Manufacturing technology today offers more access to real-time performance metrics and monitoring than ever before. Why is this important? With more data on hand — delivered in real-time, as equipment operates — manufacturers have more tools at their disposal to make operational decisions, reduce downtime and protect equipment from failure, malfunction and damage.
AC current sensors are one such tool, measuring the electrical current flowing through a circuit, with the ability to facilitate alarms and automatic shutoff in cases of overload and other adverse scenarios.
How does a current sensor work? An AC current sensor operates on the basis of the Hall effect, producing a magnetic field directly related to current strength, which is then amplified to provide an output measurement. This measurement forms the basis for any alerts and automated shutdown controls. There are numerous types of current sensors available based on this principle, which we will explore in greater depth next.
How do AC current sensors work?
AC current sensors operate by detecting magnetic fields generated by electrical current. Most sensors use the Hall effect, where a magnetic field is created in proportion to the flow of current. This field is converted into a measurable voltage signal that can be interpreted by control systems. This process enables the immediate identification of anomalies and supports prompt corrective action.
In many industrial systems, the voltage signal is transmitted to PLCs or centralized monitoring systems, where the data is analyzed for signs of abnormal current draw. Alerts can then be triggered, or shutdowns initiated, when thresholds are exceeded. This helps protect equipment, prevent unplanned downtime and ensure system-wide safety and efficiency.
Current sensors may also be embedded within larger condition monitoring frameworks, giving engineers visibility into performance trends. When used alongside temperature pressure, or vibration sensors, current data enhances diagnostic accuracy.
Motor current signature analysis is a powerful diagnostic technique that identifies faults in motors by analyzing current waveforms. These patterns can reveal issues like broken rotor bars, eccentricity or bearing wear — often before physical symptoms arise.
Types of AC current sensors
The two primary types of AC current sensor are open loop and closed loop sensors. Open loop sensors are driven by a Hall effect sensor placed in the air gap of a magnetic core, while closed loop sensors use a Hall effect generator in the air gap of a magnetic core, along with a coil around the core and a current amplifier.
Both types of sensors offer electrical isolation between the circuit and the output. Open loop sensors are generally lower cost, offering high accuracy and low power consumption, with potential risk for saturation and temperature drift. Closed loop sensors are resistant to drift and offer high linearity along with fast response times.
Open loop sensors are ideal for general industrial automation tasks where cost-effectiveness is important, and slight drift is acceptable. Closed loop sensors, on the other hand, are best used in precision applications requiring rapid feedback and minimal error, such as robotics, CNC machinery or sensitive test equipment.
Feature | Open loop sensors | Closed loop sensors |
Accuracy | Moderate | High |
Cost | Low | Higher |
Response time | Slower | Fast |
Temperature drift | Higher | Minimal |
Best use case | General industrial use | High-precision applications |
AC current sensor applications
AC current sensors can fulfill many applications in industrial facilities, offering extensive utility for any machinery or equipment that incorporates an electric motor. Current sensors can protect motors from overload, shutdown and damage by detecting excessive current conditions and triggering an alert. Sensors can also enable automatic shutdown — one of the most effective ways to prevent damage and the need for replacement motors. Even small, relatively inexpensive motors can negatively impact the bottom line if they lead to equipment downtime and require frequent maintenance and replacement.
They are especially important in mission-critical systems like conveyor belts, CNC machines, HVAC systems and automated packaging lines. These systems demand consistent uptime — and current monitoring helps achieve that by flagging irregularities in motor current before they lead to failure.
Current sensors in predictive maintenance
An effective predictive maintenance implementation can lead to cost savings, increased uptime, better performance for customers, and overall productivity and success metric improvements. This is because predictive maintenance uses real-time data to drive targeted decision-making with the flexibility to troubleshoot and take action without emergency shutdowns, but well before equipment malfunctions.
Current sensors play a role in predictive maintenance by enabling real-time monitoring of current. Beyond the ability to shut down equipment if an overload scenario occurs, in a predictive maintenance framework, current sensors can be used to identify the earliest signs of potential failure states. The more data collected, the more accurate and effective these readings will be.
Devices like a current transformer enable safe and accurate current measurement in high-power systems by stepping down the current to manageable levels for sensors and monitoring devices. A circuit breaker protects systems by automatically cutting off power when it detects fault conditions. A relay is another protective device that works in tandem with current monitoring systems; it triggers shutdowns or alarms when conditions exceed safety thresholds, helping facilities avoid damage and downtime.
Whether small or large, electric motors are foundational to industrial operations. Monitoring their performance with current sensors ensures optimized function, extended lifespan and fewer unexpected failures. When paired with current sensors, real-time alerts can prevent unplanned trips and support safer, more reliable operations. Monitoring the health of an induction motor, which is one of the most common motor types in industry, requires consistent analysis of current draw. Modern motor monitoring strategies rely on a blend of sensors — including current, thermal and vibration analysis tools — to detect early signs of wear, misalignment or imbalance, as early identification of potential motor failure is critical.
For example, if a technician observes a consistent increase in motor current draw over time, they may investigate signs of internal motor wear or alignment issues. This proactive approach helps avoid costly repairs and reduces inventory needed for emergency replacements.
In a true predictive maintenance implementation, equipment and technicians use predictive maintenance analytics to be alerted not only to imminent overloads, but to patterns that indicate that overloads are developing. This allows technicians to take preliminary action and schedule diagnostics and potential action. By reducing or eliminating a “run to failure” approach, predictive maintenance can also reduce inventory costs and extend the lifespan of equipment and components.
Additionally, current sensor data can be integrated with IIoT platforms, cloud analytics and remote monitoring tools. These technologies enable centralized control rooms to monitor large fleets of motors across facilities, helping prioritize maintenance schedules, minimize energy waste and extend motor lifespan.
Integrating current sensors into a condition monitoring plan
In a comprehensive condition monitoring strategy, current sensors are most effective when paired with other industrial sensors such as vibration sensors, temperature sensors and pressure sensors. This multi-sensor approach offers a holistic view of equipment health and operational status.
For instance, a spike in current combined with increased vibration and heat may signal a developing bearing failure. By detecting this combination early, technicians can intervene before the issue worsens. Centralized monitoring systems like CMMS platforms help visualize these sensor outputs and facilitate efficient decision-making.
A well-structured plan enables facilities to move from reactive to predictive operations — reducing labor hours, limiting costly downtime and improving reliability metrics across the board.
Partnering with ATS for predictive maintenance
Current sensors are just one component of an effective condition monitoring plan. By using current sensors in conjunction with other industrial maintenance sensors such as vibration, temperature, pressure and more, your facility and technicians can be prepared to address any potential maintenance challenges well before they lead to unplanned downtime and lost productivity. To learn more, contact ATS today.
