens
FS 0.6 mm x 0.8 mm Rectangular Field Stop
GPBB Gold-point Blackbody
GPL Gold-point Lamp
IF Interference Filters
OL Objective Lens
TL Test Lamp
VTBB Variable Temperature Blackbody
WSL Working Standard Lamp


  • The radiance temperature of the test lamp is determined by comparison to the working standard.

  • The variable-temperature blackbody (VTBB) is the transfer standard used to calibrate test pyrometers. The radiance temperature of the transfer standard is determined by comparison to the working standard.

  • The blackbody operates between 800 °C and 2700 °C with an estimated emissivity of 0.99. The blackbody cavity is a single piece of graphite, specially tapered for temperature uniformity. This graphite tube is cylindrically hollow on both ends to form two 2.54 cm diameter cavities with a common partition in the center. One cavity is used for temperature control and the other as a blackbody source.

Radiance Temperature Calibration Services

Calibration reports are issued giving the radiance temperature of the blackbody at 655.3 nm versus scale reading, output current, or output voltage
Test No. Measurement Description
35010C Radiance Temperature Standard, Disappearing Filament Optical Pyrometer (1 pyrometer range, 4 to 12 points, 800 °C to 2400 °C)
35020C Radiance Temperature Standard, Disappearing Filament Optical Pyrometer (per additional range up to 4200C with Test no. 35010C only)
35040C Radiance Temperature Standard, Disappearing Filament Optical Pyrometer (3 or fewer points, 800 °C to 4200 °C)
Calibration reports are issued giving the radiance temperature at 655.3 nm versus direct current
Test No. Measurement Description
35050C Radiance Temperature Standard, Ribbon Filament Lamp (6 to 16 points, 800 °C to 2300 °C)
35060C Radiance Temperature Standard, Ribbon Filament Lamp (5 or fewer points, 800 °C to 2300 °C)
Test reports are issued giving the radiance temperature of the blackbody at 655.3, 900, or 1000 nm versus the indicator reading, output current, or output voltage
Test No. Measurement Description
35070S Special Tests of Radiation Thermometers

Calibration Uncertainties

The expanded uncertainty (coverage factor k = 2) is a two standard deviation estimate.
Standard Temperature Range Expanded Uncertainty
Ribbon filament lamp   800 °C to 1600 °C
1600 °C to 1900 °C
1900 °C to 2300 °C		   0.7 °C
  1.0 °C
 1.5 °C
Leeds & Northrup Model 8000 series

Disappearing filament optical pyrometer		   800 °C to 1600 °C
1600 °C to 2100 °C
1900 °C to 2300 °C
2400 °C to 2700 °C
2700 °C to 3200 °C
3200 °C to 4200 °C		   4 °C
  5 °C
  7 °C
  8 °C
 17 °C
25 °C
Pyrometer Instrument Model 95

Disappearing filament optical pyrometer		   800 °C to 1400 °C
1400 °C to 1800 °C
1800 °C to 2400 °C
2400 °C to 2700 °C
2700 °C to 3200 °C		   3 °C
  4 °C
  5 °C
  8 °C
12 °C
Infrared radiation thermometer   800 °C to 2000 °C
2000 °C to 2700 °C		   2 °C
 3 °C


This laboratory's quality system is based on the ANSI/NCSL Z540-1-1994 standard and the ISO/IEC Guide 25.

How to Request Radiance Temperature Calibration Services

  1. Prepare a purchase order with the following:
    • Company name and address
    • Contact person's name and phone number.
    • Billing address
    • Service ID number requested (include range and points)
    • Test fee
    • Address to ship test item
    • Return shipping instructions (prepay and add, COD, charge to account with shipper)
      • the test fee does not include shipping costs
      • customers are responsible for all shipping costs
      • If no instructions are given, NIST will return the test item by common carrier, collect, and uninsured.

  2. Send the purchase order to:
    National Institute of Standards and Technology
    Calibration Program
    Building 820, Room 232
    Gaithersburg, MD 20899-0001
     
    Tel.: (301) 975-2002
    FAX: (301) 869-3548
    E-mail: calibrations@enh.nist.gov.

  3. Send the test item(s) to:
    Charles Gibson
    NIST
    Building 221 / Room B208
    Gaithersburg, MD 20899-0001
     
    Tel.: (301) 975-2329
    FAX: (301) 869-5700
    E-mail: cgibson@nist.gov.


Radiance temperature 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 Denise Lockard of the Calibration Program office to arrange payment. The Fax number is 301-869-3548. The e-mail address is calibrations@nist.gov.

Groups supported by this calibration service

  • Aerospace industry
  • Industrial users including aluminum, glass, and steel manufacturers
  • NASA
  • National standards laboratories
  • Pyrometer and blackbody manufacturers
  • Research universities
  • US military service calibration laboratories
For technical information or questions, contact:
Charles E. Gibson
Phone: (301) 975-2329
Fax: (301) 869-5700
Email: charles.gibson@nist.gov

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Online: September 1997   -   Last updated: May 2003