Keysight U5855A TrueIR Thermal Imager

Published on Aug. 3, 2023, 8:09 a.m.

Thermal imaging, a pivotal technology in predictive maintenance, allows professionals to visualize heat emanating from equipment or objects, transforming it into a digestible and actionable visual format. This introductory section delves into the fundamentals of how thermal imagers capture varying heat radiation from different objects, converting these variations into clear, visual representations. By understanding this, readers can appreciate the nuanced insights provided by devices like the Keysight U5855A TrueIR Thermal Imager in various industrial applications.

The Keysight U5855A TrueIR Thermal Imager is a professional grade infrared camera designed for predictive maintenance and troubleshooting applications. It features a 320x240 IR sensor resolution enhanced by fine resolution technology, temperature measurement range from -20°C to 350°C, image logging and trending capabilities, and compact and lightweight design.

 Keysight U5855A TrueIR Thermal Imager


The U5855A TrueIR Thermal Imager from KEYSIGHT Technologies builds on their experience providing test and measurement equipment. The 320x240 IR resolution is 4x higher than typical entry-level thermal imagers, revealing finer details in the thermal image. Combined with image logging and trending software, the U5855A is well-suited for predictive maintenance tasks.

Key Features

  • 320x240 effective IR resolution with fine resolution technology
  • Temperature range from -20°C to 350°C
  • Image logging and trending with TrueIR Analysis software
  • Lightweight and compact form factor
  • Intuitive touchscreen interface
  • Interchangeable batteries with up to 4 hours runtime

Technical Background of Thermal Imagers

Understanding the core principles behind thermal imaging is essential for grasping how devices like the U5855A operate. Thermal imagers detect infrared radiation emitted from objects, converting these data points into an image that visually represents temperature variations. Key performance indicators, such as resolution, sensitivity, and temperature range, are crucial for evaluating the efficacy of a thermal imager. This section will explore these technical aspects to provide a deeper comprehension of what makes the U5855A stand out in its field.

Design and Build Quality

The U5855A has a sturdy plastic construction that feels solid yet remains lightweight at 0.746 kg. The handgrip is covered in a textured rubberized material that provides a secure grip. The 3.5” LCD touchscreen is bright and responsive. Overall fit and finish is excellent as expected for a professional grade Keysight instrument.

Image Quality and Temperature Accuracy

Image quality is superb thanks to the fine resolution enhancement which sharpen details and eliminates noise. Small components in tight spaces can be easily inspected. Temperature accuracy is rated at ±2°C or ±2% which proved accurate during testing. The camera was able to discern small temperature differences.

Temperature Measurement Capabilities

With a -20°C to 350°C range, the U5855A can monitor temperatures for electrical, mechanical, and low-temperature industrial applications. Temperature accuracy is ±2°C or ±2%, providing reliable measurements. The U5855A also includes configurable temperature alarms and difference measurements to simplify analysis.

Features and Operation

The intuitive touchscreen interface provides quick access to all key settings. Image modes include IR, visual, and blended IR/visual. Temperature alarms, spot markers, and analysis tools allow quick identification of hotspots. The U5855A can store images to a removable SD card for later analysis. Battery life is adequate for a half day of scans before needing a recharge.

Diverse Applications of the U5855A Thermal Imager

The U5855A TrueIR Thermal Imager finds its utility in a multitude of fields, extending far beyond the typical industrial or mechanical inspections. In healthcare, it can be employed for body temperature screening or vascular health monitoring. In construction, it assists in identifying heat losses and leakages in buildings. The precision and versatility of the U5855A make it an indispensable tool across various domains, including but not limited to, electrical inspections, HVAC systems evaluation, and even in research settings where temperature plays a critical role in experimental outcomes.

Software and Connectivity

The included TrueIR Analysis software is easy to use for reviewing stored images, temperature trending, and report generation. It can also live stream video from the camera over USB. Standard USB and video out ports allow connection to a PC and external monitor.


Common applications include:

  • Electrical inspection - Find hotspots in panels, motors, or switchgear.
  • Mechanical inspection - Detect bearing or pump issues through abnormal temperatures.
  • HVAC/R inspection - Check insulation, ductwork, and system performance.
  • Process monitoring - Spot temperature variations in manufacturing processes.

User Feedback

The KEYSIGHT U5855A Thermal Imager has received largely positive feedback from customers and reviewers. Here is a summary of common pros and cons mentioned:


  • Excellent image quality and detail thanks to the 320x240 IR resolution
  • Accurate temperature measurements help spot faults and issues
  • Intuitive menu system and controls are easy to learn
  • Rugged, lightweight design is great for field use
  • Included analysis software is simple but powerful


  • Battery life is limited to about 4 hours of use
  • Temperature range could be wider for some industrial uses
  • High initial cost, though value is good for the performance

On Amazon, the U5855A has a 4.7 out of 5 star average rating. Positive reviews mention the image quality and how small details are easily visible. The ergonomic design and simple controls are also highlighted. One verified purchaser who uses it for electrical inspections says it has paid for itself by finding faults early.

The most common complaints focus on the battery life. A 4 hour runtime means having spares or an external pack for longer inspections. The narrow temperature range up to 350°C also limited use for some buyers. They wished for at least a 500°C range for more industrial applications.

 Keysight U5855A TrueIR Thermal Imager


The Keysight U5855A carries a list price around $4,000. While not cheap, it provides better image quality and temperature measurement performance than cheaper entry-level models. For those needing accurate thermal inspections, the U5855A delivers significant value.


The Keysight U5855A TrueIR Thermal Imager delivers excellent image quality and temperature accuracy in a flexible and lightweight package. It’s a great troubleshooting tool for maintenance engineers and technicians. The combination of high resolution, compact size, and robust software make it easy to spot anomalies and diagnose issues. Its capabilities and ease of use make it a worthwhile investment for advanced electrical and mechanical troubleshooting.

Brand and Service

KEYSIGHT is an industry leader in test and measurement equipment. The U5855A comes with a 1 year warranty and access to KEYSIGHT’s global service network. Calibration and extended warranty plans are available.

Future Prospects of Thermal Imaging

As we continue to innovate, the realm of thermal imaging holds promising advancements. Future iterations of thermal imagers may incorporate enhanced resolution, broader temperature ranges, and more sophisticated image processing algorithms. These advancements could open new doors for applications in sectors like environmental monitoring, advanced manufacturing, and autonomous vehicles, showcasing the evolving utility of thermal imaging technology in our ever-changing world.


  • 320x240 effective IR resolution
  • Temperature range: -20°C to 350°C
  • Accuracy: ±2°C or ±2%
  • Frame rate: 9 Hz
  • Field of view: 28° x 21°
  • Focus range: 10 cm to infinity

 Keysight U5855A TrueIR Thermal Imager

What’s Included

  • U5855A Thermal Imager
  • AC adapter and power cable
  • Rechargeable Li-ion battery
  • SD memory card
  • USB and video cables
  • Hard carrying case
  • Quick start guide

Usage Tips

  • Allow 2 minute warm up time for best accuracy
  • Adjust emissivity setting for each material scanned
  • Use image logging to capture temperature trends
  • Create inspection templates with annotations
  • Use TrueIR Analysis software for reporting