1. Product Overview
The Turck NK300A Thermal Conductivity Electronic Flow Switch is a versatile sensor designed for reliable flow monitoring in various applications. Utilizing a thermal principle, it detects flow velocity by measuring heat dissipation from a heated resistor. This device is suitable for both gas and liquid media, offering maintenance-free operation and easy installation.
Key Features:
- No moving parts, ensuring high reliability and minimal maintenance.
- Easy installation with a compact structure.
- One model adaptable to various pipe diameter requirements.
- Continuously adjustable switching value.
- Extremely low pressure loss.
- LED display for real-time flow trend and switch status.
- Suitable for pneumatic and hydraulic systems.
- Ideal for flow monitoring of circulating water, cutting fluid, and lubricating oil.
- Provides dry-running protection for pumps.
2. Specifications
The NK300A flow switch offers robust performance for industrial applications.
| Parameter | Value |
|---|---|
| Model | NK300A |
| Setting Range (Water) | 1...150 cm/s |
| Setting Range (Oil) | 3...300 cm/s |
| Setting Range (Air) | 20...2000 cm/s |
| Output Type | PNP, NPN, Relay, Analog (4...20mA) |
| Power Supply | 24V ±20% DC (max 80mA for PNP/NPN, max 4A for Relay), 24VDC or 1A, 230VAC |
| No-load Current | Max 80mA |
| Flow Indication | 6 LEDs |
| Setting Method | Potentiometer setting |
| Pressure Resistance | 100 bar |
| Medium Temperature Change | ≤4°C/s |
| Response Time | 1...13s (Typical 2s) |
| Initialization Time | Approx. 8s |
| Electrical Protection | Reverse polarity, short circuit, overload protection |
| Protection Class | IP67 |
| Medium Temperature | -20...90°C |
| Ambient Temperature | -20...80°C |
| Storage Temperature | -20...100°C |
| Wiring Method | M12 connector / 2m cable directly attached |
| Material (Probe) | Stainless Steel |
| Material (Housing) | PBT |
| Weight | 0.4 kg |
3. Setup and Installation
Proper installation is crucial for the accurate and reliable operation of the NK300A flow switch. The sensor is an insert-type and requires a welded sleeve or tee joint for installation.
General Installation Guidelines:
- Pipe Straight Section: When installing near bends or intersections, ensure the straight pipe distance from these points is at least 4 times the pipe diameter (a ≥ 4d). This helps ensure stable flow conditions for accurate measurement.
- Partially Filled Pipes: If the medium does not completely fill the pipe, the sensor should be installed at the bottom of the pipe to ensure the probe is fully immersed in the medium.
- Sediment Presence: If sediment may be present in the pipe, install the sensor horizontally on the side. Ensure there is no air near the probe to prevent false readings.
- Low Thermal Conductivity Media: For media with low thermal conductivity (e.g., certain oils and high-fat liquids) or when rapid temperature changes are expected, consider the sensor's position relative to the fluid direction. The probe's orientation should be perpendicular to the fluid flow direction.
Wiring Diagrams:
The NK300A supports various output types. Refer to the following diagrams for correct wiring:
- PNP Output: Connect L+ to pin 1, White wire to pin 2, Black wire to pin 4, Blue wire to pin 3, and L- to pin 3.
- NPN Output: Connect L+ to pin 1, White wire to pin 2, Black wire to pin 4, Blue wire to pin 3, and L- to pin 3.
- RELAY Output: Connect to pins 1, 5 (NO), 4 (COM), 2 (NC), and 3.
- 4...20mA Output: Connect L+ to pin 1, Black wire to pin 4, Blue wire to pin 3, and L- to pin 3.
4. Operating Instructions
The NK300A flow switch provides visual feedback through its LED indicators and allows for easy adjustment of set points.
LED Indicators:
- Switch Output Type:
- 4 Green LEDs: Indicate the degree to which the flow rate exceeds the set point (1, 2, 3, or 4 LEDs lit).
- 1 Yellow LED: Illuminates when the flow rate equals or exceeds the set point.
- 1 Red LED: Illuminates when the flow rate is below the set point.
- Analog Output Type:
- LEDs correspond to current output levels: 20 mA, >16 mA, >12 mA, >8 mA, >4 mA, 4 mA.
Setting the Flow Switch:
The flow switch features a potentiometer for adjusting the switch point or measurement range. This potentiometer is located under a dustproof screw at the front of the sensor to protect it from dust intrusion.
- For Switch Output Type: Use the potentiometer to adjust the desired flow switch point.
- For Analog Output Type: Use the potentiometer to adjust the measurement flow range.
Product Introduction Video:
Watch this video for a brief introduction to the product and its features.
5. Maintenance
The NK300A flow switch is designed for maintenance-free operation due to its lack of moving parts. However, regular checks can ensure its longevity and optimal performance.
- Regular Cleaning: Periodically inspect the sensor probe for any buildup of debris, scale, or other contaminants that might affect its accuracy. Clean gently if necessary, following appropriate safety procedures for your specific medium.
- Wiring Integrity: Ensure all wiring connections remain secure and free from corrosion or damage.
- Environmental Conditions: Verify that the ambient and medium temperatures remain within the specified operating ranges (-20 to 80°C ambient, -20 to 90°C medium).
- Physical Inspection: Check the sensor housing and probe for any signs of physical damage.
6. Troubleshooting
If you encounter issues with your NK300A flow switch, consider the following common troubleshooting steps:
- No Flow Indication / Incorrect Reading:
- Check power supply connections and ensure the sensor is receiving the correct voltage (24V DC).
- Verify that the sensor probe is fully immersed in the medium and that there are no air pockets, especially in pipes with potential sediment.
- Inspect the probe for any fouling or damage that might impede accurate detection.
- Ensure the installation location adheres to the recommended straight pipe distances from bends or intersections.
- Confirm the potentiometer setting is appropriate for the desired flow rate or measurement range.
- LEDs Not Illuminating:
- Check the power supply.
- Verify wiring connections according to the provided diagrams.
- Ensure the flow rate is within the detectable range and that the sensor is functioning correctly.
- Intermittent Readings:
- Check for unstable power supply.
- Inspect for loose wiring connections.
- Ensure the medium flow is stable and not subject to rapid fluctuations outside the sensor's response time.
- Electrical Protection Triggered:
- If reverse polarity, short circuit, or overload protection is activated, immediately disconnect power and inspect wiring for faults. Correct any issues before reapplying power.
For persistent issues, contact technical support.
7. User Tips
- Optimal Placement: For best accuracy, install the sensor in a section of pipe where flow is laminar and consistent, away from pumps, valves, or sharp bends.
- Calibration Check: Although factory calibrated, periodically verify the sensor's readings against a known flow rate if high precision is critical for your application.
- Environmental Awareness: Be mindful of the operating temperature limits for both the medium and the ambient environment to prevent damage and ensure reliable performance.
8. Warranty and Support
This product is typically covered by a standard technical warranty for one year. For specific warranty details, technical assistance, or if you have questions regarding the product's application or performance, please contact the seller or manufacturer directly. Ensure you have your product model number (NK300A) and any relevant purchase information available when seeking support.
