High-Temperature Temperature and Humidity Transmitter Explained: A Comprehensive Guide from Principle to Installation

In industrial production and extreme environment monitoring, high-temperature temperature and humidity transmitters play a critical role. They accurately capture temperature and humidity changes under high-temperature conditions, ensuring process stability and equipment safety. As a professional sensor brand, Nexisense is known for the durability and precision of its high-temperature series products, which are suitable for a wide range of harsh scenarios. This article systematically explores the definition, principles, structure, advantages, installation, and applications, providing practical guidance.

Definition of High-Temperature Temperature and Humidity Transmitters

A high-temperature temperature and humidity transmitter is an integrated instrument specifically designed for high-temperature environments. It simultaneously measures temperature and relative humidity and converts the data into standard output signals such as 4–20 mA, RS485, or 0–10 V. Unlike standard transmitters, its probes and materials are resistant to high temperatures, typically supporting operating ranges of 150°C or higher, and in some cases even more.

The Nexisense high-temperature series emphasizes integrated design and supports multi-parameter output, making it easy to connect to PLC or SCADA systems. In high-temperature gas, liquid, or solid media, it provides real-time data to support process optimization.

Working Principle of High-Temperature Temperature and Humidity Transmitters

High-temperature transmitters combine mature sensing technologies to ensure accuracy under extreme conditions.

Temperature measurement mainly uses resistance temperature detectors (RTDs) or thermocouples.

The PT100 RTD operates based on the linear relationship between platinum resistance and temperature: as temperature increases, resistance rises. This change is accurately converted through a Wheatstone bridge or constant current source.

Thermocouples (such as type K) generate a thermoelectric voltage based on the temperature difference between two dissimilar metal junctions. After reference junction compensation, the measured temperature is calculated, making them suitable for higher temperature ranges.

Humidity measurement typically adopts capacitive technology: a polymer film absorbs water molecules, changing its dielectric constant and causing corresponding capacitance variations. The circuit processes this signal to output humidity values.

Some models combine resistive or electrochemical methods to enhance adaptability in specific environments. Nexisense products incorporate compensation algorithms to reduce cross-interference between temperature and humidity measurements.

Structural Design of Nexisense High-Temperature Temperature and Humidity Transmitters

Nexisense high-temperature transmitters adopt a heat-resistant modular structure. The main components include:

High-temperature probe: protected by stainless steel or ceramic materials, integrating temperature and humidity sensing elements, with sintered filters for dust and corrosion protection.

Signal processing unit: includes amplifiers, A/D converters, and microprocessors for compensation and linearization.

Housing and interfaces: fully metal-sealed with IP67 protection, supporting flange, threaded, or insertion mounting.

The cable uses high-temperature-resistant silicone or armored designs. Some models feature isolation extension rods to prevent electronic components from direct exposure to high temperatures.

This design ensures probe resistance to temperatures above 300°C while keeping the main electronics within normal operating conditions.

Core Advantages of High-Temperature Temperature and Humidity Transmitters

In high-temperature environments, these transmitters demonstrate multiple advantages:

Wide temperature tolerance: probes support higher temperatures with minimal measurement drift.

High precision and stability: cross-compensation reduces errors, ensuring long-term reliability.

Strong interference resistance: shielding design protects against vibration, electromagnetic interference, and corrosion.

Flexible installation: multiple mounting options adapt to pipelines, wall mounting, or insertion.

Nexisense series transmitters feature low power consumption and support digital protocols, enabling remote monitoring and system integration.

Typical Application Scenarios

Industrial boilers and kilns: monitoring temperature and humidity in combustion chambers or flue gas to optimize combustion efficiency.

Heat treatment furnaces: controlling quenching or annealing atmospheres to ensure material properties.

Drying chambers and ovens: providing real-time humidity feedback to prevent over-drying or condensation.

Chemical reactors: monitoring under high-temperature and high-pressure conditions to ensure process safety.

Textile and food processing: improving product quality during high-temperature dyeing or drying processes.

Nexisense products perform reliably in these scenarios and can meet explosion-proof requirements.

Measurement Methods and Output Parameters

Temperature measurement commonly uses RTDs or thermocouples, while humidity measurement mainly relies on capacitive sensors.

Output options include analog signals such as 4–20 mA and digital RS485 (Modbus RTU), with some models supporting HART communication.

Multiple parameters are available, including temperature (°C), humidity (%RH), and even dew point calculations.

Installation Guide for High-Temperature Temperature and Humidity Transmitters

Installation directly affects measurement accuracy. Key steps include:

Selecting the location: ensure representativeness and avoid heat sources, dead zones, and interference.

Pipeline installation: insertion depth should be approximately one-third to one-half of the pipe diameter, using high-temperature-resistant sealing.

Wall mounting or insertion: ensure firm fixation and maintenance-friendly height.

Cabling: use heat-resistant cables and keep them away from high-temperature surfaces.

Inspect the device and prepare tools before installation; verify connections and functionality afterward.

Nexisense provides compatible accessories to simplify installation.

Maintenance and Care

Regularly clean the probe filter to prevent dust accumulation.

Calibrate every 6–12 months, adjusting the interval based on environmental conditions.

Inspect cables for aging and store the device in a dry environment during downtime.

These practices help extend service life and maintain measurement accuracy.

Typical Technical Specifications

Reference specifications for Nexisense series include:

Temperature range: -40°C to +200°C (or higher)

Humidity range: 0–100% RH

Accuracy: temperature ±0.5°C, humidity ±2% RH

Response time: temperature < 30 s, humidity < 10 s

Protection rating: IP67, optional pressure resistance

Power supply: DC 12–24 V

Model selection should consider maximum temperature and media corrosiveness.

How to Select and Use High-Temperature Temperature and Humidity Transmitters

Evaluate temperature limits, humidity range, and installation environment. Nexisense offers solutions from standard to customized models, and consultation is recommended to match specific requirements.

Frequently Asked Questions (FAQ)

Is humidity measurement accurate at high temperatures?

Yes. High-quality capacitive sensors with compensation algorithms minimize cross-effects and maintain accuracy.

Can the probe directly contact liquids?

Some insertion-type probes can, but the protection rating of the specific model must be confirmed.

How can signal interference be reduced?

Use shielded cables and keep them away from strong electromagnetic sources.

What is the typical service life?

With proper maintenance, service life is generally 5–10 years, depending on environmental conditions.

Do the devices support wireless communication?

Some Nexisense models support IoT expansion with wireless connectivity.

Conclusion

High-temperature temperature and humidity transmitters are core components of high-temperature process control, reflecting professional design from sensing principles to installation practices. Nexisense products provide practical solutions through reliability and ease of use. As industrial efficiency and safety become increasingly important, correct selection and installation of these devices can significantly enhance monitoring capability and production stability. Their contribution to a broader range of high-temperature applications is highly anticipated.