Optimizing Indoor Farming with Temperature and Humidity Sensors

Vegetable growing at any skill level can be a rewarding process, and while indoor agriculture is notably different from traditional agriculture, the underlying principles of hard work and constant attention continue to apply, particularly in terms of consistently maintaining the ideal conditions for plant growth.

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All elements of an indoor climate are relevant to optimizing vegetable growth, but two of these—temperature and humidity—are considered to be more important as their negative impact can be drastic.

Whether designing a climate control system for a smart greenhouse or a large vertical farming operation, temperature and humidity sensors are, therefore, essential.

This article looks at the different agricultural temperature and humidity sensor types, placements for both types, and how to source the best indoor agriculture sensors.

Agricultural Temperature Sensors for Indoor Agriculture

Temperature has a major impact on the growth and development of healthy, fruit-bearing plants in controlled-environment vegetable agriculture.

By maintaining precise control over the ambient temperature or the temperature of growing media, it is possible to:

• Optimize plant health
• Enhance growth rates
• Improve yields

This is no different from what happens in the natural environment, to a certain degree. For example, if temperatures reach extremes of hot or cold, or if temperatures place undue stress on a plant for an extended period, this can lead to crop underperformance or outright failure.

Proper temperature cycling, whether by mimicking natural patterns or implementing additional controls, is essential for minimizing the risk of plant diseases and molds.

Many different types of temperature sensors are employed in indoor farming, and designers of controlled environment systems typically choose between two types: NTC thermistors and RTD temperature sensors.

Principles of NTC Thermistors

NTC (negative temperature coefficient) thermistors are resistors whose resistance decreases as temperature increases.

NTC thermistors are made from semiconductor materials that change their resistance in response to temperature variations. Their high sensitivity to temperature changes makes them a popular choice for applications requiring precise temperature measurement and immediate control.

Their capacity to accurately monitor even subtle temperature changes makes NTC thermistors invaluable in maintaining the precise conditions required for optimal plant growth in indoor agriculture settings.

Principles of RTD Temperature Sensors

RTD (resistance temperature detector) temperature sensors work on the principle that a metal’s resistance increases with temperature. They leverage specific metals, like platinum, whose predictable change in electrical resistance increases as they are exposed to varying temperatures.

This enables precise, stable temperature readings across a wide range, making RTD sensors an ideal choice in helping maintain required conditions in indoor agriculture.

NTC Thermistors versus RTD Temperature Sensors

Both types of temperature sensors provide the same useful data for triggering climate control systems, but NTC thermistors continue to be the more popular option for several reasons.

Cost-Effectiveness

NTC thermistors tend to be less costly than RTDs, making them a more affordable option for indoor farming operations, irrespective of their size.

Ease of Deployment

NTC thermistors can be deployed more easily than RTDs. This is primarily due to their small size and flexible packaging options, which allow them to be more easily installed in different parts of an indoor farming setup, such as integration into irrigation systems or direct placement in soil.

Resistance-Based Measurement

NTC thermistors measure temperature changes through variations in resistance, which is particularly advantageous in the dynamic environment of indoor agriculture. Their high sensitivity allows for the detection of minute temperature fluctuations, providing greater control over the growing environment. This level of precision is crucial for optimizing plant health and growth.

Packaging and Versatility

With the right packaging, NTC thermistors can be adapted to a wide range of applications, such as monitoring air temperature or being embedded directly into the soil to measure root-zone temperature.

Humidity Sensors for Agriculture Indoors

Much like temperature, appropriate humidity is key to the success of indoor vegetable growth. When maintained within an optimal range, humidity levels can:

• Prevent plant dehydration
• Improve root growth
• Minimize the risk of fungal diseases

High humidity levels of over 80 % create the ideal environment for mold and other pathogens, but if humidity levels are below 30 %, plants will suffer from stress as they struggle to absorb water via their roots.

Types of Humidity Sensors for Agriculture

Several different types of humidity sensors are employed in indoor agriculture, but most indoor agriculture system designers typically choose between two options:

• Capacitive sensors: These sensors monitor changes in electrical capacitance which occur by the absorption of moisture, allowing them to detect humidity levels.
• Resistive sensors: These sensors measure humidity based on alterations in the electrical resistance of hygroscopic materials when exposed to moisture.

There is also a third, less-used option:

Thermal conductivity humidity sensors: These sensors are able to measure humidity by determining the air’s thermal conductivity, which changes with moisture content.

This measurement technique relies on the fact that air's thermal conductivity is variable and dependent on the amount of water vapor present. These sensors are a less popular choice for humidity measurement in typical HVAC or indoor agriculture applications due to their relative operational complexity and particular sensitivity to humidity changes.

Thermal conductivity sensors offer a unique approach to humidity measurements, but these are more specialized and may not be as convenient or as cost-effective as capacitive or resistive humidity sensors.

Capacitive versus Resistive Humidity Sensors for Indoor Agriculture

Capacitive sensors are the most popular choice in most cases because they offer several benefits.

• Improved accuracy and stability: Due to their specific functionality, capacitive sensors offer more precise and repeatable humidity readings.
• Longer lifespan: Capacitive types are designed for extended use without notable performance degradation, much more so than resistive sensors.
• Less prone to drift over time: Capacitive sensors can maintain their accuracy over longer periods, minimizing the need for regular recalibration.
• Reduced susceptibility to contamination: Capacitive sensors ensure consistent measurement accuracy because they are less impacted by chemicals, dust, and other contaminants.
• Long-term cost-effectiveness: Despite their potentially higher initial cost, capacitive sensors’ durability and minimal maintenance requirements make them a highly economical choice for indoor farming.

While resistive sensors’ lower initial cost reflects their relative simplicity, their greater susceptibility to contamination, lower accuracy, and tendency to drift over time make them less suited to the precise and consistent humidity control necessary in indoor agriculture applications.

Source: Amphenol Advanced Sensors

Sensors for Precision Agriculture: Livestock

Indoor livestock operations are significantly different from operations where produce is grown, but they still require robust, reactive agricultural sensors that can effectively monitor temperature and humidity.

Livestock, like plants, thrive in optimal indoor conditions within specific temperature and humidity ranges. Therefore, the sensors used in greenhouses can also be valuable in indoor poultry farms, helping to maintain the ideal environment for the well-being and productivity of the animals.

By carefully integrating temperature and moisture sensors designed for indoor agriculture into climate control systems, it is possible better to manage livestock from a number of key perspectives.

Health and Comfort

Excessive moisture or overheating can lead to stress, illness, or even death of livestock. At the same time, an environment that is too dry or too cold can have detrimental effects on animals’ well-being.

Disease Prevention

High humidity can promote the growth of parasites and pathogens that are harmful to livestock. Effectively managing moisture levels can minimize the risk of diseases, leading to a healthier livestock population.

Productivity and Growth

The maintenance of optimum environmental conditions can impact livestock’s growth rates, feed conversion ratio, and overall productivity. Animals tend to grow faster and produce more in a stress-free environment with ideal temperature and humidity levels, regardless of whether the end product is meat, milk, or eggs.

Ventilation Control

Sensors can help manage ventilation systems efficiently in livestock buildings, much like they do in indoor vegetable farming. Farmers can ensure their animals get sufficient fresh air by monitoring indoor air quality and adjusting ventilation accordingly. This is also key to conserving energy.

Waste Management

Farmers can better control the drying and handling of waste by monitoring moisture levels, helping to reduce odors and minimize disease potential.

Selecting the Best Sensor Temperature and Humidity Sensors for Indoor Agriculture

Controlled environments in indoor agriculture are both delicate and demanding. Replicating natural conditions is challenging, and artificial indoor environments require constant monitoring due to their ever-changing nature.

Data on every metric, such as soil moisture, must be both accurate and reliable. Additionally, indoor agriculture sensor technology needs to be environmentally robust to endure the conditions of a controlled setting while maintaining consistent performance over time.

When selecting temperature and humidity sensors for indoor agriculture, several factors should be considered:

• Accuracy: Humidity and temperature readings should be precise enough to maintain optimal growing conditions. It is, therefore, important to employ sensors with high accuracy ratings.
• Response time: Sensors must be able to rapidly respond to changes in temperature or humidity. This is especially important in the dynamic indoor farming environment.
• Durability and reliability: Sensors used in indoor agriculture must be able to withstand a diverse array of environmental conditions over the long term, including exposure to heat, moisture, and chemicals. Sensors should be constructed from durable materials and offer proven reliability.
• Cost-effectiveness: Cost plays a role in sensor selection for indoor agriculture operations of all sizes. Choosing high-quality sensors that provide the required accuracy and responsiveness while offering a competitive price is important.
• Packaging and integration options: There are several types of temperature and humidity sensors available, so it is important to consider the best options to meet specific application requirements.
• Connectivity: IoT agriculture sensors are an essential tool for modern indoor farming. When used in smart agriculture, these sensors integrate with control systems’ remote monitoring and control functionality, ensuring data-driven decisions and timely adjustments where required.

Sourcing the Ideal Agriculture Sensor Technology for Indoor Farming

Working directly with an advanced sensor manufacturer is the most ideal approach to selecting sensor technology. A good sensor manufacturer will have the technical expertise and experience to recommend the best sensor technology for a specific operation and its climate control systems.

The right sensor manufacturer can also develop customized solutions to meet the precise needs of an application, whether this is a greenhouse temperature sensor, a greenhouse humidity sensor, or an entire greenhouse sensor system.

Improving Indoor Farming

Farming techniques continue to evolve, and this field is becoming increasingly technology-driven.

The importance of robust and accurate temperature and humidity sensors in indoor agriculture cannot be overstated. Having the right sensors in place enables indoor farming operations to achieve greater consistency, precision, and efficiency in their climate control systems. This ensures optimal growing conditions and maximizes the effectiveness of the farming process.

These changes will ultimately lead to healthier livestock or plants and improved returns on investment.

Acknowledgments

Produced from materials originally authored by Amphenol Sensors.

This information has been sourced, reviewed and adapted from materials provided by Amphenol Advanced Sensors.

For more information on this source, please visit Amphenol Advanced Sensors.