Refrigeration Industry – Reefer & Cold-Chain Sensors
Kjaerulf Pedersen a/s provides advanced sensor technology for the refrigeration industry. With extensive experience in reefer containers (refrigerated intermodal containers), we deliver solutions that ensure reliable temperature and humidity monitoring, pulp temperature measurement for cold treatment, and atmosphere management with CO₂ and O₂ sensors for both Controlled Atmosphere (CA) and Modified Atmosphere (MA) transport. Our sensors are designed for seamless RS485/Modbus integration across refrigeration applications including containers, truck & trailer units, cold stores and retail cooling.
Reefers (Refrigerated Intermodal Containers)
A reefer — also called a refrigerated intermodal container — is essential for transporting temperature-sensitive cargo across sea, rail and road. All reefers rely on accurate temperature sensing, and most on humidity as well, while Controlled Atmosphere (CA) and Modified Atmosphere (MA) containers add CO₂ and O₂ monitoring to optimize cargo quality and shelf life. Kjaerulf Pedersen a/s delivers proven sensor solutions for reefer applications, designed for RS485/Modbus integration, long-term durability and reliable operation in demanding environments.
Other Refrigeration Applications
Our sensor technology also applies in truck & trailer units, cold stores, retail counters, and cooling compressors.
Truck & Trailer Refrigeration
Temperature sensing for transport refrigeration units on the road.
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Cold Stores & Warehouses
Stable, documented storage temperatures from dock to rack.
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Counters, Shelves & Islands
Temperature monitoring for retail cooling displays.
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Cooling Compressors
Temperature and vibration monitoring for the heart of the cooling system.
View products →Sensors for Reefer Containers (Featured Products)
Humidity Sensor
Monitors relative humidity in reefer containers, enabling control systems to maintain optimal moisture levels and protect cargo quality during cold-chain transport.
Capacitive element · PTFE filter · no recalibration View product →
USDA Sensor
Insertion probe that reads pulp temperature inside perishable cargo — the reading cold treatment is documented on in reefer containers.
NTC insertion probe · 2.5 mm stainless tip · 15 m PUR View product →
CO₂ Sensor
Monitors CO₂ levels in CA/MA reefers, delivering the reading the container's atmosphere control regulates on.
Dual-wavelength NDIR · 0–20% CO₂ · IP67 View product →
O₂ Sensor
Measures oxygen in CA/MA reefers using Luminescence Quenching (LQ) — optical measurement with low drift and little service.
Luminescence Quenching · 0–25% O₂ · low drift View product →
Hybrid Sensor
Measures CO₂, O₂ and relative humidity in one housing, with a single mounting point and one Modbus address in the reefer container.
CO₂, O₂ & RH · single Deutsch plug · Modbus RTU View product →Integration & Durability
Kjaerulf Pedersen a/s sensors are designed for easy integration into reefer container control systems and long-term durability in demanding environments:
Frequently Asked Questions – Reefer Sensors
What is a reefer in shipping?
A reefer is a refrigerated intermodal container used to transport temperature-sensitive cargo across sea, rail, and road.
Do all reefers use CO₂ and O₂ sensors?
No. Standard reefer containers are equipped with temperature (and often humidity) sensors. CO₂ and O₂ sensors are only used in Controlled Atmosphere (CA) or Modified Atmosphere (MA) reefers, where the internal gas mix is actively managed.
How are sensors integrated into reefer systems?
Kjaerulf Pedersen a/s sensors use RS485 / Modbus RTU, ensuring seamless integration with reefer unit control systems for real-time monitoring.
What are the benefits of LQ O₂ sensing?
Luminescence Quenching (LQ) sensors measure oxygen optically instead of using a heated zirconia cell. In reefer containers this means lower power consumption, stable readings with minimal drift, and reduced maintenance or recalibration — ensuring reliable atmosphere control during long voyages and fleet operation.
When is multipoint temperature monitoring useful in reefers?
Multipoint monitoring is used to capture temperature variations in different parts of the container. A digital module like TempMux-8 reduces wiring, simplifies installation, and provides status and averaging for more reliable control and diagnostics.
What is the difference between Controlled Atmosphere (CA) and Modified Atmosphere (MA) in reefers?
Modified Atmosphere (MA) is a one-time gas adjustment at loading, typically reducing oxygen and adding CO₂ or nitrogen. The atmosphere is not actively controlled afterwards, making MA suitable for short to medium voyages. Controlled Atmosphere (CA) continuously monitors and regulates oxygen, CO₂, humidity, and sometimes ethylene levels throughout the voyage. CA maintains a stable atmosphere over long intercontinental shipments and significantly extends cargo shelf life.
What is a USDA sensor?
A USDA sensor, also called a USDA probe, is an insertion probe placed in the pulp of perishable cargo. It is used for cold treatment, where the temperature must be documented inside the produce and not only in the container air. The name describes that application, not a product certification.
How many USDA probes are used in a container?
A cold treatment enclosure other than a vessel hold requires at least three temperature probes. A vessel hold requires four.
Talk to Us About Refrigeration & Reefer Sensors
Kjaerulf Pedersen a/s delivers sensor solutions for the refrigeration industry — from refrigerated containers (reefers) to truck & trailer units, cold stores, retail counters and industrial cooling. Our portfolio covers temperature, humidity, CO₂, O₂ and multipoint monitoring, designed for reliable integration and long-term performance.