Thermopile pyrometer modules are the state of the art for contactless temperature measurements in automotive applications. In such an application, the thermopile has to operate precisely in a challenging thermal environment. While the compensation of the steady state ambient temperature is a well known technique when using thermopiles for temperature measurments, transient thermal effects are still an issue. The change of the ambient temperature as well as temperature flow through the sensor can lead to substantial errors due to unwanted thermal gradients within the device. In the thermopile chip they lead to an error signal since the measurement principle is based on quantifying thermal gradients of the chip that result from the detected IR-radiation. Thermal gradients in the cap and between the cap and the thermopile chip will lead to an exchange of heat radiation between the thermopile chip and the cap, which also leads to measurement errors. Different methods were developed that separately or in combination allow for a significant improvement of the accuracy and signal stability. The methods are based on the reduction of thermal gradients within the thermopile chip and the entire sensor device (isothermal, high thermal mass cap), reduction of radiation exchange between the sensor chip and the housing (low emissive inner cap surface) and prediction and software compensation of the error signal.
We present the main applications for contact-less (radiation-) temperature measurement with thermopile sensors and show how the large number of different requirements associated with them can be matched using a low-cost sensor module construction set in a TO39 housing. The main components are: A choice from different MEMS-thermopile sensors or sensor arrays, one of two programmable ASIC’s, IR optical components to be integrated, such as filters, IR lenses, a Winston cone reflector and different caps. Of the latter, a significant innovation is the isothermal cap, which integrates the mechanical functionality of a cap with optical functions such as the reduction of ghost images and most importantly the thermal functionality of a massive heat sink. This way a complete pyrometer can be build into a TO39 housing.
Uniformity of physical properties of paper continues to be one of the most serious quality issues in today's paper mills. The large-scale `average' profile can often be controlled effectively with today's technologies. However, to detect and control sizes from several microns to a few centimeters remains the industry's biggest challenge. Over the last several years, INO has developed and perfected an entirely new instrument to measure surface fiber orientation. This non-destructive, non-contact technique can more appropriately be described as a surface strain tester. It is slowly finding its way in various laboratories around the world, notably Sweden, United States and France. The instrument uses a custom designed phase-modulated, laser- based ellipsometer in the far infrared spectral region. It basically measures the local surface birefringence and direction of the optic axis. Our approach is highly unusual since it works for samples of widely varying surface roughness and does not require careful alignment of the sample with respect to the laser beam. This paper describes how the instrument works, what it measures and illustrates various applications from small scale mapping to cross- machine profiles.
Laser action was obtained from a small (8 cm3) far infrared laser at several wavelengths between 100 μm and 600 μm. Studies as a function of pump power, gas pressure and temperature were performed, and will be discussed.
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