A modified version of a handheld automotive window-tint meter can estimate how much water a leaf holds without cutting or drying it. A peer-reviewed study published in August 2026 in Methods in Ecology and Evolution reports that this approach tracks leaf water status closely across six plant species in controlled experiments. Leaf water is linked to how readily vegetation burns, so the method could support wildfire-risk monitoring. It is a measurement proof of concept, not an early-warning system. The study does not show that the device predicts ignition, forecasts fire spread, or issues alerts.
What the device measures and how
The instrument is a Linshang Technology LS162A, a handheld meter designed to measure how much light passes through automotive window tint. The researchers kept the meter’s housing and detection electronics but replaced its light sources, so it measures transmitted light at two wavelengths: 940 nanometres and 1450 nanometres.
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The choice of wavelengths is what makes the device useful for leaf water. Water absorbs light strongly near 1450 nm, so a leaf with more water blocks more of that light. The 940 nm band is used as a reference, because water absorbs it only weakly. Leaf structure, such as thickness and cell arrangement, also changes how light passes through a leaf, and the reference band helps compensate for those differences. The study’s index is the logarithm of the ratio between the 940 nm and 1450 nm transmittance values.
What the modified build cost
The study lists the cost of each part at the time of purchase. These are study-era figures, not current retail prices, and the total excludes any labour for modification.
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| Item | Cost at time of purchase (GBP) |
|---|---|
| Linshang LS162A tint meter | £70.24 |
| Thorlabs replacement LED (first part) | £13.83 |
| Thorlabs replacement LED (second part) | £18.20 |
| Shipping | £14.50 |
| VAT | £23.35 |
| Total | £140.12 |
The paper names the replacement LEDs as the LED940E and LED1450E; the table above lists them in the order the study gives its costs. The University’s announcement rounds the modified build to about £140 and the original meter to about £70. The modification is a set of hardware changes, so an unmodified tint meter does not make leaf water or wildfire-risk measurements.
How the team tested the method
Step one: simulated leaves
Before touching a real leaf, the authors ran 1,000 simulations using the PROSPECT leaf optical-properties model, which generates the light response of modelled leaves across a range of structures and water contents. This step tested whether the two-wavelength ratio carried a usable signal in principle.
Step two: leaf dehydration experiments in 2026
The team then measured real leaves as they dried. The six species were winter wheat, rapeseed, beech, birch, hazel and sycamore. Each leaf was measured repeatedly during drying. Readings were compared with two reference measures: gravimetric equivalent water thickness (EWT), which is the mass of water per unit leaf area, and fuel moisture content (FMC), which expresses water as a proportion of dry mass. Both reference values come from the destructive weighing process described below.
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Across the tested species, the log of the transmittance ratio had strong relationships with both reference measures. The paper’s abstract summarises them as r² ≥ 0.85 for EWT and r² ≥ 0.81 for FMC. The more detailed results report root-mean-square errors (RMSE) of 0.05 or less for EWT and 0.79 or less for FMC.
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| Reference measure | Strength of relationship (r²) | Error reported (RMSE) |
|---|---|---|
| Equivalent water thickness (EWT) | ≥ 0.85 | ≤ 0.05 |
| Fuel moisture content (FMC) | ≥ 0.81 | ≤ 0.79 |
These figures describe how well the optical reading tracked the weighed reference values in these experiments. They are not a measure of how accurately the device would predict a fire.
Why leaf water links to wildfire risk
Dry vegetation burns more readily than wet vegetation, and fuel moisture is a standard input to fire-danger assessments. Leaf water status is related to both the combustibility of live vegetation and the moisture of the fuel that fire can reach. That connection is why the authors frame the method as a possible input to wildfire-risk monitoring. A reading of leaf water is one piece of information; it does not, on its own, describe weather, wind, slope, ignition sources or fuel loads across a landscape.
Limits to keep in view
Calibration is species-specific
The calibration functions differed among the six species, so a reading is meaningful only when it is converted with a calibration built for that species. The study does not provide a universal calibration, and it does not show that one exists.
Accuracy changes at severe dehydration
At very low water content the relationships became nonlinear. The authors suggest that severe dehydration can change leaf structure enough that the reference wavelength no longer compensates well. Readings from very dry leaves therefore need more caution than readings from moist ones.
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The evidence covers simulations and controlled drying
The study supports the method in simulations and in controlled leaf dehydration. It does not validate the device across wild vegetation, landscapes, seasons or operational fire-service use. Those settings would require further testing before the method could be relied on for decisions.
Destructive sampling compared with optical measurement
Conventional gravimetric sampling means collecting leaves, weighing them, drying them, and weighing them again. The paper describes this as the gold standard for leaf water, but it is labour-intensive and destroys the leaves measured. The optical approach takes a reading in seconds on an intact leaf, which allows repeated measurements on the same leaf during drying. Its trade-off is calibration: it depends on species-specific functions that must be established against weighed samples first.
Cost is the other axis. The study’s modified build was assembled for about £140. The study does not give a price for high-specification field instruments, so the cost comparison it supports is limited to the components it lists.
What the authors and the University say
The peer-reviewed article, Rapid non-destructive assessment of leaf water status with low-cost transmittance meters by Luke A. Brown and F. Mark Danson, was first published on 12 August 2026 (Methods in Ecology and Evolution, volume 17, issue 10, pages 2873–2880; DOI 10.1111/2041-210x.70388). Its abstract concludes: “Our results highlight the potential of low-cost transmittance meters, assembled using inexpensive and readily available components, for rapid non-destructive assessment of leaf water status.”
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- Accurate Soil Moisture Detection: The XLUX Soil Moisture Meter can tell you if the soil deep inside your pot or garden is dry, moist or wet; whereas your eyes and fingers can only determine the moisture level of the soil surface. The probe is 5.5 inches (14 cm) longer than regular styles, allowing it to measure the soil moisture at the bottom of larger and deeper flower pots.
- Easy-to-Read Large Dial: The large dial is easy to read and includes three zones with ten scales, making it very straightforward to understand.
- Immediate Moisture Reading: Insert the probe into the soil, and without waiting, the dial will immediately display the moisture level. You can then decide whether your plant needs watering based on the measurement. Do not leave this moisture meter in the soil for more than 5 minutes, as the metal tip will gradually corrode.
- Less Damage: A single probe causes less damage to plant roots compared to double or multiple probes, and when you remove the probe after testing, it won't bring out much soil.
- Usage Precautions: Do not use it to test very hard soil. Do not test water or other liquids. After testing, please wipe the probe clean.
In a King’s College London announcement dated 7 October 2026, Dr Luke Brown, Senior Lecturer in Earth Observation, linked the cost of instruments to who can make these measurements: “Environmental monitoring has long been rationed by the price of instruments,” says Dr Brown. “Bringing down that cost changes who is able to make these measurements, and that has potential to enable better management.”
The same announcement quotes Brown on the practical appeal of the method: “Water content tells you whether vegetation is healthy or ready to burn but previously to do this you had to destroy the foliage you are measuring. We wanted to show that a sensor cheap enough for any farm, fire service or classroom can do the job in seconds – and without damaging the leaf.”
Those statements describe the aim of the work. The paper’s own results, summarised above, are the evidence for what the method has shown so far.
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A Phys.org report dated 8 October 2026 covered the same study.
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