Common Condition Monitoring Sensors & Techniques

Condition monitoring is the foundation of predictive maintenance, giving organizations the ability to anticipate equipment failures before they happen. Instead of reacting to breakdowns, condition monitoring allows maintenance teams to track the ongoing health of critical assets and act only when needed. The result? Less downtime, lower costs, and longer asset lifespans.

At the core of condition monitoring are sensors and data collection techniques that capture key indicators of machine health. By combining this information with an Industrial IoT (IIoT) platform, manufacturers and industrial organizations can scale monitoring across plants, facilities, or even global operations.

In this post, we’ll explore the most common types of condition monitoring sensors and techniques used today, how they work, and the value they deliver.

Why Condition Monitoring is Essential for Predictive Maintenance

Industrial equipment is constantly under stress—rotating at high speeds, exposed to extreme heat, pressure, and vibration, or running continuously for thousands of hours. Even the most well-designed machines eventually degrade. The challenge is knowing when that degradation is approaching failure.

Condition monitoring solves this by:

• Detecting early warning signs of problems
• Providing real-time insights into machine performance
• Enabling predictive maintenance instead of reactive repairs
• Extending equipment lifespan and reducing replacement costs
• Improving overall operational efficiency and safety

The types of sensors and techniques you use depend on your equipment and environment. Below are the most widely used approaches.

Types of Condition Monitoring Sensors

1. Electrical Condition Monitoring Sensors

Electrical sensors measure signals such as current, voltage, and power quality. They help identify imbalances, overloads, or faults that could indicate problems with motors, drives, or wiring.

• How it works: Current transformers and other sensors measure electrical load and performance.
• What it detects: Motor degradation, insulation faults, abnormal loads, or power quality issues.
• Applications: Motors, drives, electrical cabinets, and critical control systems.

By catching electrical anomalies early, organizations can prevent failures that could damage both equipment and safety.

2. Acoustic and Ultrasonic Monitoring

Acoustic condition monitoring listens for sound waves and vibrations outside the range of human hearing.

• How it works: Ultrasonic sensors detect high-frequency sounds that indicate issues.
• What it detects: Air or gas leaks, steam trap failures, arcing in electrical systems, early bearing wear.
• Applications: Pneumatic systems, valves, bearings, and steam systems.

Ultrasonic monitoring is particularly valuable for identifying compressed air leaks—one of the most common sources of wasted energy in manufacturing facilities.

3. Temperature Sensors for Equipment Health

Excess heat is one of the most universal signs of equipment trouble.

• How it works: Contact sensors (like thermocouples or RTDs) and non-contact infrared sensors measure surface or component temperature.
• What it detects: Overheating caused by friction, lubrication failure, or electrical faults.
• Applications: Bearings, motors, compressors, gearboxes, electrical panels.

Continuous temperature monitoring ensures hot spots don’t go unnoticed and helps protect both equipment and personnel.

4. Vibration Monitoring Sensors

Vibration analysis is one of the most well-established condition monitoring techniques, especially for rotating machinery.

• How it works: Accelerometers and vibration sensors measure frequency, amplitude, and patterns of motion.
• What it detects: Misalignment, imbalance, looseness, bearing wear, and gear defects.
• Applications: Motors, pumps, fans, gearboxes, turbines.

Because so many machine faults show up first as vibration, this technique is a cornerstone of predictive maintenance strategies.

5. Oil and Lubricant Analysis Techniques

Lubricants don’t just keep machines running smoothly—they also carry valuable information about equipment health.

• How it works: Inline sensors or periodic sampling track lubricant quality, contamination, and particle content.
• What it detects: Metal particles indicating wear, moisture intrusion, viscosity changes, or contamination.
• Applications: Gearboxes, hydraulic systems, engines, compressors.

By analyzing oil and lubricants, companies can catch issues like bearing wear long before they become catastrophic failures.

6. Pressure and Flow Monitoring Sensors

Fluid and pneumatic systems rely on consistent pressure and flow. Deviations are often the first sign of trouble.

• How it works: Sensors measure system pressure, flow rates, and differential pressure across components.
• What it detects: Leaks, blockages, declining pump efficiency, valve issues.
• Applications: Hydraulic systems, pumps, pipelines, compressed air systems.

Monitoring pressure and flow not only prevents downtime but also optimizes energy efficiency and system performance.

7. Visual and Infrared Condition Monitoring

Sometimes the simplest inspection methods provide the biggest insights, especially when enhanced with modern tools.

• How it works: Cameras and thermal imaging devices capture visual and infrared data.
• What it detects: Hot spots in electrical systems, insulation breakdown, mechanical misalignment, cracks or surface wear.
• Applications: Electrical cabinets, motors, rotating equipment, structural inspections.

Infrared imaging is fast, non-invasive, and can often be performed while equipment is still running—making it an efficient tool for preventive inspections.

8. Using System and PLC Data for Monitoring

Many machines already generate valuable performance data that can be tapped for condition monitoring.

• How it works: Data from PLCs, controllers, and onboard sensors is collected and centralized.
• What it detects: Run times, cycle counts, error codes, maintenance history, and operating patterns.
• Applications: Any industrial system with built-in control and monitoring features.

Leveraging existing data reduces the need for additional hardware and creates a more complete picture when combined with dedicated sensor inputs.

Matching Sensors to Equipment

Most programs start with one or two measurements per machine and add more once the first data shows where problems are. This table is a starting point for common industrial equipment.

Equipment	Common failures	Sensors to start with
Electric motors	Bearing wear, overload, winding and insulation faults	Vibration, current, temperature
Pumps	Cavitation, seal leaks, bearing wear, clogging	Vibration, pressure, flow, current
Fans and blowers	Imbalance, belt wear, bearing wear	Vibration, current
Gearboxes	Gear and bearing wear, lubrication breakdown	Vibration, temperature, oil condition
Air compressors	Leaks, overheating, valve wear	Pressure, temperature, current, ultrasonic
Hydraulic systems	Leaks, contamination, pump wear	Pressure, oil condition, temperature
Electrical cabinets and drives	Loose connections, overheating, power quality	Temperature or infrared, current, voltage
Valves and steam traps	Leaks, sticking, failed traps	Ultrasonic, temperature, position
Heavy mobile equipment	Engine and hydraulic wear, overloading	Controller data (hours, fault codes, load), vibration, oil condition

Machines with a PLC or onboard controller often already record run time, cycle counts, loads, and fault codes. Reading that data first is the cheapest way to start, and dedicated sensors fill in what the controller doesn’t measure.

Choosing Sensors for Harsh and Outdoor Environments

Equipment in fields, mines, water plants, and on mobile machinery puts more demands on sensors than a climate-controlled factory floor. Check these before choosing hardware:

• Ingress protection: IP67 or IP68 for sensors exposed to rain, washdown, or dust.
• Operating temperature: the rated range should cover the coldest night and hottest surface on the equipment, not just ambient air.
• Hazardous locations: sites with flammable gas or dust need certified hardware (such as Class I Division 2 or ATEX).
• Connectivity: cellular or LoRaWAN gateways for remote sites without plant networks; wired sensors where vibration, interference, or data rates rule out wireless.
• Power: battery-powered wireless sensors trade sample rate for battery life, so confirm the reporting interval still catches the failures you care about.
• Mounting: stud-mounted vibration sensors give more reliable readings than magnetic mounts on equipment that sees shock.

Where to Get Condition Monitoring Sensors

Industrial sensor manufacturers and automation distributors sell most of these sensors individually. Several vendors also sell wireless sensor kits that come with a gateway, which is often the fastest way to retrofit existing equipment. Equipment makers increasingly build sensors into new machines at the factory so monitoring is available from the first day of operation.

Exosite is hardware-agnostic: data can come from PLCs, industrial and cellular gateways, or wireless sensors, and lands in the same dashboards and rules. See condition monitoring with Exosite for how equipment makers put this together.

Benefits of Using an Industrial IoT Platform for Condition Monitoring

While each of these techniques provides value, the real power of condition monitoring comes from combining them in a centralized platform. This is where an Industrial IoT platform like Exosite’s delivers benefits in scale, robustness, and security.

• Scale: Collect data from thousands of assets across multiple facilities and unify it in the cloud.
• Robustness: Ensure reliable data handling with high-frequency time-series databases, real-time rules engines, and resilient integrations.
• Security: Protect sensitive operational data with enterprise-grade encryption, secure device onboarding, and role-based access.

By bringing together data from electrical, acoustic, temperature, vibration, oil, pressure, flow, and visual techniques, organizations can move beyond reactive maintenance into a proactive, predictive strategy that drives measurable ROI.

Learn More: Condition Monitoring Software for Equipment Makers

Final Thoughts: Moving Toward Predictive Maintenance

Condition monitoring is no longer optional—it’s a necessity for organizations looking to stay competitive in modern industry. By deploying the right combination of sensors and monitoring techniques, and centralizing that data on a secure, scalable IIoT platform, businesses can:

• Reduce unplanned downtime
• Extend equipment lifespan
• Lower maintenance costs
• Improve safety and compliance
• Optimize overall operational performance

The future of industrial maintenance is predictive—and it starts with condition monitoring.

Learn More: Condition Monitoring Solutions with Exosite

Frequently Asked Questions About Condition Monitoring Sensors

What are the most common condition monitoring sensors?

The most common condition monitoring sensors include vibration, temperature, acoustic/ultrasonic, oil and lubricant analysis, electrical, pressure and flow, and visual/infrared sensors. These measure different aspects of machine health to detect early signs of failure.

Why is vibration monitoring important in condition monitoring?

Vibration monitoring is important because most mechanical issues—such as imbalance, misalignment, or bearing wear—show up first as abnormal vibrations. Tracking vibration patterns helps identify problems early and prevent costly breakdowns.

How does acoustic condition monitoring work?

Acoustic condition monitoring uses ultrasonic sensors to detect high-frequency sounds outside the range of human hearing. This technique is effective for spotting air leaks, steam trap failures, electrical arcing, or early bearing wear.

What role does oil analysis play in predictive maintenance?

Oil and lubricant analysis tracks fluid quality and contamination. Detecting particles, moisture, or chemical changes helps identify wear and prevent major equipment damage, especially in engines, gearboxes, and hydraulic systems.

Which condition monitoring sensors are best for heavy machinery?

Start with what the machine’s controller already reports, such as engine hours, loads, and fault codes. Add vibration sensors on rotating components, oil condition sensors on engines and hydraulics, and temperature sensors on bearings and gearboxes. Choose rugged, sealed sensors rated for shock and the full outdoor temperature range.

What sensors work in harsh, outdoor environments?

Look for IP67 or IP68 enclosures, an operating temperature range that covers the site’s extremes, and hazardous-location certification where required. Remote sites usually connect through cellular or LoRaWAN gateways rather than a plant network.

What are the benefits of using an Industrial IoT platform for condition monitoring?

An Industrial IoT (IIoT) platform makes condition monitoring scalable, robust, and secure. It unifies data from multiple sensors, provides real-time alerts, ensures data integrity, and enables predictive analytics across entire operations.