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RF/Microwave Heating – Fiber Optic Temperature Solutions

posted by Rugged Monitoring on 2020-07-06

Most times, the term “Microwave heating” is used to paint the picture of a kitchen with frozen or packaged food, and a microwave oven to heat the food before consumption. Though household microwave tempering is important, we will not be dwelling on it as the focus will be on fiber optic temperature solutions for Microwave heating at an industrial/commercial level.

What and Why of Microwave heating?

The electromagnetic radiation with frequencies between 300MHz to 300 GHz are considered as microwaves. Microwaves have multiple uses in communication, navigation, and spectroscopy. These microwaves can also be used in generating heat by rotating certain molecules into a liquid mixture. When the microwaves go through any mixture, they agitate the water molecules and charged ions. The agitation results into continuous rotation and rubbing and which in turn generates heat into the mixture. This phenomenon is called conversion of electromagnetic energy to thermal energy.

Many industries like textile, rubber, polymer, plastic, ceramic, glass, food processing, pharmaceutical etc. make use of microwave heating systems for faster heating with better quality. The direct penetration of microwaves into heating materials enables full volume heating in a fast and effective manner compared to conventional surface heating methods. Microwave heating are also energy efficient as they could save up to 95% of energy for a similar level of heating by conventional methods. The final product quality directly depends on the quality of the heating (Conventional / Microwave). Therefore, it becomes very important to control the heating in any application.

Fast and effective temperature control of heating process is another big advantage of microwave heating. The heating rate can easily be controlled by using a temperature sensor and adjusting the microwave power based on temperature threshold. Fast responsive and accurate temperature sensor is essential for effective microwave heating control. Most importantly, the temperature sensor must be safe and not create spark / arcing inside microwave.

Why choose Fiber Optic Temperature Sensors for Microwave Heating?

Fiber optic temperature sensors are one of the best alternate for accurate temperature monitoring of heating samples under microwave. The sensors can safely be placed directly on the heating sample and provide direct temperature measurement. The sensors, unlike thermocouples, do not need isolation as they are immune to electromagnetic interferences. Being in direct contact of heating samples, fiber optic temperature sensors provide more accurate temperature measurement compared to IR (Infrared) thermometers.

Therefore, microwaves fitted with fiber optic temperature sensors and a feedback temperature controller helps in maintaining the uniform heating. The Gallium Arsenide (GaAs) based fiber optic temperature sensors have proved to be the most robust, accurate and fast sensors for microwave heating applications. Theses sensors are easy to install and have a longer life span for industrial microwave heating applications. Furthermore, these sensors are bio-safe and do not contaminate heating samples. 

There are numerous applications in microwave heating that require effective temperature control with rugged and fast responsive temperature sensors.

Applications of Fiber Optic Temperature Sensors in Microwave Heating

GaAs based fiber optic temperature sensors are being used in many microwave heating applications in various industries. The most popular applications are listed below: 

1. RF/Microwave Assisted Drying

Fiber optic temperature sensors are used in effective temperature control in various industrial drying applications such as: Crop Fodder Drying, Crisp Drying, Fruit / Vegetable Drying, Post baking Dryers, Cannabis Drying, Flower Drying, Fiber Glass Yarn Drying, Hydrophilic Foam Drying, Ceramic Drying, Textile-Fabric/Yarn Drying, Wood Drying and Pest Control etc.

2. Microwave Assisted Digestion

Temperature control is very important in creating correct samples during microwave digestion. The fast-responsive fiber optic temperature sensors are being used for temperature control in various microwave digestion applications.

  • Pharmaceutical Drug Testing: ICP-MS Analysis
  • Clinical:  Biomedical samples Testing (urine, serum, whole blood, and hair)
  • Trace metal analysis in food and beverages including cooking oil
  • Analysis of soil contamination for toxic elements
  • Assessment of Sewage Sludge (DIN EN 13346, EPA 3051A)
  • QA/QC and contamination identification on metals, alloys, and ceramic
  • Trace metal analysis in cosmetics, cleaning agents, & Personal Care Products
  • Crude Oil, Petroleum products & Secondary Recovered Fuel Testing Determination of hazardous metals into Polymers and Plastics
  • Elemental analysis of Ocean bed polymetallic nodules or manganese nodules
  • Identification of heavy metal in Cannabis-based drug and products

3. RF/Microwave Assisted Thermal Sterilization

RF / microwave heating is widely used for pasteurization and sterilization of food, fodder, vegetables, wood, and cannabis. Temperature control using fiber optic temperature sensors is crucial for effective sterilization without impacting the quality of final product.

4. Microwave Assisted Extraction

The following applications of microwave extraction use fiber optic sensing based temperature controlling: 

  • Plant oil extraction e.g. Tea leaves, Cannabis etc.
  • Extraction of the essential oils of peppermint and rosemary from hexane and ethanol mixtures; Faster extraction of plant phenolic compounds
  • Microwave preconditioning of sugar cane prior to juice diffusion
  • Pyrolysis and Bio-Fuel Extraction
  • Herbal Drug Research
  • Pesticide analysis in Soil

5. Microwave Assisted Synthesis

Fiber optic temperature sensors are used in effective temperature control in various synthesis applications such as: Polymer Synthesis, Material Chemistry, Catalyst Preparations, Waste Management etc.

6. Radio Frequency (RF) heating for Soil Remediation

RF heating is used in decontaminating and restoring soil to its natural state. The RF heating is controlled using rugged and accurate fiber optic temperature sensors. 

7. RF heating for Oil Extraction

RF heating for oil extraction eliminates the need for using steam water. Temperature monitoring during the RF oil extraction is necessary in increasing the effectiveness.

8. Food Processing and Packaging

Microwave heating plays a significant role in food processing and packaging industry. Temperature controlled microwave heating helps in improving the quality of the food processing and packaging.


Gallium Arsenide fiber optic sensor is a rugged design manufactured to effectively function with microwave heating harsh environment. It has been tested and proven to a practical technology for monitoring temperature. The sensors are immune to high radio frequency and microwave fields to provide the best results for industry users.

We at Rugged monitoring are tirelessly working toward the continuous improvement of our fiber optic technology to ensure its availability, affordability, and sustainability in the market. 

For more inquiries, visit www.ruggedmonitoring.com.