Accuracy
Calibrated before it leaves us.
Every Grow Sensor PRO is calibrated in our test chamber before it ships, light included, so every room is measured against the same reference. Below: how close each reading is, and what needs checking over time.
By Tom Starley, founder of Grow Sensor · updated
Spec sheet
How close each reading is.
Air, leaf, CO₂ and light each have their own sensor. Small numbers matter: at 26 °C, every 1 % of humidity error moves VPD by about 0.03 kPa.
| Channel | How it's measured | Range | Accuracy |
|---|---|---|---|
| Climate | |||
| Air temperature | Sensirion SHT45, digital | −9–58 °C | ±0.1 °C |
| Humidity | Sensirion SHT45, capacitive | 10–95 %RH | ±1 %RH (typical) |
| CO₂ | NDIR | 400–5000 ppm | ±(40 ppm + 5 %) |
| Plant | |||
| Leaf temperature | Infrared, read from the leaf | −30–100 °C | ±0.5 °C |
| Light | |||
| Spectrum | Multi-channel spectral sensor | 380–910 nm | ±2 nm a channel |
| ePPFD and ePAR | From the spectrum | 400–750 nm | Validated against Apogee |
| DLI | From ePPFD across the day | ±3 % | |
| Root zoneProbes carry their makers' published specs. They don't go through our chamber. | |||
| Water content | SubSense | 0–100 % VWC | ±1.8 % (0–50 %) |
| Pore water EC | SubSense | 0–20 dS/m | ±5–10 % |
| Substrate temperature | SubSense | −40–85 °C | ±0.5 °C |
| Water content | METER Group SOLYX 14 | 0.00–0.72 m³/m³ | ±0.03 m³/m³ (±0.01 medium-specific) |
| Bulk EC | METER Group SOLYX 14 | 0–20 dS/m | ±(5 % + 0.1 dS/m) to 10 dS/m, ±8 % above |
| Substrate temperature | METER Group SOLYX 14 | −40–60 °C | ±0.3 °C (0–60 °C) |
In the chamber
One chamber, every unit.
So when two rooms read differently, look at the rooms first.
- 01
Every unit, every channel.
Each Grow Sensor PRO goes into a dedicated test chamber before it ships: air temperature, humidity, CO₂, leaf temperature and light.
- 02
Light against a reference.
PPFD and PAR are calibrated in the same chamber and validated against Apogee, the quantum sensor growers benchmark against.
- 03
A record for every unit.
Each PRO has its own full calibration record, so the numbers it starts with are on file.
Under the lights
Built to read the air, not the lights.
Grow lights heat everything under them. A sensor that warms up reads the air too hot and too dry, and VPD reads high.
The PRO has no fan to fail, foul or bias the reading. Its case is passively cooled: a double wall with an air gap shields the sensors, like double glazing, and the shape draws cool air in through the base and lets heat out of the top.
Leaf temperature doesn't rely on the air at all. It's read by infrared, from the leaf.
Keeping it accurate
What needs checking, and when.
- CO₂Needs routine calibration. Sensitive to shock.
- Calibrate every 3 to 6 months, and after a drop. Outdoors in fresh air, started from the unit's button, in about two minutes.
- Temperature, humidity and lightDrift should be minimal.
- No routine calibration. Optional offsets for air and leaf temperature in the app. Check humidity against a Boveda 75 % kit only if a verified reference disagrees.
Step-by-step guides are on our help site.
Questions
What growers ask about accuracy.
Stop guessing. Start measuring.
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