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Pairs well with
The AC Infinity VPD Thermometer is an infrared laser thermometer that measures surface temperature instantly and calculates Vapour Pressure Deficit on the spot — the metric that tells you whether your plants are transpiring at the rate they should be. Point it at a leaf surface, pull the trigger, and get an immediate surface temp and VPD reading without touching the plant. For growers who optimise beyond basic temperature and humidity, this is the tool that closes the loop on environment management.
Specifications
- Target VPD of 0.8–1.2 kPa during vegetative growth and 1.0–1.5 kPa during flowering for most crops — these ranges support healthy transpiration without stressing the plant.
- Leaf surface temperature is almost always cooler than air temperature due to transpiration — always measure leaf temp, not air temp, for accurate VPD.
- Check VPD at multiple canopy positions — hot spots near lights and cooler zones near the floor can create significant VPD variation that a single wall-mounted sensor won't reveal.
How to Use
Pairs Well With
Continuous temperature and humidity monitoring alongside your VPD spot checks for a complete picture of your grow room conditions.
Humidity ControlHumidifiers and dehumidifiers to adjust RH after your VPD readings tell you where conditions need to go.
All AC Infinity ProductsControllers, fans, monitors, and tools for managing every aspect of your grow room environment.
Frequently Asked Questions
What is VPD and why does it matter?
VPD (Vapour Pressure Deficit) is the difference between the maximum moisture the air could hold and what it actually holds. It determines how hard a plant has to work to transpire — which affects nutrient uptake, CO2 absorption, and growth rate. Optimising VPD rather than just temperature and humidity individually gives growers more precise control over plant physiology.
Why measure leaf surface temperature rather than air temperature?
Leaf surface temperature is what determines the vapour pressure at the leaf — which is what matters for VPD calculations. Healthy, transpiring leaves are typically 1–3°C cooler than surrounding air due to evaporative cooling. Using air temperature alone gives an inaccurate VPD reading.
What VPD range should I target?
General targets for most crops: 0.4–0.8 kPa for seedlings and clones, 0.8–1.2 kPa for vegetative growth, and 1.0–1.5 kPa for flowering. These ranges support healthy transpiration without causing excessive water stress or stomatal closure.
Does this replace a standard temperature and humidity monitor?
No. This is a spot-check tool, not a continuous monitor. A fixed temperature and humidity monitor is still needed for ongoing environment tracking. The VPD thermometer complements it by giving you accurate leaf-level readings when you need to diagnose or fine-tune your environment.
Is VPD management only for advanced growers?
No. VPD is a more accurate way of understanding plant environment than tracking temperature and humidity separately — but the concept is simple to apply in practice. Once you know your target VPD range and have a way to measure it, adjustments to temperature and humidity become more intuitive and effective.
Point. Shoot. Know Your VPD.
AC Infinity VPD Thermometer — instant leaf surface temperature and VPD calculation for growers who want to optimise beyond the basics.