Measurement Of Thermocouple Time Constant

In the field of industrial process control, temperature is a very important physical parameters. Because of the advantages, such as stable performance, simple structure, easy to use, accurate and reliable, wide temperature range, signal can be remote, the thermocouple in the field of industrial production and scientific research has become the most widely used in the sensing element. Testing requirements of the thermocouple time constant for the fast response thermocouple is important, help to understand the different response of the different packaging structures, during the response speed of more than thermocouples and test match ends in magnesium oxide thermocouples are widely used in providing.The paper is composed of two parts, which are the measurement system hardware design and software. The hardware is composed of four parts: sensors, signal amplification and sampling systems, STC microcontroller and PC processing systems, human-computer exchange system. The article on the various components of the system introduced in detail. With Visual Studio 2008 as development platform, software describes the use of single-exponential curve fitting the thermocouple temperature step response time constant of the curve to strike a new approach. This is the time constantτdefined as the theoretical basis, the measured thermocouple inserted into the boiling water from room temperature, after amplification and A/D sampled, then digital signal is sent from STC chip to the PC, the most optimized method of coordinate rotation method and conjugate gradient method for data processing, finding the thermocouple junction temperature rises to 63.2% of the entire step of the time required, and the fitted curve and the curve also shows the true response of the thermocouple tester interface supporting software, visually observing of the fitting results, and analyze the results of the fitting, obtained the best way to precision and repeatability.This article describes the method which adapt to the low sensitivity of the thermocouple and have some advantages, such as anti-noise ability, measurement accuracy, repeatability. The mechanical structure is a simple test, without the installation of photoelectric switches, you can test a variety of temperature sensor time constant. In tens of thousands thermocouples in the producing to export have been tested, the results show that quality control is very effective thermocouple.