Adjustable Bayonet Thermocouple Type J (Spring Loaded)
The Hongtai Adjustable Bayonet Thermocouple is the universal “One-Size-Fits-All” temperature sensor for the plastics and packaging industries. Designed specifically as an Injection molding temperature sensor, it features a distinctive spring-loaded cap that locks onto a bayonet adapter (sold separately).
The key advantage is the Adjustable spring loaded thermocouple mechanism. The bayonet cap can be twisted up or down the spring (approx 200mm adjustment range). This allows a single sensor to fit into mounting holes of various depths, reducing your spare parts inventory. The spring tension ensures the probe tip is pressed firmly against the bottom of the hole, eliminating “air gaps” and ensuring accurate reading of the barrel or nozzle temperature.
Key Technical Features & Benefits
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Universal Fit: The flexible spring allows you to adjust the immersion length on-site. One 2-meter sensor can replace dozens of fixed-length probes.
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Positive Contact: The compressed spring forces the tip against the metal, eliminating thermal resistance. Critical for reliable Extruder thermocouple control.
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Tool-Free Installation: Twist-lock bayonet cap installs in seconds without wrenches.
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Durability: Stainless steel braided lead wire protects against abrasion from moving mold platens and hot plastic drool.
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Fast Response: Standard grounded junction delivers instant feedback to the PID controller.
Technical Specifications (WRN-291 Series)
| Parameter | Specification | Notes |
| Product Type | Bayonet thermocouple type J | Also available in Type K |
| Temp Range | 0°C to 400°C (Standard) | Up to 600°C (High Temp) |
| Probe Diameter | 4.8mm (3/16″), 6.0mm, 8.0mm | 4.8mm is most common |
| Bayonet Cap Size | 12mm ID (Fits 12mm Adapter) | 15mm ID (Large Cap) |
| Lead Wire | 1m, 2m, 3m, 5m | Stainless Steel Braid |
| Adjustment Range | Up to 200mm along the spring | – |
| Tip Shape | Round, Flat, or Pointed | Round is Standard |
| Adapter Type | 1/8″ NPT, 1/4″ NPT, M10, M12 | Sold Separately |
Industry Applications
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Injection Molding: Heating barrel zones and nozzle bodies.
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Extruders: Barrel heating for pipe and profile extrusion.
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Packaging Machinery: Sealing bars and heat tunnels.
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Rubber Vulcanizing: Mold platen temperature control.
How to Adjust the Bayonet Cap
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Insert: Place the probe tip into the hole until it bottoms out.
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Compress: Push the spring down until it feels firm.
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Lock: Hold the spring in position and twist the Bayonet Cap onto the spring coils.
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Install: Hook the cap onto the mating adapter pins. The spring should be compressed about 10-15mm to maintain positive pressure.
FAQ
Q: Do I need Type J or Type K?
A: Bayonet thermocouple type J (Iron-Constantan) is the standard for US/European plastics machinery because it offers higher sensitivity in the 200-400°C range. Type K is more common in Asian machinery. Check your controller setting or plug color (Black=J, Yellow=K).
Q: Does the sensor include the thread adapter?
A: Typically, the sensor includes the Probe, Spring, and Cap. The Bayonet Adapter (the part that screws into the machine) is reusable and usually stays on the machine. If you need new adapters (M12 or 1/4″ Thread), please specify “With Adapters” on your order.
Q: Why is my reading fluctuating?
A: This is usually due to poor contact. Ensure the Adjustable spring loaded thermocouple has enough tension. If the spring is loose, the tip will “float” in the hole, reading air temperature instead of metal temperature.
(Pair with our Cartridge Heaters for a complete injection molding heating.
