S401 – Thermal mass flow meter with insertion technology

Insertion thermal mass flow sensor, ideal for monitoring compressed air and process gases.

Insertion-type flow sensor, ideal for flexible installations and direct measurement under pressure.
Thermal mass flow measurement, independent of system pressure and temperature.
High accuracy and wide measuring range, suitable for detecting everything from large flow rates to small air or gas leaks.
Internal memory with two calibration curves, allowing the same sensor to be used with two different gases while maintaining maximum accuracy.
Integrated digital display for real-time visualization of instantaneous flow and totalized consumption.
Compatible with pipe diameters from 1” to 12” (other diameters available upon request).
Can be installed without shutting down the pressurized line (see installation video).
Robust housing with IP65 protection, designed for demanding industrial environments.
Isolated analog and pulse outputs, plus MODBUS / RTU interface for integration with monitoring systems.
Ultra-fast response time, ensuring stable readings even under fluctuating flow conditions.

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Description

Precise Control of Compressed Air and Industrial Gas Consumption – S401

Take full control of compressed air and industrial gas consumption in your plant.
The S 401 thermal mass flow sensor is designed for precise measurement of volumetric flow and total consumption of compressed air and non-corrosive gases in industrial systems, even under demanding operating conditions. Thanks to its wide measuring range, high resolution, and fast sampling rate, the S 401 delivers quick, stable, and highly accurate readings—ideal for consumption monitoring, leak detection, and energy optimization applications. Its insertion-type design allows flexible installation under pressure via a ball valve or G ½” process connection, without the need to shut down system operation. In addition, the sensor can store two calibration curves in its internal memory, enabling accurate measurement of two different gases without requiring additional recalibration. The optional color display, integrated directly into the sensor, enables real-time visualization of flow and consumption, as well as configuration of key parameters such as pipe diameter, gas type, measurement units, and output scaling. For easy integration into control and automation systems, the S 401 offers multiple signal output options, including: -4–20 mA analog output -Pulse output for consumption measurement -Modbus / RTU digital interface, allowing remote access to all measured values With its IP65 stainless steel housing, the S 401 is a robust, reliable, and precise solution for efficient compressed air management in industrial environments.

Applications

The S 401 flow sensor is designed for measuring and monitoring compressed air and industrial gas consumption across a wide range of in-plant applications. Thanks to its flexible configuration, it can be adapted to different processes and operating conditions.

Measurement of compressed air flow and consumption in industrial systems.

Monitoring of non-corrosive industrial gases such as oxygen, natural gas, CO₂, and other technical gases.

Energy consumption control and efficiency analysis in compressed air networks.

Leak detection and loss assessment in distribution lines.

Integration into industrial monitoring and automation systems via analog signals, pulse outputs, or digital communication.

Parameters such as gas type, measurement unit (volumetric or mass), and reference conditions (FAD or NORMAL) can be configured at the factory, via the optional display, or through the service kit.

The service kit includes PC software and a USB interface, enabling simple and secure configuration, adjustment, and diagnostics of the sensor.

Advantages

Wide measuring range, suitable for different flow velocities and pipe diameters.

Thermal mass flow measurement technology, largely independent of pressure and temperature variations.

High accuracy and excellent repeatability, ideal for consumption measurement and leak detection.

Very fast response time, even under dynamic flow changes.

Internal memory with two calibration curves, allowing accurate measurement of two different gases.

Multiple signal output options:

4–20 mA analog output

Pulse output for consumption measurement

Modbus / RTU interface for digital communication

Easy integration into energy management and industrial automation systems.

Videos

Measurement Principle and Long-Term Performance

The S 401 is designed to operate reliably in demanding industrial environments, combining mechanical robustness, measurement stability, and ease of maintenance. Its 316L stainless steel body and IP65 protection rating ensure safe operation even in areas with vibration, dust, or moderate humidity.

The glass-coated resistive sensor measurement principle provides high long-term stability, reducing drift and maintaining accuracy even in applications with thermal process variations. This makes it a suitable solution for continuous monitoring and long-term consumption analysis.

The insertion-type design simplifies not only initial installation but also inspection, cleaning, and maintenance tasks, without the need to dismantle the entire pipeline. In addition, when installed with a ball valve, the sensor can be removed under pressure, minimizing downtime and operational risks.

The recommended calibration interval is one year, helping to maintain measurement reliability in critical applications. Calibration is performed under controlled factory conditions and may be influenced by factors such as high humidity, the presence of oil, or particles in the system; therefore, use in well-filtered compressed air systems is recommended.

Thanks to its compatibility with different reference standards (ISO 1217 / DIN 1343) and the availability of multiple measurement units, the S 401 easily adapts to energy audits, internal reporting, and energy efficiency programs, both at local and corporate levels.