Surface Optics SOC ET-100 Thermal Emissometer

Surface Optics SOC ET-100 Thermal Emissometer Overview

The Surface Optics SOC ET-100 thermal emissometer measures directional hemispheric reflectance (DHR) in six bands in the thermal infrared spectral region (1.5 to 21μm) at two incidence angles, 20° and 60° in accordance with ASTM E408 and E1980. Based on those values, directional and total hemispherical emissivity are calculated. In addition, an optional 410 Solar reflectometer head can be attached to the ET-100’s command module which provides for measurements of near-normal reflectance (total hemispheric, diffuse and specular) averaged within 7 wavebands from 330 to 2500nm in accordance with ASTM E903 and C1549, the standard test methods for solar reflectance measurements. Combining the results from the 410 Solar and the ET-100 measurement heads provides for measurements of reflectance, solar absorptance and thermal emissivity. From this data set, the solar reflectance index (SRI) can be computed in accordance with ASTM E1980 (Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low-Sloped Opaque Surface).

Please note that the ET-100 can serve as a replacement for the discontinued DB-100 radiometer made by Gier Dunkle. 

The ET-100 is Part of the Surface Optics 410 Family

The ET-100 forms part of the 410 range of portable reflectometers and emissometers from Surface Optics Corporation (SOC) that are designed for reflectance, solar absorbance and thermal emissivity measurements in the visible to far infrared range. These modular devices feature interchangeable measurement heads and a common command module and generate data of comparable quality to much larger laboratory instruments. Please note that you can order the ET-100 with the additional 410 Solar measurement head as a package – this is known as the 410 VIS IR.

ET-100 for Total Hemispherical Emissivity Measurements

The ET-100 provides for measurements of reflectance and thermal emissivity in the 1.5-21μm waveband. Measurements of total hemispheric reflectance are made with the ET-100 head at 20° and 60° incidence and averaged within 6 wavebands between 1.5 to 21μm. Measurements are made in the following bands: 1.5-2μm; 2-3μm; 3-4μm; 4-5μm; 5-10μm; and 10-21μm. The ET-100 employs a thermal filament source maintained at 1000°C within an integrating sphere. The integration of these values with the Planck function gives the directional thermal emissivity, from which the hemispheric thermal emissivity is computed. The ET-100 is compliant with ASTM E408 (Total Normal Emittance of Surfaces Using Inspection-Meter Techniques).

Emissivity is that property of a material that determines its effectiveness at emitting thermal radiation, defined as the ratio of the quantity of thermal radiation emitted from a surface compared to the perfect black body radiator maintained at the same temperature, given by the Stefan-Boltzmann law. The measurement of emissivity is important for the calibration of pyranometers and thermal cameras which make non-contact temperature measurements.

Optional 410 Solar Head for Reflectance & Solar Absorptance Measurements

The 410 Solar measurement head can be used with the ET-100’s base unit and provides for measurements of reflectance (total hemispheric, diffuse and specular) averaged within 7 wavebands from 330 to 2500nm. The 410 Solar i model differs only in the ability to measure just the total hemispherical reflectance of a sample (diffuse versus specular reflectance are NOT reported). Measurements are made in the following bands: 335-380nm; 400-540nm; 480-600nm; 590-720nm; 700-1100nm; 1000-1700nm; and 1700-2500nm. The 410-Solar employs a tungsten lamp with integrating sphere for measurements in a 20°/H geometry (directional illumination at 20° to surface normal with hemispheric collection). Solar absorptance is calculated for a number of solar irradiance (air mass) functions, including AM0 (extra-terrestrial) and AM1.5 (terrestrial).

The 410 Solar is compliant with ASTM E903 (Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres) and C1549 (Determination of Solar Reflectance Near Ambient Temperature Using a Portable Solar Reflectometer). 

Combined 410 Solar & ET-100 Measurement Capabilities

Combining the results from the 410 Solar and the ET-100 measurement heads provides for measurements of reflectance, solar absorptance and thermal emissivity. From this data set, the solar reflectance index (SRI) can be manually computed by the operator in accordance with ASTM E1980 (Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low-Sloped Opaque Surface).

Ergonomic Design

The lightweight pistol-grip design of the ET-100 is modelled on a battery operated power tool. It is highly portable and allows single-handed use. Simply hold the sample port against the surface to be tested and press the trigger to take the measurement. View results immediately on the touch-screen display. Measurements can be taken on curved surfaces without special jigs or fixtures. The ET-100 measures the reflectance and emissivity of flat, convex and concave surfaces (max. 150mm & 300mm radius, respectively) with a measurement spot of 12.7mm diameter.

An optional bench-top remote control unit (RCU) is available for the ET-100 and operates by remote external control from a customer-supplied Windows PC. The bench-top configuration is ideal for routine QC applications and for installations where the ET-100 measurement head is mounted on a robot arm.