WRE-620 WRE-621 WRE-622 WRE-542 WRE-543 assembly thermocouple, drocomputer control. The measuring instrument can automatically adjust the range and display the measurement result according to the resistance value of the measured resistance, and also has a resistance screening function. In the screening work mode, first enter the screening value and screening error through the keyboard. The measured resistance value is displayed during the measurement, and the screening value and screening error are displayed at the same time. After starting the alarm mode, if the measured resistance does not meet the screening requirements, a buzzer alarm will be issued.
Main technical indicators: Resistance measurement range 0 ～ 20MΩ, accuracy 1%. The resistance screening value and screening error can be set artificially, and will not be lost after power failure.
2. Key research content
This design includes hardware design and software design.
The hardware design mainly includes the single-chip microcomputer control system, signal conditioning and A / D conversion module, reference voltage generation circuit, range switching circuit, keyboard, LCD display module, alarm circuit, power supply, etc. The design difficulty is the generation of high-precision reference voltage and the range switching circuit.
Software design is mainly program design and debugging. Need to complete the system initialization, keyboard processing, resistance value measurement value calculation, resistance value display, screening value input and storage and screening error judgment. The design difficulty is the resistance measurement algorithm and the driving module of the liquid crystal display.
3. Implementation methods and methods
The design task is mainly completed through data search, design requirements analysis, overall system design, overall software and hardware design, detailed software and hardware design, system simulation and debugging, and data collation.