SMBD-TC Surface Mount Bolt-Down CHT Sensor

Bolt-Down and Cement-On Attachment Options

The SMBD-TC is designed for applications where neither a spark plug installation nor a threaded boss is available. Instead of requiring a dedicated port, it uses a compact aluminum mounting fitting that can be secured directly to a surface using a #4 machine screw, or bonded in place using a high-temperature epoxy adhesive.

The bolt-down method provides a rigid, repeatable attachment that maintains consistent contact pressure through temperature cycling. This is especially useful in permanent or semi-permanent installations where measurement repeatability is important. The cement-on approach offers flexibility for curved or irregular surfaces where drilling is not practical, or where a temporary installation is preferred.

For adhesive mounting, a filled epoxy rated for at least 300°F continuous service should be used to prevent softening or sensor movement at operating temperature.

Mounting Versatility and Use Case

Unlike ring terminal sensors or threaded probes, the SMBD-TC can be placed directly onto flat or near-flat surfaces without modifying the component. This makes it particularly useful for:

• Cylinder head exterior surfaces 
• Exhaust manifold flanges 
• Intake manifold walls 
• Oil pans and housings 
• Brake components and mounting structures 

It is especially valuable in R&D and testing environments, where measurement points need to be added to existing designs that were not originally instrumented.

Materials and Construction

The mounting fitting is made from aluminum, which provides a balance of:

• Good thermal conductivity for efficient heat transfer  
• Low mass for faster response compared to heavier materials 
• Ease of machining for consistent surface contact 

While aluminum is not suited for highly corrosive chemical environments, it performs well in typical automotive and motorsports conditions including exposure to oil, fuel, coolant, and water.

The sensor is available with Type E, J, K, or T thermocouple calibrations, depending on system requirements. 

Junction configurations include both grounded and ungrounded options.

Temperature Range and Performance

• Temperature range: -50°F to 500°F (-45°C to 260°C) 
• Accuracy: ±0.4% of reading or ±1.1°C (Special Limits of Error) 

This range is well suited for surface temperature measurement of engine and mechanical components operating below exhaust gas temperatures.

Response Time

• Response time: approximately 6 seconds (time constant) 

Response time is defined as the time required to reach 63.2% of a step temperature change. As a surface-mounted sensor, response is influenced by both the sensor construction and the thermal mass of the measured component.

Lead Wire and Cable Construction

The sensor includes:

• FEP (Teflon™) insulated lead wire 
• 30 AWG solid conductors 
• Insulation rated to 400°F (204°C) 

The cable is suitable for typical engine bay environments and can be extended using matching thermocouple extension wire.

Connector options include:

• No connector 
• Mini thermocouple plug 
• Standard thermocouple plug 

Mounting Details

• Mounting hole sized for #4 screw (0.113" diameter) 
• Flat mounting surface recommended for best thermal contact 
• Consistent contact pressure improves measurement repeatability 

Environmental Rating

• IP64 rating 

Provides protection against dust ingress and splashing water, suitable for most test and industrial environments.

Applications

• Engine development and testing 
• Cylinder head surface monitoring 
• Intake and exhaust component evaluation 
• Oil system temperature measurement 
• Brake and structural component testing 

Summary

The SMBD-TC surface mount thermocouple provides a flexible and practical solution for measuring temperature on components that cannot accept traditional probe installations.

• Bolt-down or adhesive mounting options 
• Multiple thermocouple types available 
• Durable, lightweight construction 
• Ideal for R&D and retrofit instrumentation