Conclusiom

Temperature measurement is an integral part of many process industries. Thus it is essential to have a competent system for this measurement purpose. We deals with the design and implementation of a Personal Computer (PC) based, temperature measurement system. The main sensor used in this case is a commercially available thermistor and custom-made signal conditioning hardware and a data acquisition system. The distinct advantage of this system is its cost effectiveness when compared with conventional temperature measurement systems frequently employed various processes. The thermistor output is a single ended voltage, which is dependent on the transfer function of the thermistor itself. According to this transfer function, the thermistor provides a certain voltage for a certain temperature. The output of the thermistor is then amplified using a non-inverting instrumentation amplifier. Then the instrumentation amplifier output signal is fed to an Analog-to-digital converter (ADC) that will provide digital output. Then output of ADC is connected to a multiplexer which convert digital data from parallel to serial. Finally, this digital information is sent to a Personal Computer (PC) directly via the standard parallel port. Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range. From thermistor characteristics ,it is non-linear but we use it because of its sensitivity of temperature. Among of temperature sensor it is most sensitive. Non-linearity can be minimized by hardware or software compensation.
 

we have tried to build up concepts over the major components of our project. But, we want to recommend that the theoretical knowledge is not all in all. The components may not work properly, the connections may be lost anywhere and hazards may come eventually. So, troubleshooting is always required without losing temper. Works with parallel must done with care. If two line of port is short circuited that can burn out motherboard of the computer. For this first we find out each line of by short circuit test. Applying input to port vary carefully, to avoid electrical hazard. We do the work for design purpose, for this measurement is not so accurate. Working with of op amp biasing voltage applied carefully and all the measurement done across the point and system common.