Freezing Point Test System Design

Accurate measurement of the solidification point of the substance can be inversion of its molar mass and other parameters. Important in terms of product quality control, production and process control applications. Classic widely used measurement method is the method of the freezing point depression, within a certain range, it is possible to more precise measure the pure solvent, the impurity containing solution such as freezing point. This approach means summary, the procedure is more complicated, it is difficult to accurate measurement of large quantities. Computer-based control, using the principle of virtual instrument design high-precision measurement system, the mixing, heating, cooling, and automatic data logging and control process integration for the whole device, designed the test system of freezing point.The main contents of the test system of freezing point in this article include:(1) Based on the idea of virtual instrument, controlled by a computer, design solidification point test system hardware and software, including hardware control circuit and Labview-based virtual instrument control software.(2) Each part of the circuit of the control circuit board hardware. Mainly including Pt1000and Pt100three high-precision temperature measurement circuit design, based on the the agitation control circuit of the stepper motor, relay refrigeration control circuit and the heating compensation circuit.(3) Based on the design thinking of virtual instrument software control system, designing automatic alarm system, the completion of a software module on the the retarder temperature is the temperature of the water bath, stirring rate coordination control.(4) Debugging the test system of freezing point testing and calibration.The system test results show that the test system of freezing point can complete the real-time control of the various modules, to meet the experiment the main technical indexes and requirements, accurate measurement of the freezing point of the pure solvent (cyclohexane).