Using PAR Meters and Sensors For Plant Growing

We know from experience how much light should be provided to various plant types to maximize their growth. These light levels vary based on the plants age and sensitivity to light. 

Using PAR Meters and Sensors For Plant Growing

PAR meters are an important tool for growers and they provide useful data about the total amount of photosynthetic light being transmitted to the sensor. 

LUX or Light meters on the other hand, which are far cheaper, provide data about the total amount of visible light being transmitted to the sensor. 

To understand the true value of a PAR meter versus a LUX meter it is important to understand how photosynthetic light differs from visible light. Plants "see" light differently than humans do. Studies have shown that plants benefit from light wavelengths between 400 to 700 nanometers. Visible light on the other hand includes more wavelengths from 380nm to 740nm. When measuring photosynthetic light those extra wavelengths above 700nm and below 400nm are excluded. 

PAR is measured using a specially calibrated sensor which measures quantum flux. Quantum flux is the amount of photosynthetic light hitting the sensor and is displayed in UMOLs/ms. Reading a PAR meters screen will display the total amount photosynthetic energy and can be interchangeably called PAR (photosynthetic active radiation), or PPFD (photosynthetic photo flux density). Both terms means the same thing relative to reading PAR meters. 

There is a third measure which can be confusing when comparing a grow lights energy output. Many manufacturers will advertise a term called PPF. PPF (photosynthetic photon flux) is a laboratory measurement. It has very little to do with the amount of PAR or PPFD that a PAR meter will read. Higher PPF numbers do equal higher amounts of potential light output but it can also be misleading based on the lights total shape and size. 

It is best to focus on PAR/PPFD because that is the amount of valuable light the plants are receiving. 

We know from experience how much light should be provided to various plant types to maximize their growth. These light levels vary based on the plants age and sensitivity to light. 

Cannabis for example has several life stages. The seedlings/clones stage when plants are delicate and sensitive to high PPFD levels, vegetative stage when the plants are fully rooted and building size and the reproductive or flower phase when the plants mature and finish their growth then die. 

Generally speaking here are the correct light levels for each stage:

  • Seedlings or clones which are newly sprouted or planted: 100 umols/ms PPFD +/- 20
  • Rooted clones/young veg plants: 250 umols/ms PPFD +/- 50
  • Vigorous veg plants: 350 umols/ms PPFD +/- 50
  • Reproductive/flowering plants (not using supplemental CO2): 750 umols/ms PPFD +/- 100
  • Reproductive/flowering plants (supplemental CO2 of 1200ppm+): 1000 umols/ms +/1 100

These numbers are guidelines and not to be considered the only factor when evaluating plant health relative to light levels in your grow space. As a side note, PPFD decreases by about 50% over distance. So reading PAR/PPFD at 24" from your light will decrease to about half if you move the meter 48" away. Because PAR meters use quantum light measurement the inverse square law does not apply. 

A growers experienced eye is an important addition to the mix. Plant health depends on hundreds of potential variables. But we do know from experience that when the inner most sets of new leaves are pointing directly up towards the light that the plant is happy with the level of light it is receiving. Drooping, wilted, yellowing or veining are signs of stress which may or may not be from the light being provided. 

One thing to note about PAR levels is that spectrum is not being measured or considered. And spectrum does effect plant structure, growth and potency. 

PAR meters will read the total amount of light regardless of the color of light being produced. So one way of looking at that is if you had solid orange diodes the PAR meter would be displaying the total amount of energy in just that range of color. Narrow spectrum Blue/Red diode mixes, sometimes called "burple" also display the PAR/PPFD energy total. And with full spectrum LEDs which produce a lot of bright white visible light, the PAR meter is reading the sum total of all of the photosynthetic light being produced.

In all cases the meter is cutting off light wavelengths below 400nm (ultraviolet) and above 700nm (infrared). Different instruments are required to read those wavelengths or an extended range PPF quantum sensor can be used. The light levels above would not apply to the extended range and would be higher. 

PAR meters are an important tool for any grower. HID lights like HPS and MH have short bulb lives. The amount of PPFD will decline over time based on the  number of hours the light has been operating. The light may appear bright, and it might even read high on a LUX meter but the PAR output is steadily declining. 

Using a well made PAR meter which can read full spectrum PPFD is a tool which will pay off over time with healthy plants through each phase of growth. 







Premium Quality For Growing

More Products

Sold out -6% sale
Trolmaster HCS-2 Hydro-X Pro Control System
Trolmaster HCS-2 Hydro-X Pro Control System $ 2,374.00 $ 2,499.00
  10.1' Touchscreen Fully Customizable  Free Smart Phone App plus Web-base control system TrolMaster revolutionized environmental controller technology when it introduced the Hydro-X. The Hydro-X Pro continues the revolution with a 10’ touch-screen and a web-based software. The Hydro-X Pro is backwards compatible with all current Hydro-X control / device modules. It also provides greater flexibility and allows any plug-in module to be addressed to be whatever the user wants. The user can also set up each plug-in module to have multiple “conditions” that will activate the module, allowing for almost unlimited control options. The Hydro-x Pro is designed to be a single room controller for reliability and ease-of-use. The Hydro-X Pro expands the capability of the original Hydro-X by allowing up to 50 sensors and up to 50 separate control modules to be connected to a single Hydro-X Pro. Multiple sub-zones can be created within the single grow space by linking a specific sensor, to a specific control function(s).The new 4-in-1 sensor comes with a LCD screen which provide the ease of onside monitoring. Customized programming allows almost limitless degree of control. Each of the variables (Temperature, Humidity, CO2, Light) can be controlled independently, meaning a customized ramp-up / ramp-down can be used to closely simulate natural outdoor conditions, or simply allow complete customization of the environment. Displayed on an easy-to-read and construct “graph” it allows the user to have 100% control of their environment. Another powerful feature of the Hydro-X Pro is the built-in calendar and calendar presets that allows the user to schedule an entire crop’s “recipe” within the Hydro-X Pro. All settings including Lighting, Temperature, Humidity, CO2, and Timers can be specified by the user as they “build” their multi-week crop schedules. Reminders can also be programmed to ensure critical tasks are not forgotten. The TrolMaster APP will also allow for notifications with separate day/night limits to be received by the user. The web-based software provides easy access and more advanced remote control. Onboard data acquisition and the ability to store and share setting between multiple devices, means that user-defined programs & settings can be saved and loaded into multiple Hydro-X Pro units with ease. A personalized screensaver page can be uploaded through a USB port. The same upgradeable feature like Hydro-X gives you the ability for life-time improvements. Included: 1x HCS-2 Controller 1x MBS-Pro Sensor 1x Mounting Plate 1x RJ12 Cable Set
-1% sale
TrolMaster Hydro X Plus HCS-3 Grow Room Controller
TrolMaster Hydro X Plus HCS-3 Grow Room Controller $ 1,195.00 $ 1,199.00
The Hydro X Plus / HCS-3 system is a professional-grade single-zone environmental control system that can control your entire grow space. It has an 800x480 7” LED display monitor and can control an unlimited number of lights, 8 temperature devices, 8 humidity devices, 4 CO2 devices, and 12 programmable timer devices (up to 50 schedules can be created). With incredible flexibility and the expanded product capacity, anyone can now easily customize their own grow room control system for maximum yields. Having multiple control modules also provides the option for the user to create multiple "stages" of growth. By staggering the start times of each stage, the user can minimize the amount of time that plants spend in vegetative growth and focus on the flowering phase. Having multiple control modules also provides the option for the user to create multiple "stages" of temperature and humidity control, which will provide a more stable environment. The HCS-3 system comes with an MBS-PRO 4-in-1 sensor to measure temperature, humidity, CO2 ppm, and the presence of light. Lighting control has never been easier or more capable. The optional MBS-PAR light sensor can be added to the system. It will automatically adjust light intensity to precisely provide the exact amount of illumination for optimum plant growth. The Hydro-X Plus has been can also track your DLI levels. Having 2 separate lighting control channels allows the user to create multiple lighting layouts (and dimming sequences) based on their individual preferences. Besides controlling your room, if a problem is detected by the HCS-3, a warning message (notification) will be sent to your smartphone. Up to 10 smoke detectors and 10 water leak-detectors can be connected to the HCS-3 which will alert you if there are any fire or water leaks. The HCS-3 also offers multiple advanced functions to control your entire grow room or greenhouse such as Sunrise / Sunset simulation, DLI control, overheat protection, Spectrum & Group lighting control, and more.  
Sold out -6% sale
Trolmaster MBS-PAR Quantum Sensor for Hydro-X Pro
Trolmaster MBS-PAR Hydro-X Full Spectrum Quantum Sensor $ 417.95 $ 442.00
The Full Spectrum Quantum Sensor (MBS-PAR) provides accurate and cost-effective measurement of photosynthetically active radiation (PAR) from all light sources used to grow plants. The full-spectrum quantum sensor has a spectral range of 389 to 692 nm ± 5 nm. The improved spectral response increases the accuracy of LED measurements. 
Sold out -6% sale
Trolmaster MBS-Pro Quantum Sensor for Hydro-X Pro
Hydro X SuperstoreTrolmaster MBS-PRO Hydro-X Temp/Humid/CO2/Light 4-in-1 Sensor for Hydro-X Pro $ 377.95 $ 399.00
The MBS-PRO 4-in-1 sensor combines a precision air temperature, humidity, CO2 (PPM) sensor and photocell to create the perfect all-in-one environmental sensor. It is designed for Hydro-X Pro system only.  Assembled using a new water-resistant plastic injected enclosure, the MBS-PRO can be placed in multiple locations throughout the growing area to provide spot measurements from multiple sensors (Up to 50 sensors can be connected to the Hydro-X Pro) The sensors can then be used together (averaged) or separately in order to control a specific section of the grow area by assigning a sensor to a specific control device. The MBS-PRO features a built-in LCD display to show the current conditions of that sensor which provide the ease of onsite monitoring. It also features a new “push-lock” connection to make installation easy.Please Note: The MBS-Pro requires the SPH-1 for supplemental power. "Sensors should remain dry and clean to prevent premature failure. Do not spray foreign substances or allow water / condensate on the sensors"  
-9% sale
TrolMaster HCS-1 Controller w/3-in-1 Sensor Bundle
TrolMaster HCS-1 Controller w/3-in-1 Sensor Bundle $ 299.95 $ 329.00
If you're looking for a complete, professional-grade environmental control system, the TrolMaster Hydro-X is the perfect solution. This modular system is easy to install and expand, and can be fully customized to your needs. With the free TrolMaster App, you can access all system settings and alerts from anywhere, anytime. The Hydro-X system is compatible with most grow lights brands, HVAC systems, mini-split air conditioners, commercial dehumidifiers and humidifiers, as well as CO2 generators or regulators. So whether you're looking to maintain optimal growing conditions in your indoor garden or keep your home comfortable all year round, the Hydro-X system has you covered. Includes the TrolMaster 3 in 1 sensor bundle and RJ16 cables. A turn-key environmental sensor system to tune up your gardens success.  Looking for a trusted high volume TrolMaster Official Distributor in North America? Look no further than Forever Green Indoors! We're the leading provider of quality TrolMaster products and accessories, and we're here to help you keep your indoor spaces looking their best.We've got everything you need to keep your plants healthy and green, from TrolMaster controllers and sensors to PAR meters and EC sensors. And we're always happy to offer advice and assistance to make sure you get the most out of your TrolMaster products.So if you're looking for top-quality TrolMaster products and accessories, plus expert advice and support, come to Forever Green Indoors - we're your one
-5% sale
Trolmaster MBS-S8 Hydro-X CO2 Sensor - Accessory for HCS-1 Controller
Trolmaster MBS-S8 Hydro-X CO2 Sensor - Accessory for HCS-1 Controller $ 210.90 $ 222.00
 Description The optional CO2 Sensor (MBS-S8) measures the CO2 PPM within the growing area. Using the MBS-S8 allows the users to connect and control their supplemental CO2 system using the Hydro-X. *Used in combination with one or more DSC-1 CO2 device modules.
-5% sale
Trolmaster  4RS-1 4 Outlet Expander Station
Trolmaster 4RS-1 4 Outlet Expander Station $ 137.75 $ 145.00
The 4RS-1 is a universal 4-outlet power expansion module. It can be used with any of TrolMaster’s “plug-in” style device modules to expand the number of devices that can be controlled by the Hydro-x. A single 120-240 volt “trigger” cable on the 4RS-1 connects to your device / control module. When the device module is activated by the Hydro-x, the 4RS-1 trigger cable will turn on each of the 4 receptacles on the 4RS-1 with a 3 second time delay between each outlet being activated. That minimizes high start-up (inrush current) and allows up to 4 devices to be safely controlled. The 4RS-1 must be installed with a 120/240 volt power circuit (up to 50-amps @ 240vac). Three wire terminals inside the unit accept up to #6 AWG wire making connections to the power source easy.
5% sale
TrolMaster TSH-1 Temperature / Humidity Station
TrolMaster TSH-1 Temperature / Humidity Station $ 122.50 $ 116.38
  The Trolmaster TSH-1 Temperature / Humidity Station is a 0-10 volt analog output control station that works with the HCS-1 and HCS-2 controllers. The TSH-1 can be configured to control either a temperature or a humidity device that requires a variable 0-10 volt input signal. The TSH-1 is capable of controlling variable speed fans, vents or any other device that accepts a 0-10 volt input. It features separate day and night “idle” speed settings built-into the TSH-1 as well as separate Day / Night setpoints accessed through the HCS controller.





(Orders before 11am pst)