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Protimeter · Protimeter Aquant Non‑Invasive Moisture Meter - BLD5770
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A non invasive moisture meter that reads up to 20 mm, three quarters of an inch, below a surface without marking it, sends time and date stamped readings over Bluetooth to the Protimeter Connect app for logging and export, runs three times longer than the model it replaces, and carries an automatic calibration check alongside a user field calibration. It is a comparative instrument, and the listing never publishes what the display actually reads: no scale, no units, no range and no accuracy. That matters less than it first appears, and it changes what a reading entitles you to conclude.
A relative scale, and the units the listing never names
Start with how a non invasive head works, because the missing scale follows directly from it.
The instrument generates a radio frequency electric field at its measuring face and projects it into the material. It then measures the dielectric response of everything inside that field. Water has a dielectric constant many times higher than dry timber, plaster, screed or concrete, so the more water sits inside the field, the larger the response. That is the whole measurement.
What it cannot produce is a moisture content by mass. To do that an instrument would need to know the density, the composition and the thickness of what it is looking at, and a head pressed against a painted wall knows none of those. A pin meter can be related to timber moisture content because it measures resistance between two electrodes at a known depth in a single known material, with a correction for species. A capacitance head reads an unknown volume of unknown constituents.
So an instrument of this type is comparative by construction, not by cost saving. The correct technique follows from that:
- Find an area of the same material and the same construction that you are confident is dry.
- Take a reference reading there.
- Survey outward and map where the response rises above it.
- Treat the pattern as the finding, not any individual number.
The listing never explains this, and it should, because a buyer expecting a percentage will misread the instrument on the first job and conclude the meter is broken. What the bullets do get right is the vocabulary: they describe moisture mapping, which is exactly the right phrase and tells you how the tool is meant to be used. Our comparison of pin against pinless meters covers which questions each type can answer.
Twenty millimetres is a depth and an average
Credit the figure first. A stated depth of 20 mm, given in both metric and imperial, is a specific and checkable claim, and most pinless meters say nothing at all about how far they see.
Now the consequence that listings almost never explain. The reading is the response of the whole volume inside the field, not a measurement at a plane 20 mm down. Everything within reach contributes, weighted toward the surface because the field is strongest there.
That means several very different conditions can produce similar numbers:
- A wet surface over a dry substrate.
- A dry surface over a wet substrate, reading lower than it should because the wet part is at the weak end of the field.
- A thin, very wet layer and a thicker, mildly damp one.
So depth of penetration is a double edged specification. It is what lets you find water behind a finish you are not allowed to damage, and it is what prevents you from saying where in the depth the water is. The method that resolves it is sequential: survey non invasively to find the area, then use pins, or a drilled hole with a relative humidity probe, to establish the depth and the actual moisture condition. A non invasive meter locates. It does not conclude.
The field also spreads sideways, not only inward, which is why a reading shifts as you approach a corner, an edge, a stud or a buried pipe. Keep the head flat and away from edges, and note where the construction changes.
Concrete and fiberglass are the hard cases for a pinless head
The last bullet claims wood, drywall, concrete and fiberglass. The breadth is a genuine strength of the measuring principle, and the two materials at the end of that list are the two where a dielectric reading is most easily misled, so they are worth taking apart.
Anything dense, conductive or metallic inside the field raises the response whether or not there is water present. In practice that means reinforcement bar and welded mesh in a slab, metal studs and track behind plasterboard, foil backed insulated board, salts in old plaster from previous water movement, and the fixings and staples holding a finish on. All of them read as wet.
Concrete brings a second problem of its own. It is hygroscopic and holds water deep in its thickness, so a surface reading is a poor guide to whether a slab is dry enough to take a floor covering. That decision is made with an in situ relative humidity probe set into a drilled hole and allowed to equilibrate, not with any surface instrument. A pinless meter is the right tool for finding where a slab is wettest and the wrong tool for signing off a floor.
Fiberglass insulation fails in the opposite direction. It is mostly air, so the field passes through with little to respond to, and readings stay low even when the material is holding significant water. A low number in a glass wool filled cavity is not evidence of a dry cavity.
None of this makes the claim false. It means a reading on these materials is only meaningful against a dry reference on the same construction, and that knowing what is behind the surface is part of using the instrument. Our explainer on why readings vary by material covers the rest of the cases.
A field calibration check is what makes a reading defensible
The third bullet describes automatic calibration checks along with user field calibration, and this is the feature most buyers will undervalue.
Almost no moisture meter offers any way to confirm it is working. You switch it on, it shows a number, and you decide to believe it. There is no obvious symptom when a head has drifted or taken a knock, because a wrong reading looks exactly like a right one.
Where that matters is in work where the reading is evidence. Flood and fire restoration, insurance disputes, dilapidation surveys, pre purchase inspections: in all of those someone may eventually ask how you know a building was dry, or wet, on a particular visit. A meter that was checked against its reference at the start of the survey, with readings logged from it automatically, supports an answer. A number written on a pad does not.
The logging is the other half of the same argument. Time and date stamped readings sent to an app, viewable and exportable, is what turns a survey into a drying record. Restoration work is a sequence: the same defined points, read repeatedly over days or weeks, showing that the trend is downward. That evidence lives or dies on whether the same locations were read each time and whether the dates are reliable, and doing it by hand is where survey data gets lost.
What the listing does not say is how the calibration check is performed, whether a reference block or standard comes with it, the export format, whether readings can be attached to named locations or a plan, how many the instrument holds on its own, and the Bluetooth range. The first and the fourth of those are the ones worth asking about.
Three times longer than an unstated figure
One claim in these bullets has no number behind it: operates up to three times longer than previous models. Three times an unpublished figure is not a figure, and battery life is not a trivial specification on a survey instrument. A meter that dies in a loft, a crawl space or the far corner of a flooded building costs a return visit, and the battery type decides whether you can rescue the day from a corner shop or not. Neither the hours nor the cell type is given.
A related pattern sits in the same bullet set: rugged housing to withstand tough job site conditions, with no ingress protection rating anywhere. On an instrument sold for flood restoration, where standing water is the working environment, an IP figure would not be a luxury.
| Item | Listing statement |
|---|---|
| Measurement method | Non invasive, no damage to the surface |
| Depth | Up to 20 mm, stated as three quarters of an inch |
| Connectivity | Bluetooth to the Protimeter Connect app |
| Logging | Readings with time and date stamps, viewable and exportable |
| Calibration | Automatic checks plus user field calibration |
| Display | Backlit LCD |
| Housing | Described as rugged, no rating given |
| Materials claimed | Wood, drywall, concrete, fiberglass |
| Battery life | Three times a previous model, no absolute figure |
| Scale and units of the reading | Not stated in the listing bullets |
| Measuring range | Not stated in the listing bullets |
| Accuracy or tolerance | Not stated in the listing bullets |
| Resolution | Not stated in the listing bullets |
| Battery type | Not stated in the listing bullets |
| Ingress protection rating | Not stated in the listing bullets |
| Measuring area of the head | Not stated in the listing bullets |
| Operating temperature and humidity range | Not stated in the listing bullets |
| Bluetooth range | Not stated in the listing bullets |
| Readings stored on the instrument | Not stated in the listing bullets |
| Export format | Not stated in the listing bullets |
The backlit display earns a plain word of credit, because the places a moisture meter is used are crawl spaces, roof voids, cupboards under stairs and rooms with the power off, and an unlit screen is unreadable in all of them.
Who needs this, and who needs pins instead
This suits building surveyors, flood and fire restoration technicians, flooring contractors and home inspectors. The job in all four cases is the same: find and map where moisture is, without marking a client’s decoration, and produce a dated record of having done it. Non invasive measurement, automatic logging and a calibration check are three features that reinforce each other into a coherent survey instrument, which is more than the sum of the bullets suggests.
Look elsewhere in three cases. If you need a moisture content percentage to make a decision, which includes anyone judging whether timber is dry enough to work, finish or install, that is a pin meter with a species correction and nothing else will do. If you are deciding whether a concrete slab is ready for a covering, that needs an in situ relative humidity probe rather than any surface reading, however deep. And if you expect the display to mean the same thing on glass wool as on plasterboard, the measuring principle will disappoint you.
The clean way to hold it in your head is this. Use it to find the wet area and to show, with dates, that the area is drying. Use something else to say how wet it actually is.
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Frequently Asked Questions
Why does a pinless meter not give a moisture content percentage?
Because of what it measures. The head generates a radio frequency electric field that penetrates the material, and the instrument reads the dielectric response of everything inside that field. Water has a much higher dielectric constant than dry timber, plaster or concrete, so more water gives a larger response. But the instrument does not know the composition, density or thickness of what it is looking at, so it cannot convert the response into a mass fraction. A pin meter can be related to timber moisture content because it measures between two known points in one material, with a species correction.
How should I use an instrument with no published scale?
Comparatively, which is how a pinless meter should be used regardless of what its display says. Find an area of the same material and construction that you are confident is dry, take a reading there, and treat that as your reference. Then survey outward and look for where the number rises. The pattern of the rise is the finding. A single reading in isolation from one of these instruments does not support a conclusion, whatever the number on the screen.
Is the 20 mm depth a good thing or a limitation?
Both, and the two are inseparable. The depth is what lets you find water behind a finish without drilling it, which is the entire reason to own the instrument. It is also why the reading is an average through that depth rather than a measurement at a point: a wet surface over a dry substrate and a dry surface over a wet substrate can produce similar numbers. A non invasive survey locates the area. Pins or a drilled hole with a hygrometer establish where in the depth the water actually is.
Why are concrete and fiberglass the difficult materials?
Because a dielectric reading responds to anything dense or conductive in the field, not only to water. Reinforcement bar and mesh in concrete, metal studs, foil backed plasterboard and salts in old plaster all raise the response with no extra water present. Fiberglass insulation has the opposite problem: it is mostly air, so the field passes through largely unimpeded and the reading stays low even when the material is holding water. The claim that it works on these materials is true, and on both of them a dry reference reading on the same construction is not optional.
What is three times longer than previous models worth?
Not much as published, because three times an unstated figure is not a figure. Battery life matters on a survey, since a meter that dies in a loft or under a floor costs a return visit, and battery type matters at least as much: a cell you can buy in any shop is a different proposition from a proprietary pack. Neither the hours nor the type is given. It is the one claim in these bullets with no number attached to it.
Why does a calibration check matter on a moisture meter?
Because most moisture meters give you no way to know whether they are working. A reading is a number from a box you are choosing to trust. This instrument is described as having automatic calibration checks plus a user field calibration, and the value shows up in restoration and survey work, where a reading is evidence in a dispute about whether a building was dry. A meter verified at the start of a survey, with time stamped readings logged from it, carries weight that a bare number on a notepad does not.
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