Thermal Flow Switch NK300B

Product Overview

The Thermal Flow Switch NK300B is an intelligent electronic flow monitoring device based on the thermal dispersion principle. It is designed for reliable flow detection in both liquid and gas applications.

The sensor contains two precision resistors inside a sealed probe. One resistor is continuously heated and functions as the sensing element, while the other serves as a temperature reference. By monitoring the temperature difference between the two resistors, the flow switch accurately detects changes in flow velocity.

With no moving mechanical parts, the Thermal Flow Switch offers high reliability, excellent repeatability, and minimal maintenance, making it ideal for modern industrial automation systems.

---

Operating Principle

The Thermal Flow Switch operates based on the thermal dispersion principle.

Inside the sealed probe are two resistors:

• One heated resistor acts as the sensing element.
• One unheated resistor serves as the reference element.

When the process medium flows past the probe, heat is carried away from the heated resistor. This changes its resistance value. The controller continuously compares the difference between the heated resistor and the reference resistor to determine whether the flow rate exceeds or falls below the preset switching point.

This measuring principle enables accurate flow monitoring without moving mechanical components.

---

Product Applications

The Thermal Flow Switch NK300B is suitable for both liquid and gas media and is widely used in industrial automation and fluid monitoring applications, including:

• Pneumatic systems
• Hydraulic systems
• Circulating water monitoring
• Cutting fluid monitoring
• Lubricating oil monitoring
• Pump dry-run protection
• Cooling systems
• Industrial machinery
• Process automation

---

Product Features

• Thermal dispersion measurement principle
• Suitable for both liquid and gas media
• No moving mechanical parts
• High measurement reliability
• Fast response and excellent repeatability
• LED flow status indication
• Adjustable switching point via potentiometer
• Multiple output options:
  • PNP
  • NPN
  • Relay
  • SPDT (Normally Open + Normally Closed)
• Reverse polarity, short-circuit, and overload protection
• Compact and durable industrial design
• IP67 protection rating
• Supports M12 connector or direct cable connection
• Optional customized 4-wire wiring configuration

---

Technical Specifications

Flow Setting Range

---

Signal Output

---

Power Supply

---

Switching Capacity

---

Electrical Specifications

---

Electrical Protection

• Reverse polarity protection
• Short-circuit protection
• Overload protection

---

Environmental Specifications

---

Electrical Connection

---

Materials

---

Weight

---

Wiring

The standard wiring method is provided with an M12 connector or direct cable connection.

A customized 4-wire wiring configuration is also available to meet specific application requirements.

Size chart（mm）

---

Typical Applications

The Thermal Flow Switch is suitable for a wide range of industrial applications, including:

• Industrial automation
• Hydraulic systems
• Pneumatic systems
• Cooling water systems
• Lubrication systems
• Machine tool coolant monitoring
• Pump protection
• HVAC systems
• Water treatment equipment
• OEM machinery

---

Product Advantages

The Thermal Flow Switch NK300B combines thermal dispersion sensing technology, high reliability, and multiple output options in a compact industrial design. Its non-mechanical measuring principle eliminates wear caused by moving parts while providing stable flow monitoring for liquids and gases. With IP67 protection, LED flow indication, and comprehensive electrical protection, it is well suited for demanding industrial environments.

---

Frequently Asked Questions (FAQ)

How does the Thermal Flow Switch NK300B work?

The Thermal Flow Switch uses the thermal dispersion principle. A heated resistor and a reference resistor inside the probe detect changes in heat transfer caused by fluid flow, allowing the device to monitor flow conditions accurately.

What media can the Thermal Flow Switch NK300B monitor?

It is suitable for both liquids and gases, including water, lubricating oil, cutting fluids, compressed air, and other compatible media.

What output options are available?

The switch supports:

• PNP
• NPN
• Relay
• SPDT (Normally Open + Normally Closed)

Does the flow switch provide visual status indication?

Yes. The device features a 6-LED flow indicator that displays the current flow condition for easy on-site monitoring.

What protection rating does the product provide?

The Thermal Flow Switch is rated IP67, providing excellent protection against dust and water ingress for industrial environments.

Why Choose the Thermal Flow Switch NK300B?

The Thermal Flow Switch NK300B provides precise and reliable flow monitoring for both liquid and gas applications. With its thermal dispersion sensing technology, multiple output configurations, IP67 protection, and LED flow indication, it is an excellent solution for industrial automation, hydraulic systems, pneumatic systems, cooling circuits, and pump protection applications where stable and maintenance-free flow detection is required.