Analog scaling, alarms, quality and PID integration
Цель: Изучить тему «Analog scaling, alarms, quality and PID integration» и закрепить её практическими заданиями и самопроверкой.
2 акад. часа чтение и разбор теории, решение задач, работа со схемой или виртуальным стендом и проверка понимания.
Основной материал
A robust analog channel function block should do more than scale raw. It should handle input quality, bad signal, low/high engineering limits, filtering, alarm delay/hysteresis and simulation/manual override under controlled permissions.
Alarm hysteresis
High alarm 8 bar with deadband 0.2 bar: alarm triggers >=8.0, clears below 7.8. This prevents chatter around threshold.
Alarm delay
A 2 s delay may reject brief spikes, but must be justified. For safety-critical alarm, delay can be unacceptable.
Practical FB
AI_Channel inputs Raw, RawStatus, Range; outputs PV, Quality, HH/H/L/LL, Bad. This reusable block standardizes behavior across plant.
Практическая работа
Design AI_Channel specification for 0-10 bar, alarms HH 9.5, H 8.0, L 2.0, LL 0.5, hysteresis 0.2, filter 1 s.
Самопроверка
• Why analog block needs quality?
• What is alarm hysteresis?
• What is alarm delay?
• Why standard FB useful?
• When simulation must be controlled?
Что нужно запомнить
- A robust analog channel function block should do more than scale raw.
- It should handle input quality, bad signal, low/high engineering limits, filtering, alarm delay/hysteresis and simulation/manual override under controlled permissions.
- High alarm 8 bar with deadband 0.2 bar: alarm triggers >=8.0, clears below 7.8.
- A 2 s delay may reject brief spikes, but must be justified.
- AI_Channel inputs Raw, RawStatus, Range; outputs PV, Quality, HH/H/L/LL, Bad.