Product Overview

The thermal flow switch NK300A  (also including the NK300B model ) is a high-performance flow monitoring device based on thermal principles. It is a dual-use sensor designed for gas, hydraulic oil, water, and cutting fluids. Its design with no moving parts ensures maintenance-free operation and long-term safety.

Technical Specifications Table

• Setting range: 1… 150 cm/s (water), 3… 300 cm/s (oil)
• 20… 2000 cm/s (air)
• Signal output: PNP, NPN, relay
• Normally open+normally closed (SPDT)
• Power supply: 24V ± 20% DC or 230V ± 15% AC
• Connecting current: maximum 400mA (PNP or NPN type)
• NK300 maximum 4A (relay type); NK600 type maximum 1A@48ac /dc
• No load current: maximum 80mA
• Flow indicator: LED row (6 pieces)
• Setting method: Potentiometer setting
• Pressure resistance range: 100bar
• Temperature gradient: 4 ℃/S
• Response time: 1-13S, typical value of 2S
• Initialization time: 8S
• Electrical protection: reverse phase, short circuit, overload protection
• Protection level: IP67
• Medium temperature: -20-100 ℃
• Environmental temperature: -20-80 ℃
• Storage temperature: -20-100 ℃
• Wiring method: M12 connector/directly attached 2-wire optional
• Material: Probe: Stainless Steel
• Shell: Stainless steel PBT
• Weight: 0.4Kg
• Repeatability accuracy: ± 2% of measured values
• Note:
  For specific installation and usage, please refer to the above parameters. If you have any questions, please contact our company in a timely manner.
  If any problems are found during use, please contact the supplier in a timely manner. It cannot be easily disassembled. If such a situation occurs, our company will not be responsible and reserves the right to pursue legal action
  Corresponding legal responsibilities.

Key Functions and Features

1. Thermal Dispersion Measurement

The NK300A utilizes two resistors within a closed probe: a detection resistor (heated) and a reference resistor (unheated). As the mass flows, heat is carried away from the heated resistor, and the change in resistance difference is used to determine the flow rate.

2. Intelligent Interface

• LED Indicators: Features a 6-piece LED display for flow trends and switch status.

• Adjustable Settings: The switch quantity is continuously adjustable via a potentiometer.

• Physical Advantages: Compact structure with extremely low pressure loss and easy installation for various pipe requirements.

Industrial Applications

The dual-use capability makes the NK300A ideal for:

• Pneumatic and Hydraulic Systems: Monitoring fluid cycles.

• Circulating Water Monitoring: Ensuring proper flow for cooling systems.

• Machinery Protection: Monitoring cutting fluids and lubricating oils.

• Pump Idle Protection: Preventing pump damage from dry running.

Size chart

Frequently Asked Questions (FAQ)

Does the NK300A require regular maintenance?

No. The NK300A uses thermal dispersion technology with no moving mechanical parts, allowing maintenance-free operation under normal working conditions.

What media can the NK300A monitor?

The sensor is designed for water, hydraulic oil, cutting fluids, lubricating oil, and air within the specified operating parameters.

What is the maximum operating pressure?

The maximum pressure rating is 100 bar.

Which output signals are available?

The NK300A supports:

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

What wiring options are available?

The sensor supports:

• M12 connector
• Optional direct-attached cable

Can the switching point be adjusted?

Yes. The switching point can be continuously adjusted using the built-in potentiometer.

Typical Application Example

In industrial cooling water circulation systems, maintaining continuous flow is essential to protect pumps and heat exchangers. The NK300A thermal flow switch can monitor the flow condition in real time and output a switching signal when flow falls below the preset value. Because the sensor has no moving parts, it is suitable for long-term operation in circulating water, lubrication, or cutting fluid systems where reduced maintenance is desired.

Why Choose the Thermal Flow Switch NK300A ?

The NK300A Series is suitable for industrial users who require stable flow monitoring with minimal maintenance.

Key advantages include:

• Thermal dispersion measurement with no moving parts
• Suitable for both liquids and gases
• Maintenance-free operation
• Low pressure loss
• Compact structure for easy installation
• Multiple output options (PNP, NPN, Relay)
• LED flow status indication
• High protection rating (IP67)
• Supports M12 connector or direct cable connection