Development of Novel Thermal Diffusivity Analysis by Spot Periodic Heating and Infrared Radiation Thermometer Method

A spot periodic heating method is a highly accurate, non-contact method for the evaluation of anisotropy and relative thermophysical property distribution. However, accurately evaluating thermal diffusivity is difficult due to the influence of temperature wave reflection from the whole surface of the sample. This study proposes a method to derive thermal diffusivity using a parameter table based on heat transfer equations using the concept of optimum distance between heating-point and measurement point. This method considers finite sample size, sensitivity distribution of infrared ray detector, intensity distribution of heating laser and sample thickness. In these results, the obtained thermal diffusivity of pure copper corresponded well with previous literature values. In conclusion, this method is considered highly effective in evaluating the thermal diffusivity in the horizontal direction.

Zero Drift Infrared Radiation Thermometer Using Chopper Stabilised Pre-Amplifier

A zero-drift, mid–wave infrared (MWIR) thermometer constructed using a chopper stabilised operational amplifier (op-amp) was compared against an identical thermometer that utilised a precision op-amp. The chopper stabilised op-amp resulted in a zero-drift infrared radiation thermometer (IRT) with approximately 75% lower offset voltage, 50% lower voltage noise and less susceptibility to perturbation by external sources. This was in comparison to the precision op-amp IRT when blanked by a cover at ambient temperature. Significantly, the zero-drift IRT demonstrated improved linearity for the measurement of target temperatures between 20 °C and 70 °C compared to the precision IRT. This eases the IRT calibration procedure, leading to improvement in the tolerance of the temperature measurement of such low target temperatures. The zero-drift IRT was demonstrated to measure a target temperature of 40 °C with a reduction in the root mean square (RMS) noise from 5 K to 1 K compared to the precision IRT.

Influence of Size of Source Effect on Accuracy of LWIR Radiation Thermometers

Determining the size of source effect of a radiation thermometer is not an easy task and manufacturers of these thermometers usually do not indicate the deviation to the measured temperature due to this effect. It is one of the main uncertainty components when measuring with a radiation thermometer and it may lead to erroneous estimation of the actual temperature of the measured target. We present an empiric model to estimate the magnitude of deviation of the measured temperature with a long-wavelength infrared radiation thermometer due to the size of source effect. The deviation is calculated as a function of the field of view of the thermometer and the diameter of the radiating source. For thermometers whose field of view size at 90% power is approximately equal to the diameter of the radiating source, it was found that this effect may lead to deviations of the measured temperature of up to 6% at 200ºC and up to 14% at 500ºC. Calculations of the temperature deviation with the proposed model are performed as a function of temperature and as a function of the first order component of electrical signal.

Study on Intelligent Control of Laser 3D Rapid Prototyping Based on PMAC

The paper is based on industrial PC with rich application developed resources under Windows environment and openness of PMAC numerical control system. With the consideration of characteristics and specific requirements of laser rapid prototyping, a third party software is developed by Visual C++ in Windows98 to communicate with the slave machine to get some forming parameters in the laser processing under control by calling PCOMM32PRO DLLs which is offered by Delta Tau company. Combining the developed third party software with the infrared radiation thermometer monitoring the real-time temperature of molten pool can improve the forming efficiency of workpiece obviously.

Research on the Array Type Infrared Radiation Thermometer

In recent years, infrared temperature-measuring attracted more and more attention from home and abroad. Infrared temperature-measuring is non-contact and does not destroy the temperature distribution of the measured target object. At present, infrared radiation thermometer (point thermometer) and thermal infrared imager are wildly used. They both have advantages and disadvantages. The array type infrared radiation thermometer discussed in this paper contains the advantages of IR thermometer and thermal infrared imager and could measure the multi-point of the target’s surface simultaneously and accurately. Its basic principle is to obtain array processing to the infrared detector, simultaneously measure the multi-point temperature of the objects, take the measured object as a benchmark to calibrate infrared radiation thermometer so as to solve the problem of radiation rate fixed difficulties and improve accuracy of radiation temperature measurement.