OVERVIEW
• Type J Thermocouple
• 12 mm & 14 mm ID
• -0°F to 400°F operating range (-18°C to 204°C)
• Bendable ring terminal
MADE IN THE USA
Our Cylinder Head Temperature (CHT) sensors are specifically designed for use in racing, tuning, and testing applications. Made in the USA from superior materials.
We use top quality, long-lasting, high temperature, waterproof potting compound at the probe/wire transition, which prevents moisture from entering into the transition causing shorts. Our wires are FEP insulated to protect from shorting and corrosion.
All of our CHT sensors are handmade in the USA
IMPORTANT NOTE: Please confirm with your instrument manufacturer that the instrument is compatible with a Type J thermocouple sensor.
Options:
TECHNICAL SPECIFICATIONS
Thermocouple type: | Type J |
Accuracy: | +/-0.4% of reading or about +/- 1.1°C (Special Limits of Error) |
Operating Temperature Range: | 0 °F to 400 °F (-18 °C to 204 °C) |
Response Time: | 1500 mS |
Available Inner Diameter Sizes: | 0.48 inches (12 mm) |
Cable: | Stainless steel over-braid cable with FEP insulated conductors, 6 feet or 12 feet |
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About - Type J CHT Ring Terminal Sensor — Cylinder Head Temperature
Why Type J for Cylinder Head Monitoring
Cylinder head temperature measurement requires matching the thermocouple type to the instrument input.
The CHT-WS Type J sensor uses an iron-constantan thermocouple, which produces a different voltage curve than Type K. If a sensor and instrument are mismatched, readings will be consistently incorrect.
Type J thermocouples also produce higher output voltage per degree in lower temperature ranges, which can improve sensitivity in cylinder head temperature applications.
Temperature Range
- -50°F to 400°F (-45°C to 204°C)
This range covers the typical operating conditions for air-cooled and small-engine cylinder head monitoring.
Ring Terminal Design
The ring terminal places the sensing junction inside a flat washer that installs under the spark plug.
When the plug is torqued:
- The ring is clamped against the cylinder head
- Heat transfers directly through the metal interface
- The sensor provides a representative measurement of head temperature
This design requires:
- No drilling
- No tapping
- No welding
The ring can be bent up to 90 degrees to allow proper wire routing.
Spark Plug Size Options
Available inner diameters:
- 10 mm
- 12 mm
- 14 mm
Selecting the correct size ensures proper clamping and accurate readings.
Response Time
- 1500 ms (time constant)
Response time is defined as the time required to reach 63.2% of a step temperature change.
This reflects the thermal mass of the ring design and is appropriate for the relatively gradual temperature changes in cylinder head applications.
Construction and Materials
- Thermocouple type: Type J
- Junction: Ungrounded
- Cable: Stainless steel overbraid with Teflon-insulated conductors, 20 AWG
- Ring thickness: ~0.040" (1.0 mm)
The overbraid provides abrasion resistance, while the insulation resists fuel, oil, and heat exposure.
Accuracy
- ±0.4% of reading or ±1.1°C (Special Limits of Error)
Wiring
Type J polarity must be maintained:
- White = Positive (+)
- Red = Negative (–)
Instrument Compatibility
Ensure your gauge or ECU is configured for Type J thermocouple input.
Using a Type K sensor with a Type J input (or vice versa) will produce incorrect readings.
Applications
- Air-cooled engines
- Karting and small engines
- Aviation (experimental only)
- Engine testing and development
Summary
The CHT-WS Type J ring terminal sensor provides a simple and reliable method for measuring cylinder head temperature.
- No machining required
- Direct spark plug installation
- Accurate and repeatable measurements
- Durable construction for demanding environments