VEGETAL GROW DEVELOPMENT
Measure the horticultural light and adapt the LED lamps to your plants
LUZ SENSOR
The only connected spectrophotometer sensor providing real-time data on the quantity of light and quality of light applied to photosynthesis. Patented technology, the sensor analyzes each photon from 350nm to 800nm with a resolution of 1nm. It is designed to withstand the harsh environments of different growing media.
SPECTROphotoMeter - VIS
Portable instrument selected by the VGD expert team to carry out point spectrophotometric measurements in the visible. As part of light audits or to control the quality and intensity of the spectrum of your installation, the spectrophotometer is an essential tool for the agronomic traceability of a plant's growth process.
SPECTROphotometer - UV/NIR
Portable instrument selected by the VGD expert team to carry out point spectrophotometric measurements from UV (200-450nm) to IR (760-1100nm). New LED technologies make it possible to experiment outside the visible domain. This type of tool will allow you to quantify the specific light doses of your horticultural installation.
The advantages of horticultural light measurement
The importance of light for plant growth
Light is one of the most important factors for plant growth and development . Through the process of photosynthesis, plants convert light energy into chemical energy, thus fueling their growth. However, not all plants have the same light requirements, and precise light measurement is therefore essential to optimize their growth.
The benefits of measuring horticultural light
VGD's intelligent lighting technology and mastery of its light environment allows the optimization of its production tool, whether through energy savings, optimization of cultivation protocols, prediction of disease attack or analysis of shading and its impact on a crop.
The different types of horticultural light measurement
Light intensity measurement
Luminous intensity measures the amount of light emitted in a particular direction from a light source . This differs from the total brightness of a source, which takes into account the light emitted in all directions.
Light intensity measurement units
To measure light intensity, several units exist depending on the function corresponding to the measurement . The most common are: cd, lx, W/m², J/cm², and µmol/m²/s
How to measure light intensity in a horticultural environment
For measurements in horticultural environments, the primary measurement is the photon, which is measured in µmol/m²/s; W/m² is also used . Several types of sensors exist, each with its own specific characteristics and precision.
Light spectrum measurement
The light spectrum refers to the full range of wavelengths of electromagnetic light. The sun emits white light that can be broken down into different colors when passed through a prism. Each color thus obtained corresponds to a specific wavelength in the light spectrum.
The importance of the light spectrum in plant growth
The light spectrum is just as and even more important for plant growth than intensity. Depending on the spectral component received by a plant, its response can be different (for example, favoring the vegetative or generative aspect instead).
How to measure the light spectrum in a horticultural environment
The only method to measure a light spectrum in a horticultural environment is the use of a spectroradiometer. It allows data to be collected in W/m² per spectral band in nm. This data can be reprocessed to obtain the value in photons.
VEGETAL GROW DEVELOPMENT
Tools and equipment for measuring horticultural light
Light sensors and how they work
There are several types of sensors, each of which has its own specificity for measuring a quantity or even a quality of light. Luxmeters are mainly used to measure light for humans, pyranometers to measure solar irradiance useful for meteorology and PAR, ePAR sensors and spectroradiometers mainly for agriculture.
What is a light meter and how does it work?
A lux meter is a measuring instrument used to evaluate the intensity of visible light perceived by the human eye, called luminance. It measures the illumination of a surface in lux (lx). One lux equals one lumen per square meter.
Lux meters are commonly used in various fields such as indoor and outdoor lighting, industry, photography, and other applications where the amount of light is an important factor. They are often used to ensure that lighting levels meet recommended standards for specific human-related activities.
A pyranometer is an instrument used to measure solar irradiance, that is, the power per unit area from the sun on a horizontal surface . It is primarily used in meteorology, climatology, solar research, and solar engineering. The unit it measures is W/m² or J/cm², and the range over which the light is measured depends on the model.
The pyranometer measures total solar energy, including direct sunlight as well as diffuse light from the sky. It is designed to be sensitive to a broad spectrum of wavelengths, in order to capture all solar radiation.
The device generally consists of a sensor sensitive to sunlight, often a photovoltaic cell, surrounded by a glass dome. The glass dome allows light to reach the sensor while protecting it from weather conditions.
What is a pyranometer and how does it work?
What is a parmeter and how does it work?
A PAR (Photosynthetically Active Radiation) sensor, sometimes called a PPFD sensor, is a device designed to measure the amount of light available for photosynthesis in the wavelength range that plants use most efficiently . Photosynthesis, the process by which plants convert light into chemical energy to fuel their growth, occurs primarily in the visible light wavelength range, typically between 400 and 700 nanometers.
The PAR sensor measures the amount of light in this specific range, thereby providing an indication of the availability of light for the plant's photosynthesis process. These sensors are widely used in agriculture, ecology, plant research and horticulture to evaluate the light environment. The fact of not having an indicator on the quality of the spectrum, however, induces biased results if horticultural lamps are added.
A spectroradiometer measures the amount of light emitted or reflected at different wavelengths across the electromagnetic spectrum . It allows for the efficient measurement of both the quantity and quality of light, with accuracies down to 0.1 nm across the light spectrum. This means that for each nanometer of a spectrum, you can determine the number of photons received.
These instruments are widely used in various fields such as meteorology, remote sensing, astronomy, atmospheric research, and other applied sciences. Spectroradiometers are widely used in agriculture for varied applications including crop management, plant health monitoring, yield prediction and others.
With its ability to decompose the light spectrum, it is possible to convert W/m² into photons (µmol/m²/s).
It is the most precise sensor for analyzing light spectrum for plants but also algae and other living organisms.
What is a spectroradiometer and how does it work?
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VEGETAL GROW DEVELOPMENT
How to choose the light sensor for your crops?
Sensors to avoid
Lux meters should be avoided for measuring light absorbed by plants because this type of sensor is highly sensitive to the colors primarily seen by the human eye, which differ from those seen by plants . This type of sensor should absolutely not be used to measure professional horticultural LED lighting.
- Pyranometers make it possible to measure solar irradiance in W/m² globally between 200nm and 1000nm (see 2000nm for some). So this value is a fairly broad indicator of what is received in terms of energy, however it is linked to the full solar spectrum. Therefore, if horticultural lamps are added or if shade is provided modifying the light spectrum of the sun, the values are no longer relevant.
- PAR and ePAR sensors give values in photons (µmol/m²/s) between 400nm and 700nm (750nm for ePAR). However, the value given may include unreliable areas of data which distort the quantity of photons actually perceived.
The measured value is only quantitative, it is global and without indication of the quality of the spectrum.
The representations above allow the highlighting of sensor response errors at different wavelengths. It can be noted mainly that a PAR sensor can give very unreliable results depending on its relative response to photons, especially when the spectral analysis is based mainly on red and blue wavelengths.
Sensors to watch out for
The most reliable sensors
Today, spectroradiometers that convert received light energy into photons are the most reliable sensors . The resulting measurements are quantitative and linked to spectral quality because each wavelength has a different conversion rate.
VGD has developed an integrated spectroradiometer that converts the light spectrum into photons, enabling data recording and processing according to plant needs . It is possible to target the spectra absorbed by chlorophylls a and b (or other photopigments) and photoreceptors.
VEGETAL GROW DEVELOPMENT
Interpreting horticultural light measurement data
Ideal values for plant growth
There are no miracle values but some general rules that can emerge.
Ideal light intensity values for different plant growth stages
In general, we can give a few metrics, however they may vary depending on the plant species you are working on:
- In vitro culture: 70 µmol/m²/s
- Seedlings/Cuttings: 100 µmol/m²/s
- Growth: 150-250 µmol/m²/s
- Flowering: 300-400 µmol/m²/s
These values are indicative and each project requires a case study to define the need and how to meet it depending on the production systems and the type of plant or species targeted.
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VEGETAL GROW DEVELOPMENT
Using measurement data to optimize horticultural lighting
How to use measurement data to adjust lighting in a greenhouse or grow room
Accurately collecting light data allows for precise management of LED lighting in horticultural crops, tailored to the plant's needs and stage of development. Using inaccurate data or data with a high error rate can result in plants receiving unsuitable light (either too much or too little). At VGD, we have tested numerous sensors since our inception, and light measurements involving LEDs in agriculture can vary significantly depending on the sensors used.
With good measurement, it is possible to control HPS or LED lighting according to weather conditions and the objectives sought for the culture. Real-time intensity adaptation is possible by looking at precise spectral bands that are important to the plant.
With the sensor developed by VGD, it is possible to record data in spectral bands to refine the LED control system . It is also possible to compile the results over several seasons to review the data and look for correlations between various parameters (temperature, humidity, light, etc.) and an associated agronomic outcome.
Common mistakes to avoid when interpreting measurement data
Light data in a growing environment is very important because it is part of all the parameters measured. By correlation, monitoring of the development of culture is facilitated. However, like any correlation each error added by a parameter will result in a larger error in the end. It is therefore crucial to work with as much accurate data as possible.
Our answers
The amount of light depends on the stage of development of the plant. Generally speaking, the light should gradually increase as the plant develops.
The different parameters to take into account when measuring light in horticulture are the positioning of the sensor, the measurement integration time and everything that revolves around data recording times in order to be able to output the best data .
Commonly used units for measuring light in horticulture are µmol/m²/s. This unit makes it possible to measure the number of useful photons captured by the plant. We can also find W/m² but this unit can only give an indication if we measure the solar spectrum without modification.
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