Short answer: Greenhouse climate sensors should be placed where they represent crop conditions, protected from direct radiation, water and equipment exhaust, and checked against traceable references on a planned schedule. One sensor near a wall or control panel cannot represent a large greenhouse or multiple crop zones.
List temperature, relative humidity, radiation, carbon dioxide where used, wind, rain, substrate moisture, drain, tank level, EC, pH, flow and pressure measurements. For each sensor, state its control function, alarm use, range, accuracy, response time, environment and replacement plan. Avoid collecting data that no one reviews or uses.
Divide the greenhouse by compartment, crop, height, orientation, shading, cooling, heating and irrigation. A sunny edge, pad end, fan end, nursery bench and dense crop canopy can behave differently. Sensor quantity should reflect meaningful zones and risk, not a universal sensors-per-square-meter rule.
| Placement issue | Good planning practice |
|---|---|
| Direct sunlight | Use an appropriate shield or ventilated enclosure to reduce radiation error. |
| Crop height | Measure near the active crop zone and adjust as the canopy changes where needed. |
| Fans, pads and heaters | Avoid local discharge that does not represent the controlled zone. |
| Walls, doors and roofs | Keep enough separation unless the purpose is to measure that boundary condition. |
| Water and chemicals | Protect sensors and connectors from spray, condensation and corrosive exposure. |
Place the weather station away from roof exhaust, irrigation spray and local obstructions as far as practical. Confirm wind-sensor height and exposure, rain-sensor cleaning, radiation-sensor leveling and cable protection. Local specialists should review lightning and surge protection.
EC, pH, moisture, weight, drain and temperature measurements need representative sampling and crop-specific interpretation. One substrate probe may not represent every bag or slab. Define sampling positions, calibration solutions, cleaning and replacement. Keep sensor procedures consistent with the nutrient-management plan.
Calibration adjusts a sensor against an accepted reference where supported; verification checks whether readings remain within an agreed tolerance. Follow manufacturer procedures and keep reference instruments or solutions in suitable condition. Record date, result, adjustment, person and next due date.
Compare nearby or redundant sensors for unrealistic differences
Use range, rate-of-change and stuck-value alarms
Review readings against crop and weather observations
Inspect wiring, shielding, connectors and power supply
Check contamination, condensation and physical damage
Define a safe control response when a sensor fails
Maintain a sensor list with tag, model, serial number, location, range, calibration method, controller input and spare part. Show locations on as-built drawings. Keep critical spare sensors and compatible cables based on local availability and failure impact.
Base quantity on compartments, crop zones, climate differences, controls and risk rather than area alone.
Direct radiation can bias readings, so use suitable shielding and representative placement.
Follow manufacturer guidance, project accuracy needs, environment, drift history and operating records.
Use a documented safe fallback, alarm operators and prevent unsupported automatic action.
Use the intelligent control category, humidity guide and equipment data-sheet checklist.
Send the greenhouse zones, crop, systems and intended control points through the contact page for a sensor-list checklist.