FLIR MR40 Moisture Meter - Reliable Moisture Detection for Home Inspectors

Published on Aug. 25, 2023, 6:10 p.m.

Detecting moisture accurately and quickly in buildings is crucial across various sectors, including construction, industrial inspections, and firefighting. Thermal imaging technology, particularly through thermal imagers, captures heat radiation from objects to convert it into a visible image, providing an effective tool for detection. The FLIR MR40 Moisture Meter is such a tool, combining thermal imaging with moisture detection to deliver precise moisture readings for professionals.

Detecting moisture issues in buildings quickly and accurately is crucial for home inspectors, contractors, and anyone involved in building maintenance. The FLIR MR40 Moisture Meter aims to provide easy and reliable moisture detection in a compact, rugged package. With a built-in flashlight and special audible alerts, this moisture meter seems well-suited for inspectors who need to take readings in tight spaces.

But does the MR40 live up to its promises for home inspectors and contractors? This review will examine the features, performance, and real-world usability of the FLIR MR40 based on hands-on testing and user reviews. Read on to see if this moisture pen should earn a spot in your toolkit.

 FLIR MR40 Moisture Meter with Flashlight


The FLIR MR40 is a compact, pocket-sized moisture meter designed for building professionals who need to quickly find and quantify moisture issues. Key features include:

  • 2-pin moisture detection with auto-calibration
  • Clear LCD display
  • Audible alerts for moisture level ranges
  • Built-in 40 lumen flashlight
  • IP54 splashproof rating
  • Replaceable pins and included spare set
  • Uses 2 AAA batteries (included)

With dimensions of just 0.5 x 0.4 x 7.6 inches and weighing 2.88 ounces, the MR40 is one of the smaller and more portable pinned moisture meters available. It’s meant to be carried in a pocket or pouch for easy access. The MR40 detects moisture levels from 5% to 60% in wood and common building materials.

Technical Background

Thermal imagers operate by detecting infrared radiation and converting this data into images, assisting professionals in identifying temperature variances. The FLIR MR40 not only detects moisture but also incorporates thermal imaging technology, enhancing the accuracy of detections. This instrument is particularly suited for building inspections, moisture intrusion detection, and other scenarios that require precise moisture readings.

 FLIR MR40 Moisture Meter with Flashlight

Design and Build Quality

The MR40 has a slender, pen-shaped housing that feels sturdy and durable. The base is knurled for grip, and the clear/translucent plastic body resists scratches. The meter is rated to withstand 3-meter drops, and the IP54 rating means it resists dust and splashing water.

The pins are metal and feel sturdy, without being overly sharp. The included spare set ensures you have backups ready. The battery door and cap secure solidly. Overall, the build quality is impressive for the price.

Features and Performance

A single button turns the MR40 on/off, and it has an automatic power-off function after 2 minutes to save battery life. The LCD is clear and easy to read, though lacking a backlight. The audible alerts are handy for quickly gauging moisture levels.

In testing, the readings were consistent and seemed accurate for common building materials. The pins penetrate surfaces well. The meter also performs an automatic calibration check when the cap is replaced.

The 40 lumen flashlight is relatively weak but can be helpful in dark areas. Just note it will drain the batteries faster.

One downside is the cap doesn’t secure tightly and can pop off easily. The exposed pins are a hazard, so take care when storing the meter.

Technical Analysis of Features

The technical specifics of the FLIR MR40 highlight its advantages in the field of moisture detection. Features like its auto-calibration 2-pin detection, clear LCD screen, and audible moisture level alerts stand out. Additionally, its IP54 water resistance rating and replaceable probes ensure the device operates accurately even in harsh environments.

Ease of Use

Overall, the MR40 is quick and easy to use. Simply touch the pins to the material, allow a second or two for the reading, and note the results. The meter beeps when first turned on and then based on the moisture level range. It’s easy to take successive readings.

The compact size makes the MR40 easy to maneuver in tight spots. Home inspectors appreciate being able to take pinpoint readings in corners, along baseboards, and other confined areas. It’s also handy for checking under sinks, around plumbing, and investigating water stains.

Accuracy and Reliability

In terms of accuracy, FLIR claims +/- 2% margin of error in the 5% to 30% moisture content range, increasing slightly in the 30% to 60% range. Based on hands-on testing, the readings aligned with expectations across various materials. The meter gives consistent results between tests.

Most reviewers find the MR40 reliable and suitably accurate for pinpointing the location and severity of moisture intrusions. The auto calibration feature helps maintain accuracy over time.

Use Cases:

  • Inspecting buildings, roofs, floors for moisture problems
  • Locating water leaks, moisture damage
  • Checking moisture levels in walls, carpets, insulation
  • Verifying and quantifying dampness issues
  • Ideal for builders, inspectors, contractors

 FLIR MR40 Moisture Meter with Flashlight

User Feedback Summary:

Positive feedback on accuracy, ease of use, value for money. Customers report it provides reliable measurements in tight spaces other meters can’t reach. Durable construction withstands drops.

Some complaints about the small screen being hard to read without backlight. Cap falls off easily. Flashlight not very useful.

Overall customers find it an affordable, pocket-sized moisture meter that gets the job done.


  • Compact size
  • Reasonably priced
  • Accurate and consistent readings
  • Rugged, durable construction
  • Audible moisture indicator
  • Easy to use


  • No backlight on display
  • Cap falls off easily
  • Flashlight not very useful


With reliable performance in a compact rugged design at an affordable price, the FLIR MR40 provides very good value for the price.

 FLIR MR40 Moisture Meter with Flashlight


The FLIR MR40 excels at delivering easy, reliable moisture readings in a highly portable package. It’s an affordable go-to moisture meter for home inspectors, contractors, and maintenance workers who need to quickly identify and estimate moisture issues.

The compact design and audible alerts make the MR40 uniquely suited for use in tight, dark spaces common in inspections. While the flashlight and cap need improvement, the solid performance and accuracy are impressive for the price.

Overall, the FLIR MR40 earns a recommendation as an excellent moisture pen for building professionals who rely on convenient, rugged moisture detection. It provides ample versatility and accuracy for inspectors who need reliable moisture readings on the go.


  • Measurement Range: 5% - 60% moisture content
  • Accuracy: +/- 2% from 5% to 30% MC; +/- 5% from 30% to 60% MC
  • Operating Temperature: -10°C to 50°C
  • Power: 2 AAA batteries (included)
  • Dimensions: 18mm diameter x 190mm length

What’s in the Box:

  • MR40 moisture meter
  • 2 AAA batteries
  • Spare pin set
  • User manual


  • Press button to turn on
  • Insert pins into material
  • Read moisture level on display
  • Listen for audible indicator
  • Hold meter in place until reading stabilizes