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Kendall Absolute Radiometers

Product Details

Kendall radiometers are self-calibrating cavity radiometers which provide an accurate absolute standard for total irradiance. The radiometer receiver is a blackbody cavity which has an electrical heater installed so that substituted electrical heating is equivalent to the incoming irradiance at the radiometer aperture. By accurate measurement of the electrical power to the calibration heater, together with the thermopile response, the radiometer is calibrated without reference to other standards. These radiometers were originally developed by J.M. Kendall, Sr. and C.M. Berdahl at NASA-JPL as reported in Applied Optics 9(5): 1082-1091 in the 1970’s. They have been manufactured by Raptor Scientific since 1996, to the original Kendall/Berdahl and TMI drawings and specifications. Raptor Scientific is the only  

Applications 

  • Kendall Radiometers produced by Raptor Scientific are primarily used for the testing of satellites 
  • The products are also used in the green power industry with solar panels and solar concentrating power plants 
  • They have the ability to measure up to 20 solar constants (20x the power of the Sun)

There are six Kendall absolute radiometers currently offered, with three different Control Units 

The Kendall MK I Control Unit combined with a Kendall MK IV, MK VI, or MK XI Radiometer forms a complete measuring system ideally suited for use in a wide variety of applications requiring the accurate measurement of irradianceThe Control Unit displays continuously the digital value of the irradiance in any desired absolute units, usually kW/m2It is complete within itself (except for radiometer temperature control equipment for the MK V radiometers) and contains all necessary maintenance self-check and calibration equipment. State of the art components used include a low noise, ultra-low drift amplifier system, and a high accuracy, high resolution digital voltmeterBoth analog and RS-232 digital outputs of measured irradiance are provided for incorporation into a data acquisition systemThe control unit and Kendall radiometer form a complete measuring system of the highest accuracy which is particularly convenient and represents continued excellence in the art of radiometry. 

Features 

  • Convenient to Use 
  • Digital Reading in Absolute Energy Units 
  • Self-Checking 
  • Calibration Power Supply 
  • Output for Data Acquisition Systems 

 

Specifications 

Accuracy: Absolute measurement uncertainty is less than ± 0.5% of the Kendall radiometer full scale range. 

Zero Drift: < ±0.1%/ month of Kendall radiometer full scale range. 

Time Constant: <2 seconds (l/e) 

Display: ± 99,999 counts normal range. 

Analog Outputs: ± 4 volts 

Digital Outputs: RS-232 

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

Weight: 10 kg (approx.) 

 

The Kendall MK IV radiometer is a self-calibrating, cavity type radiometer for measurement of total irradiance up to 30 solar constants or 4.2 watts/cm2. The most essential part of this radiometer is the internally blackened cavity which constitutes a small blackbody. Thermally connecting the cavity to the main body of the radiometer is a thermal resistor which conducts heat produced in the cavity to the main body. The temperature drop across the thermal resistor (measured by a thermopile) serves as a measure of heat flux through the thermal resistor. The heat flux is produced either by incoming irradiance or by the electrical calibration heater built into the cavity. By accurately measuring the electrical power to the calibration heater together with the thermopile response, the radiometer is calibrated without reference to other standards, and thus may be termed an absolute radiometer. The radiometer incorporates provisions for temperature controlling the main body by water cooling. The MK IV has gained acceptance as a standard for solar simulation intensity measurements and as a standard for heat flux calibrations. The MK IV Radiometer requires a MK I Control Unit to make a complete operating system. 

Features 

Precise Measurement of Total Radiation in the Range of 0.02 to 4.2 watts/cm2 

High Accuracy 

Self-Calibrating 

Spectrally Insensitive 

Wide Irradiance Range 

Rugged Construction 

Specifications 

Range: 0.02 to 4.2 watts/cm2 

Accuracy: ± 0.5% of reading ± 0.2 mW/cm2 

Time Constant: 6 seconds (1/e) 

Sensitivity: Greater than 15 mv per watt/cm2 

View Angle: 85° 

Calibration Heater: 200 ohm (approx.), 150 mA maximum 

Outer Surface Coating: 0.005 mm pure gold plate 

Mounting: 5 mm metric machine screw (also 10-32) 

Cabling: 4 meters long, Bendix PT06A-14-19P connector  

Size: 51 mm dia x 76 mm high 

Weight: 1 kg (approx.) 

The Kendall MK V radiometer is a self-calibrating, cavity type radiometer for measurement of total irradiance up to over 2 solar constants or to 2.8 kilowatts/m2. The MK V radiometer is designed for use in solar thermal vacuum chambers with LN2 cooled walls. The most essential part of this radiometer is the internally blackened cavity receiver that constitutes a small blackbody. Thermally connecting the cavity to the main body of the radiometer is a thermal resistor that conducts heat produced in the cavity to the main body. The temperature drop across the thermal resistor (measured by a thermopile) serves as a measure of heat flux through the thermal resistor. The heat flux is produced either by incoming irradiance or by the electrical calibration heater built into the cavity. By accurately measuring the electrical power to the calibration heater together with the thermopile response, the radiometer is calibrated without reference to other standards, and thus may be termed an absolute radiometer. The radiometer incorporates provisions for temperature controlling the main body by electrical heating. The MK V has gained acceptance as a standard for solar simulation intensity measurements in solar thermal vacuum testing. 

The MK V Radiometer requires a MK Ia Control Unit, which includes a body temperature controller, to make a complete operating system 

Features 

Precise Measurement of Total Radiation in the Range of 0.02 to 2.8 kilowatts/M2 

High Accuracy 

Self-Calibrating 

Spectrally Insensitive 

Wide Irradiance Range 

Rugged Construction 

Electric Heater Body 

Temperature Control For Use In Ln2 Cooled Chambers 

 Specifications 

Range: 0.02 to 2.8 kilowatts/m2 

Accuracy: ± 0.5% of reading ± 0.1 mW/cm2 

Time Constant: 6 seconds (1/e) 

Sensitivity: Greater than 10 mV per W/cm2 

View Angle: 86° 

Calibration Heater: 200 ohm (approx.), 40 mA maximum 

Outer Surface Coating: 0.005 mm pure gold plate 

Mounting: 5 mm metric machine screw (also 10-32) 

Cabling: 4 meters long, Bendix PT06E-14-19P connector 

Size: 74 mm dia x 91 mm high with sunshade 

Weight: 1 kg (approx.) 

 

The Kendall MK VI radiometer is a self-calibrating, cavity type normal-incidence pyrheliometer of unsurpassed accuracy. The most essential part of this radiometer is the internally blackened cavity which constitutes a small blackbody. Thermally connecting the cavity to the main body of the radiometer is a thermal resistor which conducts heat produced in the cavity to the main body. The temperature drop across the thermal resistor (measured by a thermopile) serves as a measure of heat flux through the thermal resistor. The heat flux is produced either by incoming irradiance or by the electrical calibration heater built into the cavity. By accurately measuring the electrical power to the calibration heater together with the thermopile response, the radiometer is calibrated without reference to other standards, and thus may be termed an absolute radiometer. The radiometer incorporates a thermally insulating view limiter case. The MK VI has gained acceptance as a standard for insolation intensity measurements. This radiometer has participated in the International Pyrheliometer Comparisons at Davos, Switzerland in 1975, 1980, 1985, and 1990. 

The MK VI Radiometer requires a MK I Control Unit to make a complete operating system. 

Features 

Precise Measurement of Normal Incident Solar Irradiance 

High Accuracy 

Self-Calibrating 

Spectrally Insensitive 

Rugged Construction 

Specifications 

Range: 0.02 to 0.2 watts/cm2 

Accuracy: ± 0.5% of reading ± 0.2 mW/cm2 

Time Constant: 6 seconds (1/e) 

Sensitivity: Greater than 15 mv per watt/cm2 

View Angle: 5° solid angle 

Calibration Heater: 200 ohm (approx.), 150 mA maximum 

Outer Surface Coating: Anodized aluminum 

Mounting: 1/4-20 machine screw  

Cabling: 20 feet long, Bendix PT06A-14-19P connector 

Size: 10 cm dia x 33 cm high (approx.) 

Weight: 3 kg (approx.) 

 

The Kendall MK VIII radiometer is a self-calibrating, cavity type radiometer for measurement of total irradiance up 2000 watts/cm2 or 20,000 solar constants (defined as 1 kW/m2 at the earth’s surface). The most essential part of this radiometer is the internally blackened cavity which constitutes a small blackbody. Thermally connecting the cavity to the main body of the radiometer is a thermal resistor that conducts heat produced in the cavity to the main body. The temperature drop across the thermal resistor (measured by a thermopile) serves as a measure of heat flux through the thermal resistor. The heat flux is produced either by incoming irradiance or by the electrical calibration heater built into the cavity. By accurately measuring the electrical power to the calibration heater together with the thermopile response, the radiometer is calibrated without reference to other standards. The radiometer incorporates provisions for temperature controlling the main body by water cooling. The MK VIII has gained acceptance as a standard for high intensity solar concentrator radiation measurements. The MK VIII System includes the MK X Mini-Control Unit and is complete ready to operate. 

Features 

Precise Measurement of Total Radiation in the Range of 200 kW/m2 to 20,000 kW/m2 

High Accuracy 

Self-Calibrating 

Spectrally Insensitive 

Wide Irradiance Range 

Rugged Construction 

Specifications 

Range: Between 200 kW/m2 and 20,000 kW/m2, depending on aperture size 

Accuracy: ± 1% of reading 

Time Constant: 1.3 seconds (1/e) 

Sensitivity: Greater than 8 microvolts per kW/m2 

View Angle: Perfect cosine response up to 60° off axis 

Calibration Heater: 55 ohm (approx.), 0.7 ampere maximum 

Outer Surface Coating: Silver plate 

Mounting: Water cooled sting 3/4″ dia. x 10″ long 

Cabling: 1 meter long, Bendix PT06A-12-10P connector 

Size: 5.7 cm dia x 11.9 cm long 

Weight: 2 kg (approx.) 

 

The Kendall MK IX radiometer is a self-calibrating, cavity-type radiometer for measurement of total irradiance up to 1000 watts/cm2. The most essential part of this radiometer is the internally blackened cavity which constitutes a small blackbody. Thermally connecting the cavity to the main body of the radiometer is a thermal resistor that conducts heat produced in the cavity to the main body. The temperature drop across the thermal resistor (measured by a thermopile) serves as a measure of heat flux through the thermal resistor. The heat flux is produced either by incoming irradiance or by the electrical calibration heater built into the cavity. By accurately measuring the electrical power to the calibration heater together with the thermopile response, the radiometer is calibrated without reference to other standards. The radiometer incorporates provisions for temperature controlling the main body by water cooling. The MK IX has gained acceptance as a standard for high-intensity radiation measurements. The MK IX System includes the MK X Mini-Control Unit and is complete ready to operate. 

Features 

Precise Measurement of Total Radiation in the Range of 15 watts/cm2 TO 1000 watts/cm2 

High Accuracy 

Self-Calibrating 

Spectrally Insensitive 

Wide Irradiance Range 

Rugged Construction 

Specifications 

Range: Between 15 watts/cm2 and 1000 watts/cm2, depending on aperture size 

Accuracy: ± 1% of reading 

Time Constant: 1.8 seconds (1/e) 

Sensitivity: Greater than 0.30 mV per watt/cm2 

View Angle: Perfect cosine response up to 60° off axis 

Calibration Heater: 55 ohm (approx.), 0.7 ampere maximum 

Outer Surface Coating: Silver plate 

Mounting: Water cooled sting 3/4″ dia. x 10″ long 

Cabling: 1 meter long, Bendix PT06A-12-10P connector 

Size: 5.1 cm dia x 5.1 cm long 

Weight: 1 kg (approx.) 

 

 

 

The Kendall MK X is a mini-control unit provided with the MK VIII and MK IX radiometers and is not sold separately. A precision external digital multimeter, a precision external power supply, and an external temperature reference must be supplied by the user  

The Kendall MK XI radiometer is a self-calibrating, cavity type radiometer for measurement of total irradiance up to 20 watts/cm2. The most essential part of this radiometer is the internally blackened cavity that constitutes a small blackbody. Thermally connecting the cavity to the main body of the radiometer is a thermal resistor that conducts heat produced in the cavity to the main body. The temperature drop across the thermal resistor (measured by a thermopile) serves as a measure of heat flux through the thermal resistor. The heat flux is produced either by incoming irradiance or by the electrical calibration heater built into the cavity. By accurately measuring the electrical power to the calibration heater together with the thermopile response, the radiometer is calibrated without reference to other standards and thus may be termed an absolute radiometer. The radiometer is temperature controlled by water cooling, with no wetted joints inside the radiometer body. The MK XI has design features of the MK IV and MK IX absolute radiometers, which have gained acceptance as standards for high intensity radiation measurements. 

The MK XI Radiometer must be used with a MK I Control Unit to make a complete operating system. 

Features 

Precise Measurement of Total Radiation in the Range of 0.1 watts/cm2 to 20 watts/cm2 

High Accuracy 

Self-Calibrating 

Spectrally Insensitive 

Wide Irradiance Range 

Rugged Construction 

Specifications 

Range: Between 0.1 watts/cm2 and 20 watts/cm2 

Accuracy: ± 1% of reading 

Time Constant: Approximately 7.5 seconds (63.2%) 

Sensitivity: Approximately 4.5 mV per watt/cm2 

View Angle: Perfect cosine response to over 60° off axis 

Calibration Heater: 200 ohm (approx.), 150 mA maximum 

Outer Surface Coating: 0.005mm pure gold plate 

Mounting: Water cooled sting 3/4″ dia. x 10″ long 

Cabling: 4 meters long, Bendix PT06A-14-19P connector 

Size: 4.78 cm dia x 9.9 cm long plus 25.4 cm mounting 

Weight: 1.5 kg (approx.) 

The 50500 Kendall Radiometer Filter unit is a 12-conductor low-pass guarded passive filter intended for use with the MK V Kendall Absolute Cavity Radiometer/MK Ia Radiometer Control Unit system for measurement of irradiance in space simulation chambers or in other situations with potential noise problems. The Kendall Absolute Cavity Radiometer system is designed for measuring irradiance without reference to other radiometric standards. The 50500 Filter is an optional component of that system.  

The Filter unit was designed and developed by James Kendall, Martin Berdahl, and John Stallcamp of NASA-JPL for use with the Kendall Radiometer system in the NASA-JPL space simulation chamber and was configured for that facility. It is expected to perform in a similar way in any similar facility. 

 

Specifications 

Range: May be used with any of our Kendall Radiometers 

Accuracy: Pass-through design filter does not affect the accuracy of the radiometer system when the electrical substitution calibration is performed in the user environment with the Filter Unit in place. 

Cable: ½ m long cable with Amphenol PT06A-14-19P type connector on each end. 

Size: 10.2 cm H x 43.2 cm W x 33 cm D (4” H x 17” W x 13” D) 

Weight: approx. 27 kg (approx. 12.3 lb.) 

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