Humidity sensors for fruit storage: reliable measurement in high humidity and condensation conditions

Author: T. Graf

We’ve explained here why high-humidity sensors are crucial in demanding environments and what challenges arise when the air is nearly saturated (> see the article on high humidity: AFTF 35 / KFTF 35).

But what does this look like in practice?
Fruit storage facilities present a particularly demanding application: Here, temperature fluctuations and high humidity quickly lead to condensation—which directly affects measurement accuracy and storage quality.

In this article, we’ll show how these challenges can be reliably overcome in fruit storage facilities—and what role specialized sensor technology plays in this process.

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In a nutshell

Fruit storage facilities are characterized by low temperatures, high relative humidity, and frequent changes in operating conditions. It is precisely this combination that makes humidity measurement challenging: Condensation can form when doors are opened, when goods with higher product temperatures are stored, or when air currents are present. Conventional humidity sensors often respond slowly in such situations or provide unstable readings.

Condensation-protected humidity and temperature sensors, such as the AFTF-35 and KFTF-35, are designed for such applications. They support stable climate control, help prevent quality losses, and provide reliable measurement data for warehouse systems, building management systems (BMS), or distributed control systems (DCS).

Typical applications include apple storage facilities, CA/ULO storage facilities, vegetable storage facilities, ripening rooms, temporary storage facilities, and cold storage facilities with frequent inventory turnover.

Contents

Common Challenges in Fruit Storage What metrics are important in a fruit storage facility? AFTF-35 vs. KFTF-35 – Which design is best suited for fruit storage? Installation Instructions for Humidity Sensors in Fruit Storage Facilities Integration with Building Management Systems (BMS), DDC, and Warehouse Technology Choose the right humidity sensors for your fruit storage facility now

Why Moisture Measurement Is Critical in Fruit Storage Facilities

Fruit storage is not just about maintaining a certain temperature. The key factor is the interplay of temperature, relative humidity, air movement, and storage duration. If the air is too dry, the stored produce loses Humidity. This can result in weight loss, shrinkage, and reduced marketability.

If, on the other hand, the air is locally saturated or if temperature fluctuations cause the temperature to fall below the dew point, condensation occurs. This condensation can form on sensors, surfaces, packaging, or directly on the stored goods. This is critical for control purposes because the measured humidity value then no longer reliably reflects the actual indoor air conditions.

Reliable humidity and temperature measurement therefore supports not only climate control but also quality assurance, energy efficiency, and process reliability in warehouse operations.

Why Traditional Humidity Sensors Have Their Limits in Fruit Storage Facilities

Traditional humidity sensors work reliably as long as the sensor surface remains dry and environmental conditions are stable. In fruit storage facilities, however, these conditions are not always met. High humidity, cold surfaces, and rapid temperature changes increase the risk of condensation forming on the sensor element.

As soon as a film of water forms on the sensor element, the sensor no longer measures the ambient humidity but enters a state of measurement distortion. This can result in sluggish readings, longer recovery times, or erroneous control signals.

Condensation-protected sensor technology reduces this risk by operating the sensor element at a controlled temperature slightly above ambient temperature. This keeps the sensor surface drier and the measured value more stable—even during periods of high humidity.

Common Challenges in Fruit Storage

In practice, the most critical situations rarely arise during stable, continuous operation, but rather during changing operating conditions. It is precisely then that the sensors must provide reliable readings.

Gate Openings and Cargo Handling: When doors are opened, warmer and more humid air enters the cold storage area. As this air cools, the relative humidity rises rapidly. If the temperature drops below the dew point, condensation may form.

Storage of Warm Goods: Freshly stored fruit introduces heat and moisture into the storage room. This creates localized climate zones that only gradually even out.

Airflow and Stacking: Conditions among boxes, pallets, and shelves may differ from those in open space. The sensor's position therefore directly affects the accuracy of the measurement.

Defrosting and Cleaning Processes: Technical operating conditions, such as defrost cycles or cleaning phases, can also cause short-term spikes in humidity. A suitable sensor system must be able to withstand such phases without drifting over the long term or failing.

What metrics are important in a fruit storage facility?

When it comes to climate control in a fruit storage facility, it is not just individual measurement values that matter, but how they interact. Temperature fluctuations, in particular, can quickly change the relative humidity and increase the risk of condensation.

Key metrics include:

  • Relative humidity—a key control parameter for the storage environment
  • Temperature – directly affects how much moisture the air can hold
  • Dew Point – Helps Assess Condensation Risks
  • Absolute humidity – indicates the actual water content of the air
  • Mixing Ratio – Helps Evaluate Ventilation and Dehumidification Processes

The AFTF-35 and KFTF-35 measure humidity and temperature and can provide additional calculated parameters for building automation systems, distributed control systems, or warehouse technology. This allows not only for the regulation of the warehouse environment, but also for its more accurate assessment.

AFTF-35 vs. KFTF-35 – Which model is best suited for fruit storage?

Depending on the system, both room sensors and duct sensors can be used in fruit storage facilities. The key factor is where the measured value is needed for control purposes:

AFTF-35 (Surface-Mounted Sensor)

  • Wall mounting in rooms
  • Ideal for warehouses and cold storage rooms
  • Direct measurement of indoor air

Typical applications: Cold storage facilities, fruit storage facilities, vegetable storage facilities

The AFTF-35 is suitable for direct measurement of the ambient air in storage areas. It is typically installed on a wall or mounting surface and provides readings at the location where the storage environment is to be evaluated or controlled. It is important to choose a location with representative airflow—not directly at the door, not immediately next to the evaporator, and not in dead zones behind stacks.

KFTF-35 (Duct Sensor)

  • Installation in Air Ducts
  • includes mounting flange
  • for ventilation and air conditioning systems

Typical applications: Supply air/exhaust air measurement, HVAC systems, centralized humidity control in (food) processing facilities and the pharmaceutical industry

Both provide standard signals and can be easily integrated into GLT/DDC.

Our KFTF-35 is used in ventilation or air-conditioning ducts. It is ideal when humidity and temperature measurements need to be taken in the supply or exhaust air, for example in central ventilation units, recirculation systems, or systems with controlled air treatment.

Installation Instructions for Humidity Sensors in Fruit Storage Facilities

The measurement point in the fruit storage facility should be selected so that it provides as representative a picture as possible of the actual storage environment. When AFTF-35 It is recommended to choose an easily accessible location with sufficient airflow—not directly by the door, not in the immediate cold airflow from an evaporator, and not in areas with poor airflow behind stacks of merchandise.

The KFTF-35 is referred to as Duct sensor Installed in ventilation or air conditioning ducts using the supplied mounting flange. Before installation, ensure that the measurement range, installation length, duct dimensions, flow velocity, and protection class are suitable for the application. A maximum air velocity of 30 m/s is specified for the KFTF-35.

Important: The AFTF-35 and KFTF-35 are designed for high-humidity environments; however, according to the operating instructions, they are intended only for use with non-polluted, non-condensing air without positive or negative pressure at the sensor element. Installation and commissioning must be performed only by qualified personnel. For the specific installation, always follow the instructions in the operating and installation manual.

Integration with Building Management Systems (BMS), DDC, and Warehouse Technology

The AFTF-35 and KFTF-35 humidity and temperature sensors can be easily integrated into existing BMS, DDC, or warehouse management systems using standard signals. Depending on the model, active outputs of 0–10 V or 4–20 mA are available. This allows relative humidity, temperature, and an additional calculated parameter to be transmitted directly to the control system.

This is particularly helpful in fruit storage facilities because climate control does not rely solely on a single humidity value. Depending on the settings, the additional OUT3 output can provide data such as dew point, absolute humidity, mixing ratio, or wet-bulb temperature. These values support a more precise assessment of condensation risks and moisture ingress.

This allows cooling, ventilation, and dehumidification to be based on reliable measurements—with the goal of maintaining stable storage conditions, avoiding unnecessary cycling, and ensuring the long-term quality of the stored fruit.

Choose the right humidity sensors for your fruit storage facility now

In fruit storage facilities with frequent temperature fluctuations, high humidity, and a risk of condensation, traditional humidity sensors quickly reach their limits—especially when stable, controllable measurement values are critical to storage quality. This is exactly where the AFTF-35 and KFTF-35 come in: They deliver reliable signals even under real-world, dynamic conditions and ensure dependable climate control.

Specifically, this means for you:

  • Stable readings even during humidity spikes and condensation
  • lower failure and maintenance rates
  • More precise control of cooling, ventilation, and dehumidification

Depending on the installation situation, choose the appropriate model: AFTF-35 for in-room installation or KFTF-35 for installation in ventilation ducts.

Here's how to ensure consistent storage conditions—and thus the quality, freshness, and cost-effectiveness of your stored fruit.

Discover sensors for high humidity in fruit storage facilities now

FAQ

Which humidity sensor is suitable for fruit storage?

Condensation-protected humidity and temperature sensors are suitable for fruit storage facilities with high humidity and an increased risk of condensation. They ensure stable readings during critical periods of high humidity and can be integrated into storage systems, building management systems (BMS), or distributed control systems (DCS).

Where should a humidity sensor be installed in a fruit storage facility?

The sensor should be mounted in a representative location with sufficient airflow. Avoid extreme local conditions such as areas directly near doors, immediate cold air currents, heat sources, or areas with poor airflow behind stacks of merchandise.

Why is the dew point important in fruit storage?

The dew point helps assess the risk of condensation. If the temperature drops below the dew point on cold surfaces, Humidity can condense—for example, on components, packaging, or sensor surfaces.