EC and pH Monitor Over a Crop Cycle¶
Specification¶
The full specification below is extracted from Chapter 5: Nutrient Solution Chemistry and Mixing.
Type: microsim
**sim-id:** ec-ph-monitor<br/>
**Library:** Chart.js<br/>
**Status:** Specified
Purpose: Show students how EC and pH typically evolve over a full crop cycle in a recirculating DWC system, and let them simulate the effects of different management decisions (topping up water, adding nutrient, adding pH-Up/Down) on the curves.
Bloom Level: Analyze (L4)
Bloom Verb: Examine — students examine patterns in EC and pH data and identify when and why intervention is needed
Canvas layout:
- Top chart (55%): Dual-axis line chart over 35 simulated days: pH on left y-axis (range 5.0–7.5, optimal zone 5.5–6.5 shaded green), EC on right y-axis (range 0–3.5 mS/cm, target zone shaded light blue)
- Bottom panel (45%): Event log, day slider, and management action buttons
Pre-loaded simulation scenarios (dropdown):
- "Typical lettuce cycle — moderate drift" (pH rises ~0.2/day, EC drops as plants consume nutrients)
- "Hard water — buffered" (pH resistant to decline; bicarbonate causes slow upward drift)
- "Warm reservoir — rapid pH swing" (temperature-accelerated pH instability)
Management action buttons (apply at current day):
- "Add water (1L)" — decreases EC proportionally, pH unchanged
- "Add nutrient (10mL Part A+B)" — increases EC, slight pH change
- "Add pH-Down (5 drops)" — decreases pH by ~0.3 units
- "Add pH-Up (5 drops)" — increases pH by ~0.3 units
Interactive features:
- Day slider: Scrub through simulated days; chart updates to show current state
- Clicking "Apply Action": Records an event in the event log and updates the simulation forward
- Hover any data point: Shows exact pH, EC, and day values
- Red/orange zone overlays show when pH or EC is out of optimal range
- "Run to harvest" button: Fast-forwards the simulation to day 35 with no intervention — shows what happens without management
Event log: Text list of actions taken, date, and effect on EC/pH
Visual style: Green shaded band for pH optimal, blue band for EC optimal; red lines when out of range