CRITICAL FLAW ALERT!
This meter exhibits two critical flaws—namely its very low score for accuracy and its inability to provide results below about 8-9% moisture content, even though the manual states it gives readings to 5% moisture content. These flaws render the meter essentially unusable for a number of common applications, including for flooring installations and furniture making. We deducted two stars from our overall rating to reflect these critical flaws.
The General MMH800 is both a pin-style moisture meter and a pinless meter that measures moisture using a pad sensor. It offers an easy-to-read digital readout. It is designed to appeal to the budget-conscious user and it is extremely simple-to-use.
However, this meter has significant limitations. Our tests indicate that the General MMH800 appreciably underestimates moisture content in wood, and actually scored lower for accuracy than any other meter we tested.
In addition, it is unable to take measurements below about 8-9%. Do not rely upon the MMH800 for measuring wood with low MC levels even though the manual states that it is able to take measurements as low as 5% MC.
It is designed for both wood and other building materials, but no adjustments are possible for different species of wood.
Pros
- Simple-to-use with large, easy-to-read LCD display
- Features data hold button and built-in calibration check
- Capable of measurements in a variety of building materials
Cons
- Unable to take readings below about 9% MC
- Significant accuracy issues
- No adjustment available for wood species
Objective Evaluation – Overall Score 2.25 out of 5.0
Accuracy – 0.67 out Of 5.0
This meter scored poorly for accuracy, with readings that were significantly lower than actual MC when compared to ASTM D4442 oven dry standards. This meter’s accuracy is questionable due to low readings across the entire range from low to high MC.
Learn about our accuracy test procedures
Surface Moisture – 1.0 out of 5.0
Surface moisture caused this meter to post readings over 15% higher than the baseline. These surface moisture results indicate that operating this meter in high humidity environments where condensation may form on the surface could lead to questionable readings.
Learn about our surface moisture test procedures
Meter Temperature – 1.0 out of 5.0
Meter temperature had a significant effect on this meter’s MC readings. A low meter temperature of 34.8° F in the presence of low MC increased the reading by about 2% compared to the room temperature reading. A high meter temperature of 110° F in the presence of low MC increased the reading by about 1% compared to the room temperature reading. In the presence of high MC, the reading increased by about 2%.
Learn about our meter temperature test procedures
Wood Temperature – 2.5 out of 5.0
Wood temperature affected this meter’s readings.
A low wood temperature of 33.6° F in the presence of low MC showed no appreciable change in the reading when compared to the room temperature reading. However, in the presence of high MC, the reading changed by about 3%.
A high wood temperature of 110° F in the presence of low MC showed a 1% increase in the reading when compared to the room temperature reading. In the presence of high MC, the reading decreased by about 9%.
Learn about our wood temperature test procedures
Reading Repeatability – 4.0 out of 5.0
The readings of this meter were not entirely repeatable, showing some tendency to vary.
Learn about our repeatability testing procedures
Drift – 5.0 out of 5.0
Readings for this meter showed little tendency to drift, with readings that were only slightly lower after three seconds.
Cable Interference – N/A
This meter does not offer cabled accessories so the cable interference test could not be conducted.
Learn about our cable interference and drift testing procedures
Subjective Evaluation – Overall Score 3.9 out of 5.0
Learn about our subjective testing procedures
Ease of Use – 3.2 out of 5.0
This meter is easy to operate. Four buttons means it is necessary to consult the manual in order to understand all the available options. Documentation provided in the manual is adequate, although no table is provided for making species adjustments.
Quality – 3.7 out of 5.0
This meter is intended for the budget-conscious individual, yet its appearance suggests quality. The meter’s casing and controls seem solid and durable. No carrying case is provided. The pins are not as subject to bending or breakage as with many other pin-style meters.
Comfort – 5.0 out of 5.0
This meter has an ergonomic design that is comfortable to hold, the display is easy-to-read and the four control buttons are a snap to use. No complaints here.
Versatility – 3.0 out of 5.0
This is a pin-style meter that also features a sensor pad for pinless moisture measurement. It is not capable of adjusting for species. Data must be viewed upside down while the meter’s pins are inserted into the wood sample, although this can be addressed by using the HOLD function.
Range – 5.0 out of 5.0
Measures moisture content from 5% to 50%, at least in theory. In practice, our tests indicated that no readings can be obtained below about 9% MC.
Features – 3.2 out of 5.0
Readings precise to the nearest 0.1%. Low battery indicator. Offers an easy calibration check and a HOLD function for use in tight spaces where the display cannot be easily viewed.
Customer Service – 4.0 out of 5.0
General offers free replacement if anything goes wrong in the first year. No service center is available for repairs, nor does General offer any calibration services for its meters. Response to telephone inquiries is fast and friendly.
Our review is based on Moisture Meter Experts independent evaluation of the meter, which was purchased by Moisture Meter Experts or provided free of charge by the manufacturer. By purchasing this meter through the links above, Moisture Meter Experts may be compensated either by your purchase directly from Moisture Meter Experts or from commissions from an affiliate. View our Review Procedures section to learn more about our proprietary evaluation procedure and expertise in the field of moisture meters.