Definition
The collective magnetic thermostatic stirrer is a general laboratory equipment that integrates heating, constant temperature and magnetic stirring functions. It is usually composed of a heating bath, a magnetic stirring system, a temperature control system and a shell structure, which can achieve uniform mixing of liquids and precise temperature control in closed or open containers, and is widely used in experimental processes in non-medical fields such as chemical synthesis, material preparation, and biological sample processing.
Principle
The device works on the principle of electromagnetic induction and heat conduction. The magnetic stirring part drives the magnetic stirrer in the container to rotate synchronously through the bottom rotating magnetic field, which drives the liquid to form convection mixing. The thermostatic function heats the bath medium (such as oil or water) through the built-in heating element, and the temperature sensor and PID control algorithm maintain the temperature of the medium near the set value, and the heat is transferred to the sample through the bath wall and container. Its temperature control process can be simplified to a closed-loop feedback system where the temperature T is setsetand the actual temperature TactualThe deviation of e adjusts the heating power P through the controller, and the relationship can be expressed as: P = f(e), f is the control function. The stirring speed is adjusted linearly or stepwise by adjusting the motor input voltage or frequency.
Measurement method
Equipment performance evaluation should be measured according to relevant standards. Temperature accuracy measurements typically place a standard temperature probe in the bath temperature area to compare the deviation between the displayed value of the device and the standard value at different set points. For uniformity measurement, probes need to be placed at multiple points in the bath to calculate the standard deviation of the temperature distribution. The stirring stability can be measured by the optical tachometer and compared with the set speed. The heating rate can be calculated by recording the time it takes to rise from room temperature to a fixed temperature. Safety features include insulation resistance testing and overheat protection trigger point verification.
Influencing factors
Equipment performance is affected by a variety of factors. The heat capacity and fluidity of the bath medium affect the temperature uniformity and response speed. The material and shape of the container affect the heat conduction efficiency and stirring flow pattern. Ambient temperature and ventilation conditions may cause fluctuations in heat loss. The stirring effect is restricted by the shape of the agitator, magnetic strength and the flatness of the bottom of the container. Improper setting of control algorithm parameters can lead to temperature overshoot or oscillation. Aging of heating elements or media contamination after long-term use can also lead to performance degradation.
Applications
In the chemical field, it is used for catalytic reactions, polymer synthesis and other processes that require temperature-controlled mixing. used in materials science for nanomaterial preparation and sol-gel reactions; Used for sample preparation and extraction in environmental testing; The food industry is used for ingredient mixing and stability testing; Educational institutions are used to teach basic chemistry experiments. Its hermetic design is also suitable for experiments requiring inert atmosphere protection or volatile solvent handling.
Key points of selection
Technical parameters and experimental requirements should be comprehensively considered when selecting. The temperature range should cover the required range of the experiment and leave an appropriate margin. The volume of the bath should match the size of the commonly used container; The mixing torque should meet the requirements of medium viscosity. The control accuracy should be selected according to the sensitivity of the experiment. Safety features such as overheating protection and leakage protection are required. In terms of compatibility, it is necessary to confirm whether the equipment material is resistant to common chemical media. Energy consumption and heat dissipation design affect long-term operation stability. In addition, the user-friendly design and maintenance convenience of the user interface are also important considerations in actual use.