In some respects, a professional moisture meter is a counterpart of sorts for home inspections or water damage restoration.
Dependable and manufactured to work with you, the device – whether pin or pinless – enables you to locate moisture and determine its extent of presence.
However, sometimes, even if you’ve taken excellent care of the device, a moisture meter’s accuracy may be noticeably off.
Like any other measurement tool, professional moisture meters (although rarely) can fall victim to issues that affect their ability to take accurate readings. When this happens, ignorance isn’t bliss – continuing to take measurements all but guarantees a survey that isn’t accurate.
Knowing the signs of accuracy issues in pin-type and pinless moisture meters, as well as their causes, helps ensure the integrity of a moisture survey’s results.
The Top 3 Signs a Professional Moisture Meter’s Readings Are Inaccurate
A highly sensitive measurement device, a professional moisture meter’s accuracy is critical for locating moisture and evaluating the degree of an intrusion. Small reading inaccuracies can have a big impact on the final results of an inspection.
When a meter’s readings are questionable, there are three sure-fire ways to know the device is not taking accurate measurements:
- Inconsistent readings on the same material
- Readings differ greatly compared to other meters
- Visible damage to the meter
1. Inconsistent Readings on the Same Material
The golden standard for verifying a moisture meter’s accuracy is to test the same material multiple times. If the meter is functioning as it should, moisture level readings taken in succession from the same material will have virtually no difference.
2. Readings Differ Greatly Compared to Other Meters
Along the same lines as our previous point, a sure sign that your meter is inaccurate is when its readings don’t match those of others. The same goes for ambient environmental conditions if you’re using a meter with a built-in hygrometer.
While there are nuances in the measurement scales of meters made by different manufacturers, readings taken by different meters (when adjusted) should be within the same range of each other. In other words, moisture content measurements should vary nominally between meters, regardless of their manufacturer.
3. Visible Damage to the Meter
One of the most obvious signs that your meter is giving inaccurate readings is through a quick inspection for damage. If a meter has taken a hard enough hit to cause visible damage – such as cracks in the case – or you can hear pieces moving around inside the device, odds are its measurements are no longer reliable.
Environmental Factors That Affect Moisture Meter Accuracy
While there are various reasons for a professional moisture meter’s readings to be slightly off, the majority stem from environmental factors.
The most common include:
- Salts
- Metals
- Material temperature
- Surface condensation
Salts
A naturally occurring substance that travels well with moisture, salt presents itself on materials where moisture is present. It’s most often seen as buildup on concrete flooring or along walls where moisture has leached through.
Salt is problematic for taking moisture readings with a pin-type meter for two reasons:
- It increases water retention within a substance
- It affects water’s conductivity
In both cases, salt impacts a pin-type moisture meter’s ability to take an accurate moisture reading.
Metal
In modern construction, buildings are made using a wide variety of materials, with metal being one of the most predominant. Whether it’s screws, nails, pipes, wires, or support beams, metals can give false/positive readings for both pin-type and pinless moisture meters.
For pinless moisture meters, direct contact with metal to their probes gives readings that the material is wet. While non-penetrating moisture meters measure moisture in a different way for a different purpose, metal also interferes with their ability to detect moisture’s presence, resulting in false-positive readings.
Material Temperature
A material’s temperature is particularly troublesome for pin-type moisture meters.
Why? Pin-type meters measure moisture through electrical conductivity and resistance.
When a material, such as wood, is warmer than the surrounding ambient temperature, its electrical conductivity increases, resulting in a higher moisture value measured by the meter. The inverse of this is true for colder temperatures.
Surface Condensation
Hand-in-hand with temperature comes surface-level condensation. When there’s a difference in temperature between the ambient environment and a material being tested, a thin film of moisture can form.
On lower-grade moisture meters (think the $20 devices sold at big-box retailers), surface-level moisture affects readings for both pin-type and non-invasive meters, resulting in measurements of far more moisture than actually present.
Troubleshooting an Inaccurate Moisture Meter
There’s nothing more frustrating than being in the midst of a moisture inspection and having your professional moisture meter not work like it’s supposed to – especially when taking readings.
The best way to avoid being caught with an inaccurate meter is to be proactive. Before heading to a job site, a few simple tests can clue you in to the state of the meter’s functionality. Those same tests can also be run on-site, too.
When verifying a meter’s accuracy, you should:
- Take readings on a known dry material to establish a baseline dry standard
- Take humidity and temperature readings to understand ambient environmental conditions
- Test materials with known moisture content and compare measurements
- Inspect the meter for obvious damage
- Check the meter’s battery status
If all else fails and the accuracy of your moisture meter is still in question, contact its manufacturer.
Professional Moisture Meter Accuracy & Reliability
In both home inspections and flood damage restoration, precise measurements are the most critical factor for addressing a moisture issue. Having a consistently accurate moisture meter makes this possible.
Regardless of the type of meter you’re using, knowing the signs for and how to troubleshoot inaccurate readings helps you paint a true portrait of moisture within a space.
Measure Moisture in Any Building With Confidence
Check out our downloadable guide, How to Measure Moisture in Buildings, to learn about the finer points of inspecting for moisture.
