When selecting a moisture meter, accuracy is a paramount concern. However, one model, the Extech MO280, exhibits a critical flaw: its very low score for accuracy when compared to most other wood moisture meters tested. This meter demonstrates significant inaccuracy when measured against ASTM D-4442 oven dry measurements.
Following the application of slight moisture to wood, the Extech MO280 displayed extremely inflated readings. The influence of temperature on readings was also notable. At a low meter temperature of 34.8° F, a slight increase in moisture content (MC) resulted in a 1% reading increase compared to room temperature (70.5° F). Conversely, at a high meter temperature of 110° F, the same low MC condition led to only a 0.2% reading increase relative to room temperature. Similarly, a low wood temperature of 33.6° F with low MC yielded a reading only 0.1% higher than at room temperature (71.8° F). Interestingly, a high wood temperature under low MC conditions produced the same reading as at room temperature.
Ease of Use and Durability
Despite its accuracy issues, the Extech MO280 is simple to operate, requiring minimal use of the manual to get started. It is constructed to be solid and durable, suggesting it is unlikely to malfunction or break with normal use. The meter is lightweight and comfortable to hold, featuring rubberized grips along the sides. Its compact design allows it to fit comfortably into a jacket or shirt pocket.
Features and Specifications
This is a single-mode meter, operating exclusively in a pinless mode, which is typical for this type of device. It includes a built-in species adjustment feature for specific gravity, offering ten categories for wood and other materials. The manufacturer states that the meter is effective on a variety of building materials. According to the manual, the measurement range is from 0.4% to 63.2%, though this range can vary slightly depending on the species group. Readings are precise to the nearest 0.1%.
Additional features include a low battery indicator and a HOLD function. This function "freezes" readings on the display, which is particularly handy when working in tight or difficult-to-see spaces. The manufacturer also states that the meter measures up to 3/4" deep.
Customer Support and Warranty
Customer service for the Extech MO280 appears knowledgeable, capable of answering basic questions regarding repair costs and turnaround times. The meter comes with a 1-year warranty, although the repair warranty is limited to 60 days.
Alternative: Klein Tools ET140 Pinless Moisture Meter
For those seeking a more budget-friendly option, the Klein Tools ET140 Pinless Moisture Meter, available for approximately $40, offers a different approach. While not expected to deliver exceptional accuracy at this price point, it aims to provide consistent results for tracking wood drying progress. Initial tests on various woods in a shop environment suggest consistency for a given species.
Performance of the Klein Tools ET140
For specific wood types, the Klein Tools ET140 reported the following moisture content levels:
- Cherry, walnut, and oak: 5-6%
- Maple: around 8%
- Softwoods: around 4%
- Pressure treated wood: around 10%
The meter includes settings for multiple materials: Hardwood, Softwood, Masonry, and Drywall. The "Hardwood" setting was used for the measurements listed above. The "Hold" button on this meter is also a useful feature, allowing users to place the meter on wood or between boards where visibility is limited and then retain the reading until the button is pressed again. Measurements are practically instantaneous.
Overall, the Klein Tools ET140 shows promise as a useful tool for monitoring the drying process of wood, particularly for users who prioritize consistency over absolute precision.