Handheld Infrared Thermometers and Imagers in the Growroom

By Jeffrey Lebold
Published: July 4, 2022
Key Takeaways

There’s no doubt technology is now a huge part of any growroom. Infrared thermometers and imagers are useful devices that will help growers get quick and accurate temperature measurements resulting in healthier plants and a better yields.

Infrared temperature-sensing technology is not new. The mostly military developed technology has been used for years in weapons guidance systems, search and rescue, and industrial environments to detect heat sources from a distance. The infrared radiation emitted by an object, even if the object is cold, is in direct relation to the object’s temperature. Infrared thermometers and thermal imagers can detect the infrared radiation given off by an object and produce a very accurate temperature reading of the object without ever contacting it. The resulting benefit to the grower can be very quick, easy, and accurate temperature measurements that can really help gather useful information about your growroom.


Spot Thermometers and Thermal Imagers

Two types of thermal imagers. A low cost ($230 USD) thermal imager (left) and an even lower cost ($30 USD) infrared spot thermometer (right).
In general, there are two different types of handheld infrared temperature sensing instruments available. A spot infrared thermometer, the less expensive option, is capable of measuring the temperature of a spot location on an object. The thermometer is pointed at an object, a button is pushed and a temperature reading numeric value is obtained. You may have seen a spot infrared thermometer in use recently as they are commonly used to take temperatures of people to check for fevers.

An infrared thermal imager basically does the same thing, but an infrared image of the object is also obtained. Higher-end thermal imagers can save the thermal images for review. The temperature at any point within the thermal image can be measured. In addition to the more rugged stand-alone units, there are even options to turn your smart phone into a thermal imager.


Distance Matters

As you can probably imagine, the amount of infrared radiation measurable from an object decreases with distance. It matters how far away from the object the infrared thermometer or imager is held to obtain an accurate temperature reading. Some devices have a distance setting, some work with a fixed distance. If your device has a distance setting, ensure it is set correctly when taking each measurement. If your device works with a fixed distance, know what that distance is (it should be in the manual) and hold the device at the correct distance when taking readings. Measurements should always be taken perpendicular to the object being measured. Avoid taking measurements at angles.

What is Emissivity (E)?

Emissivity is a value (expressed between 0 and 1) that represents an object’s ability to emit and absorb infrared radiation. Dark surfaces such as asphalt or black paint have a high emissivity value while shiny or reflective materials like a mirror have a low emissivity value. If your infrared temperature measuring device has an emissivity setting, the setting must be set correctly to obtain an accurate temperature measurement of the surface. If your device has a fixed emissivity setting (typically around 0.9) measurements will be accurate with most objects, however, the reading may not be accurate when measuring low emissivity or reflective surfaces.

Do not let emissivity confuse or deter you from using the technology. In most cases around a growroom using your device with the “factory settings” will obtain accurate readings without even worrying about emissivity at all. If you are getting strange or obviously incorrect readings, especially when trying to measure the temperature of shiny or reflective surfaces, you may need to learn more about emissivity to obtain an accurate temperature measurement. Emissivity charts for many surfaces are available on the web. Pro tip: if you do have a highly reflective surface that you need to get an accurate temperature reading of and you are unsure of the correct emissivity value to use or your device has a fixed emissivity value of around 0.9, paint a small area of the reflective surface matte black or white. Take the measurement at the painted area. The emissivity value for matte paint is about 0.95.


Read also:

Some of the Many Uses of Infrared Thermometers in the Growroom

Foliage Temperature

The emissivity value for vegetation is around 0.95 so most all infrared thermometers will give a give an accurate reading of leaf temperatures. The temperature of your growroom is probably already known but what are the actual temperatures of the plant at the canopy or other locations? An infrared temperature measuring device is a great way to find out.


Lighting and Ballast Temperatures

photo of a thermal imager measuring a CFL bulb temperature.Photo of a thermal imager measuring a CFL bulb temperature.
How hot are my lights running? How much heat are my lighting ballasts adding to the growroom? Is one ballast operating hotter than the others? A quick point-and-measure with an infrared thermometer can tell you.

Pot and Root Temperatures

Outdoor plants in pots can get very hot sitting in the summer sun. Killing hot. The temperature of the roots in those pots should be monitored. Another great application for a non-contact measuring device.

Water and Reservoir Temperatures

Quick and accurate temperature readings can be obtained on liquids or liquid containers. Typically, a thermometer or sensor sits in the reservoir and growers already know the importance of monitoring the temperature there. A thermal imager or infrared spot thermometer allows you to determine the water temperature at any point in the system quickly and easily.

Air and Ventilation

The temperature of gases themselves cannot be measure with an infrared measuring device. However, a reading of a solid surface that will be close to the air or gas temperature can be measured to obtain a close estimate of air or gas temperatures. For example, ducting surface temperatures (if not a shiny surface) can be measured to determine the temperature of the air inside at any given point along the ducting.

Electrical Components

infrared image and photo example of an electrical hot spot.Infrared image example of an electrical hot spot.
While safety and caution should always be observed with electrical equipment, an infrared thermometer is a great way to determine circuit breaker, fuses, wiring, and other electrical devices operating temperatures.

Connection points for extension cords, lights and other electrical loads can be checked for operating hot spots without having to even touch the equipment. Fan and motor operating temperatures can also be obtained and monitored.

The spot type of infrared thermometers are very affordable and will neatly get most temperature measurement jobs done around a typical home growroom. The more expensive infrared thermal imagers may be a great asset to the larger commercial grow operations that require more thorough and recordable temperature data. As with all technology, infrared temperature devices must be used correctly.

Taking a little time to learn your temperature measuring device and practice with it will pay off in obtaining accurate temperature measurements that can expand your understanding of your growroom environment.


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Written by Jeffrey Lebold

Profile Picture of Jeffrey Lebold

Jeffrey Lebold received his first infrared thermographer certification in 1992 while working in the Ontario nuclear power industry. Since that time infrared thermography has become one of his passions and he established Boldstar Infrared Services Inc. in 1998, providing thermal imaging services to the Great Toronto Area while specializing in equipment reliability and building envelope assessment.

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