The transportation industry requires precision sensors that can be used in tight control loops to accurately adjust throttle and braking controls as well as to monitor thermal conditions and other such quantities in motion. Smith Systems, Inc. serves these industries by providing rugged speed and temperature sensors, instrumentation, wiring harnesses, controls and all other components required to ensure the passenger safety. Whether moving by rail, road, air, sea or space, Smith Systems, Inc. develops cost-effective control solutions for these vehicles.

Smith Systems, Inc. believes in offering custom solutions designed around the customer’s needs, then sourcing components and construction at their North Carolina facility. High quality, reliable sensors that can withstand the harsh environments of the transportation industry do not require long lead times or high costs, but instead require the intense quality assurance and precision manufacturing methods employed by Smith Systems, Inc.

Markets served by Smith Systems, Inc.

Smith Systems, Inc. can provide sensors for both the original equipment manufacturer (OEM) specifications, as well as develop aftermarket sensors that improve upon existing designs.

These sensors have been used in both civilian and military vehicles, ranging from mining machines to railroad cars to spacecraft. They have built traction motors for mining equipment, speed sensors for NHRA and Indy car racing, railroad speed and anti-skid sensors, propeller speed control for all sizes of marine transportation and many other applications.


Today’s modern railways require accurate speed measurements and precision traction control to keep trains on the rails. Smith Systems, Inc. offers both active and passive sensors for determining wheel speed, which can then be used in a feedback loop to provide power to each traction motor as needed. The positive train control (PTC) produces several outputs, which can determine the speed and direction of a rotating target, such as a wheel or axle. These sensors are vibration and moisture resistant, and are flexible with added strain relief, making them rugged enough for railroad use in any climate. They hold several sensor patents with more pending.


Smith Systems, Inc. manufactures low-cost, high-volume speed sensors for the automotive manufacturing industry. Some are made from a molded polymer designed to withstand the high temperatures associated with internal combustion engines, including race engines on cars and motorcycles. Others are stainless steel, aluminum or cast housings. These sensors also resist moisture and volume and can be fitted with a number of standard vibration-proof connectors.


The output shaft speed for large ships and small personal watercraft must be known. Conventional speed sensors fail from corrosion due to salt spray and immersion in salt water, growth of biofilms and so on. Smith Systems, Inc. has developed specialized sensors for use in marine environments, improving the performance and reducing the maintenance costs of operating sea vessels.

Aviation and aerospace

The temperature from entrance to exhaust in turbine engines can be used to optimize efficiency and performance. Temperature sensors used for this purpose must be able to withstand extremely high temperatures and resist dust and corrosion, as conditions change rapidly in turbines. Smith Systems, Inc. designs sensors for these applications and is also an approved supplier to a primary systems contractor for the space shuttle program.

Products offered by Smith Systems, Inc.

It’s clear Smith Systems, Inc. serves virtually any transportation industry, meeting demands of these different markets by manufacturing a wide assortment of sensors. They offer speed sensors, temperature sensors and proximity sensors, all of which are vital to running safe means of transportation. They also offer control systems and cabling solutions in-house.

Speed sensors

Monitoring the speed of a rotating shaft, wheel or gear is essential to understanding how a vehicle is performing. It can tell the operator the traveling speed, RPM on a crankshaft, determine proper gear selection and so on. Speed data from multiple sources can be used as redundancy; individual traction motor control; to determine whether a belt is slipping; to detect skidding and automatically control braking.

Figure 1. Active speed sensor with coiled cable and connector. Source: Smith Systems, Inc.Figure 1. Active speed sensor with coiled cable and connector. Source: Smith Systems, Inc.

Passive speed sensors are a cost-effective way to monitor the number of shaft rotations, particularly a shaft that will run at a near-constant speed. They do not require a power supply, making them less complicated. Active speed sensors generate a digital square wave that can be used to determine rotational speed and direction of a shaft even at low speeds. Whether the assembly uses a toothed tone ring or a magnetic ring, Smith Systems, Inc. has cost-effective solutions for accurately measuring rotational speed.

Temperature sensors

Many system-critical components must be kept within the manufacturer’s temperature specifications. This is often a challenge in the transportation industry; blazing summer sunshine and proximity to hot engines cause temperatures to rise, and dust and mud can interfere with convective cooling methods. Monitoring the temperature of cooling fluids, electronic components, brake discs and other components is necessary for safe transit and long service life.

For these and many other temperature applications, Smith Systems, Inc. has developed a number of temperature sensors depending on the specific application and sensing environment. Their catalog includes thermocouples, thermistors, thermal-fuses, thermostats and resistance temperature detectors (RTDs). Regardless of the sensor type, each is housed in a durable, dustproof, shockproof probe.

Proximity sensors

Measuring the flow of a liquid, such as coolant or lubricating oil, can be tricky. The flow spins a turbine, which creates a pulse train signal. This signal can be calibrated to the flow rate, such that the higher the frequency of the pulse train, the larger the fluid flow rate. However, in order to get this measurement consistent and accurate, the turbine and sensing apparatus must not interfere with the measurement. Multiple magnets are required to improve the resolution for more accurate flow, but each magnet also adds drag to the system.

Smith Systems, Inc. has developed low-drag proximity sensors for such an application. Designed for use in magnetic flow meters, these proximity sensors guarantee more accurate measurements. They can also be used in metal parts counting on an assembly line, feedstock input and other manufacturing processes.

Smart control systems

Data acquisition and recording is often useful for diagnostic and troubleshooting purposes. However, somewhere in the process, there needs to be a decision made using this data. In the case of the lone sensor and data acquisition, decisions are made by a human operator. Consider the driver of an automobile who monitors the speedometer and presses the accelerator or brake, depending on the driving situation and the output of the speedometer.

Computers are better suited for decisions that must be made quickly, must be made in dangerous environments, are repetitive, boring, error-prone or high risk. Smith Systems, Inc. has developed a variety of smart control systems that can handle some of these decisions. Stop-motion sensing, overspeed or underspeed sensing, quadrature signals for determining rotational speed and direction are all used in the transportation industry.

For example, consider the comparison of rotational speeds on multiple wheels on an automobile. If these four wheels are not spinning at similar speeds, the vehicle is likely skidding, and thus the automatic braking system (ABS) needs to take over the braking control.

Cabling and connectors

With numerous sensors and control systems on the market, Smith Systems, Inc. also provides cabling and connectors for these systems. They can also reengineer cables and connectors for legacy systems where these components may be scarce or no longer commercially available. Their EZ-Change cabling and connector system combines the flexibility and strain relief to allow free movement of components with the ruggedness of an all-weather, all-temperature system. It is capable of operating in the cold, upper regions of the atmosphere as well as the hot under-hood environment of a race car.

Figure 2. Sensors, cabling, probe housings and connectors can be produced in-house. Source: Smith Systems, Inc.Figure 2. Sensors, cabling, probe housings and connectors can be produced in-house. Source: Smith Systems, Inc.

Overcoming supply chain pain

Even a quick glance at the news headlines shows how supply chain issues have impacted virtually every manufacturing and industrial facility. Between the COVID-19 pandemic, health orders, geopolitical turmoil and other factors, critical electronic components are not reaching manufacturers. Most electronic components have a long lead time due to these complications. Furthermore, some components are simply no longer available, and substitutes are required. Unfortunately, some of these substitutes are untested by safety and compliance standards and create even more delays from arrival to system implementation.

More than ever, there is a need to “reshore” some of these critical supply lines, such as semiconductors, sensors and electronic control hardware. Reshoring means switching from internationally sourced supply lines to domestically produced products that are less susceptible to political turmoil abroad. The recently passed CHIPS Act will invest money toward this effort, as have investments from Intel, TI and other domestic semiconductor manufacturers. The lack of semiconductor production and innovation has become a matter of national security.

Because Smith Systems, Inc. research, development and manufacturing is performed in North Carolina, they are ahead of reshoring efforts. Other companies may be scrambling to build new manufacturing facilities or expand existing ones, but Smith Systems, Inc. is already running industrial scale production numbers for sensors. This keeps lead time shorter and prices lower than many competitors.

Smith Systems, Inc. advantages

One of the secrets to their success is the ability to pivot to meet customer needs. Instead of simply producing a part and trying to explain how it will fit with a customer, they listen to the customer’s complaints about existing components and needs. Then, they redesign, source and test components in-house, providing solutions to fit their customers’ actual requirements.

Their production facility reduces the reliance on international supply lines. They also have overmolding capabilities for cables and connectors. This means they are well-positioned to deliver components, regardless of the turmoil between Russia and Ukraine, and Taiwan and China, both of which are impacting all of these supply chains. Ultimately, their customers see much smaller lead times on components at a lower cost.

Figure 3. Close up of a sensor and housing. Source: Smith Systems, Inc.Figure 3. Close up of a sensor and housing. Source: Smith Systems, Inc.

Case study: Train cables

A major train company lost its supplier of electrical cables that connected passenger train cars. The older cables were beginning to wear out, and they had been discontinued by the OEM. Even if the train company was willing to buy all new cables, they could not convince the company to start manufacturing the cables again. Not only were the cables no longer available, but the company that produced the connecting pins had discontinued these components as well.

The cables themselves were not a simple design. The cable assembly is 8 inches in diameter, containing 56 individual cables, all housed in a weatherproof housing, with connectors that were weatherproof and tolerant of vibration.

Smith Systems, Inc. reengineered the cables, found a new source for the connecting pins, and was able to deliver the cable assemblies to the customer in a quick and cost-effective manner. This kept their passenger fleet on the road, safely.

Case study: Mining equipment traction motor sensors

Traction control in large mining equipment is managed through individual motors that drive each wheel. For example, a four wheeled hall truck may have four separate traction drive motors so that each wheel can be driven separately. It is an efficient way to handle heavy loads, as the power output to each wheel can be individually controlled, applying the proper braking and acceleration to keep the haul truck upright and minimize brake fade.

For one large international mining company, these drive motors routinely failed. Each one cost approximately $3,000, leading to expensive repairs. Furthermore, the failure of one of these drive motors could create an exceptionally dangerous situation for a haul truck. Part of the problem was the failure of the OEM motor sensors used to monitor the motor performance and health.

Smith Systems, Inc. examined the failure modes of these traction motor sensors and reengineered them. The improved sensors lasted much longer, leading to less maintenance downtime and improved safety. The final cost for each of these redesigned sensors was approximately $600, or 20% of the cost of the OEM. This was made possible through their communications with the customer, learning their needs, then designing and building a customized solution.


Smith Systems, Inc. recognizes the importance of quick and precise monitoring and has designed sensors for the rugged environment found along the roads and rails. For more information on how to benefit from improved sensor performance in this time of supply-side struggles, contact or visit the website today.