High-frequency PWM (pulse width modulation) temperature control device and control method for thermal analyzer

Abstract

The invention belongs to the technical field of thermoanalysis, in particular to a high-frequency PWM temperature control device and a control method for a thermal analyzer. The temperature control device includes a microcontroller module, a power control module and a temperature measurement module connected with a microcontroller respectively, an AC-DC voltage stabilization module and an interference rejection module connected with the power control module, and a heating wire connected with the interference rejection module; and the temperature measurement module further includes a thermocouple voltage measurement module and a cold junction compensation module. The AC-DC voltage stabilization module is used for converting AC to stable DC, and the power control module is used for receiving high-frequency PWM signals output by the microcontroller; and the microcontroller detects the thermocouple voltage and the cold junction temperature, obtains the actual temperature, and dynamically regulates the duty factor of the PWM signals output by the microcontroller. The invention further provides the control method suitable for the temperature control device, and can realize the high-precision temperature control required by the thermal analyzer.

Description

technical field [0001] The invention belongs to the technical field of thermal analysis, in particular relates to a temperature control device and a control method, in particular to a temperature control device and a control method suitable for a thermal analyzer. Background technique [0002] A thermal analyzer is an instrument that analyzes the relationship between certain physical and chemical changes and temperature rise and fall of a substance during heating or cooling. Commonly used thermal analysis instruments include thermogravimetric analyzer (TGA), differential thermal analyzer (DTA), differential scanning calorimeter (DSC) and thermomechanical analyzer (TMA). The above-mentioned instruments need to adopt the program temperature control method to achieve high-precision temperature control, including constant temperature heating / cooling, constant temperature, and even temperature modulation. The accuracy of temperature control directly affects the analysis results. ...

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Problems solved by technology

However, there is a disadvantage that power control is difficult to achieve higher resolution

If calculated according to my country's 50HZ mains electricity, if the power adjustment period is 10 seconds, the power control resolution can only reach 1 / 600

However, the heating rate of modern thermal analyzers ranges from 0.1 degrees per minute to 100 degrees per minute, and the rough resolution makes it difficult to achieve accurate temperature control.

The SCR conduction angle control method adjusts the power by changing the conduction angle, including trigonometric functions. To achieve linear power adjustment, the calculation of the conduction angle is very large, and the interference caused by the SCR control method is difficult to eliminate

In addition, for the above two temperature control methods, the fluctuation of mains power also has a great influence on the temperature control effect.

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