Chemical Dosing Control

Briefing

A chemical dosing system injects reagent into a water main proportionally. When flow is active and the operator enables dosing, the dose pump runs at a speed inversely proportional to the chemical tank level (smaller tank = more concentrated injection needed = faster pump speed). The dosing skid's VFD takes its speed reference directly from a proportional controller block in your program: declare DOSE_PID : PID and run it P-only so its CV equals (100 − TANK_LEVEL). A LOW_TANK_ALARM input cuts off dosing immediately and activates the LOW_TANK_LAMP warning.

Objectives

• DOSE_PUMP_RUN energises only when FLOW_RUNNING AND DOSE_START AND NOT LOW_TANK_ALARM
• Dose speed (DOSE_PID.CV, 0–100%) is proportional to (100 – TANK_LEVEL): emptier tank runs faster
• LOW_TANK_ALARM stops the dose pump and lights LOW_TANK_LAMP
• LOW_TANK_LAMP stays ON while LOW_TANK_ALARM is asserted
• When dosing is disabled or flow stops, DOSE_PUMP_RUN drops and the dose speed parks at 0

I/O Table

Your program will be tested against:

All test cases run automatically when you submit. Assertions are hidden until you pass.

1. #1Dose pump starts when flow active and dose enabled

   FLOW_RUNNING + DOSE_START + tank at 50% -> pump runs at ~50% speed

2. #2Dose pump stops when flow is lost

   FLOW_RUNNING goes false -> pump stops

3. #3LOW_TANK_ALARM stops dosing and lights lamp

   LOW_TANK_ALARM while running -> pump stops, LOW_TANK_LAMP on

4. #4Speed is inversely proportional to tank level

   Lower tank level -> higher pump speed