The worst question about a professional moisture meter is the one that never gets asked.
Even with years of experience using a commercial-grade device, questions still come up, especially around how to use a moisture meter and what you might run into during an inspection.
To help, we’ve gathered the most common questions we hear and answered them all in one place.
10 Moisture Meter FAQs Answered
Here are the most common questions we get when it comes to using a professional moisture meter: (click each question to jump to its answer)
- How does a moisture meter work?
- How do you use a moisture meter?
- How do you calibrate a digital moisture meter?
- Can a moisture meter detect mold?
- Can a moisture meter read through tile?
- How much does a moisture meter cost?
- Are pinless moisture meters affected by metal?
- Why does pin mode read high and pinless read low?
- Why does a pinless meter show a reading in air?
- How do I break fewer hammer needles?
1. How Does a Moisture Meter Work?
A base-level question, but a great starting point. We'll tackle this one by meter type:
How Does a Pin-Type Moisture Meter Work?
A pin-type moisture meter works by using electrical resistance to measure the moisture content of a material.
When the meter's pins (electrodes) make contact with the surface of the material being tested, they complete an electrical circuit. The meter then sends a small electrical current through the material between the two pins. The electrical current encounters resistance from the material's molecules, which varies depending on the material's moisture content.
In simplest terms: as water is conductive, the less resistance, the higher moisture readings are.
Further Reading:
- Professional Moisture Meters & Wood Species Calibration
- WME/Wood Moisture Equivalent: A Home Inspector's Guide +Chart
How Does a Pinless Moisture Meter Work?
Pinless (or non-invasive) moisture meter uses radio frequencies that penetrate the material being tested within its depth of measurement. The waves cause the material's molecules to vibrate and produce a secondary electromagnetic field that is detected by the meter.
The strength of the secondary field is proportional to the amount of moisture present in the material, allowing the meter to identify areas where moisture concentration is higher.
Pinless meters serve a few purposes, allowing for:
- A fast initial inspection to determine the locations of potential moisture problems
- Identifying moisture presence in areas otherwise impossible to check, e.g. behind tile walls, underneath laminate flooring.
Keep in mind, a non-invasive meter's readings are qualitative and require further investigation with a pin-type meter to confirm moisture presence.
2. How Do You Use A Moisture Meter?
Another base-level question, but a good one.
Let's break this down by meter type again.
Using a Pin-Type Meter
Giving readings for actual moisture content, pin-type meters take measurements by direct contact with a material.
To take a reading, simply touch the meter's probes to the material being tested and wait a few seconds for the device to display a measurement.
The #1 thing about taking pin-type meter readings: Do not jam the pins into the material you're testing. Not only does that potentially damage the probes, but it also increases the chances of an erroneous reading.
Using a Pinless Meter
Pinless meters measure moisture presence by using radio frequencies to detect areas with a high likelihood of moisture within their depth of measurement.
To take a reading, place the meter to the surface of the area being tested and allow a few seconds for a reading.
Non-penetrating meter readings do not give 100% confirmation of moisture. Rather, they help you hone in on areas that should be investigated further.
3. How Do You Calibrate a Digital Moisture Meter?
An important part of meter maintenance to ensure accurate measurements, calibration is a quick and easy process. It should be done at least every six months.
Again, let's look at this by meter type:
Verifying the Calibration of and Re-Calibrating a Pin-Type Meter
A process that also takes a few seconds, you'll need a calibration verification device – a moisture content standard (MCS) – designed specifically for your meter to measure resistance. Most pin-type meters come with one.
To check the calibration of your pin-type meter, touch its pins to the contact points on the MCS and wait a few seconds. Your meter should display a reading for a wood moisture equivalency of +/- 18.3% (in Protimeter instruments).
If your reading is outside that range, there’s likely an issue affecting your meter’s ability to take accurate measurements.
Additionally, newer models like the SurveyMaster BLD5375, Digital Mini BLD5775, and TimberMaster BLD5675 perform automatic recalibration after 50 on-off cycles, with no action required from the user.
Verifying the Calibration of and Re-Calibrating a Pinless Moisture Meter
For this, the best approach we find is to place the sensor on your skin directly. You should see a reading in the high 900s if not 999.
Our newer models, including the SurveyMaster BLD5375 and Aquant BLD5770, include built-in automatic in-air recalibration after 50 on-off cycles. The user is prompted to either skip the calibration or to proceed. Then a set of instructions are provided as if the user had initiated their own in-air calibration confirming to hold the meter in the air away from any people or surfaces. Contact with a hand during this process will affect the reading, typically shifting it from 999 to somewhere between 100 and 300. This can be corrected by repeating the in-air calibration and keeping the sensor away from objects and people.
4. Can a Moisture Meter Detect Mold?
An interesting question, to be sure.
In short, no.
However, a moisture meter – both pinless and pin type – is helpful in identifying where mold can be. Mold loves moisture and thrives in its presence. Using a moisture meter, you can zero in on areas to investigate where mold has already made a home or is likely to.We have recently developed a tool that provides an assessment of mold risk. It works best when used alongside surface temperature, humidity measurements, and moisture content, and can be used with Protimeter moisture meters, ProtimeterConnect.com for Bluetooth-enabled devices, or manual data entry.
You can check out the tool here: https://protimetermoldrisk.lovable.app/ and stay tuned for additional content on getting the most out of it.
5. Can a Moisture Meter Read Through Tile?
Yes! But only a pinless meter can because it uses radio frequencies to measure beneath the surface of the area being surveyed.
And again, be mindful of the type of reading you'll get – it's qualitative and would require further investigation to confirm moisture presence.
6. How Much Does a Moisture Meter Cost?
A professional moisture meter is indeed an investment. They can run several hundred to even several thousand dollars – a far cry from the $20 meters a homeowner might buy to have in their toolbox.
But an investment in a professional-grade meter shouldn't be looked at through solely the lens of money. Why? Because you're also investing in a few other important things:
- Better diagnostics – Made with sophisticated and highly reactive sensor technology, professional meters can take more precise readings.
- Reliability – With better readings, a professional meter provides accurate, consistent, and repeatable results every time.
- Saving time – Having accurate and reliable results means you won't have to double back after an inspection is completed to re-measure.
- Longevity – Professional-grade moisture meters are made with high-quality components and are designed to last decades.
7. Are Non-Invasive Meters Affected By Metal?
Yes.
Because moisture normally has a gradient from high to low, you should survey the area carefully and look for changes with a pinless meter. If you are getting consistently high readings, this could be caused by metal below the surface.
Always confirm the presence of excessive moisture with a pin-type meter or deep wall probes.
Typical behind-the-surface metals include corner beading and metal tile lathing.
8. Why Does Pin Mode Read High And Pinless Read Low?
This is typical of a condensation problem. Condensation is one of the major causes of moisture problems in buildings and is typically a surface moisture problem.
Non-invasive measurements give an average reading across the depth of measurement (up to ¾”), and pins give the highest reading for the depth of measurement (surface).
In the case of surface condensation, non-invasive mode will only show a slight increase in readings, and the pins will read high.
9. Why Does A Pinless Meter Show A Reading In Air?
This is typical of a temperature condition that is outside of the calibrated range. Refer to your instrument’s instruction manual.
10. How Do You Break Fewer Hammer Probe Needles?
To maximize the life of the electrode, and stop them from snapping, ensure that you drive the probes in straight, and most importantly, use the slide hammer action to drive the probes out straight.
If they do break, they can be easily replaced by disconnecting the base.
Wrapping Up Your Moisture Meter Questions
Knowing how to use a moisture meter comes down to understanding how it responds in real-world conditions. Readings can shift based on material type, depth, and surface conditions, so a consistent approach makes a difference.
These FAQs give you a clearer path during inspections and help you make sense of unexpected readings. When something looks off, it often points to an area worth a closer look.
With the right techniques and a bit of practice, you can work more confidently and get dependable results.
Find the Right Moisture Meter for You
Not all moisture meters are built for the same job. Compare options by function and application to choose the tool that fits your workflow.
Editorial note: This article was originally published in June 2023 and was recently updated to reflect current industry trends