NQR spectrometer. Temperature control computerized system

The system described in this paper is part of a pulsed nuclear quadrupole resonance (NQR) spectrometer prototype. In order to record the dependence of NQR absorption frequencies upon sample temperature a thermostat system has been developed. The system maintains the sample temperature at a fixed value in the 5-25 deg. C range with an accuracy of ± 1 deg. C. The whole system is controlled by a computer. This feature is required by the specifications of the research project. The main guidelines of the software and hardware design are reported. A Peltier element is used to cool the metallic case which holds the sample. In order to prevent thermal and electrical overloads the system is equipped with protection circuits which disconnect the power supply and send warning messages to the user. A 10 bits A/D converter, two 8 bits D/A converters, 8 analog switches and a data buffer are containing by the hardware. The hardware can be connected to the parallel port of the computer or to one of ISA sockets. The software is a stand alone executable file that runs on Windows 95/98 platform and does not require the existence of another software package. A graphical interface allows to user an easy control over the sample temperature. All measured parameters by the interface are saved in a standard data file and can be processed further. The design is readily adaptable for other applications. (author)