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Extech · Extech MO290 Pinless Moisture Psychrometer with IR Thermometer
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Verdict
The Extech MO290 is built for the person who has to explain where moisture is coming from, not just that it exists. A pinless sensor finds elevated moisture in a wall or floor, the remote pin probe confirms it by contact, the humidity and air temperature sensor gives the dew point, and the infrared thermometer reads the surface temperature so the meter can tell you whether condensation is likely at that spot. That is a complete condensation diagnosis in one hand. Its limits are the ones every combination instrument has: each sensor is competent rather than best in class, and the infrared reading is a single spot with a fixed emissivity. For restoration contractors, home inspectors and property managers who chase damp complaints, the documentation supports it as a practical field tool.
Who It Is For
- Restoration and drying contractors who need moisture content and psychrometric data on the same visit.
- Home inspectors and surveyors who want to distinguish condensation from a leak.
- Property managers investigating recurring damp or mould complaints.
Someone who only needs to know whether drywall is wet will be served by a simpler pinless meter. Our guide to choosing a moisture meter explains when the extra functions are worth having.
Documented Specifications
| Item | Documentation |
|---|---|
| Pinless moisture sensor | Measures to 0.75 inch below the surface |
| Pin probe | Remote pin-type probe on a 3 foot cable for contact readings |
| Air measurements | Air temperature and relative humidity |
| Infrared thermometer | Non-contact, 8:1 distance-to-spot ratio, fixed 0.95 emissivity |
| Calculations | Dew point and differential temperature to indicate condensation point |
| Alarms | Programmable high and low moisture and humidity alarms |
| Display | Large dual display with backlight |
How the Functions Work Together
Damp on an internal wall has two common causes: water getting in, or warm humid air condensing on a cold surface. A moisture meter alone cannot tell them apart. The MO290 approaches the question in three steps. The pinless sensor is swept over the wall to locate the wet area. The humidity and air temperature reading is used to calculate the dew point of the room air. The infrared thermometer is then pointed at the wet patch to read its surface temperature. If the surface is at or below the dew point, condensation is the likely mechanism; if the surface is warm and still wet, the water is arriving some other way. The manufacturer describes this differential temperature calculation as automatic, so the meter reports the margin rather than leaving you to do the arithmetic. Our article on using thermal imaging to look for moisture problems covers the same logic for a camera-based survey.
Pinless Sensor and Pin Probe
The pinless sensor is the scanning tool. It reads through paint, wallpaper and tile to about 0.75 inch without marking the surface, which suits finished interiors. Pinless readings are influenced by density and by anything metallic or wet behind the surface, so a high reading is a reason to look closer rather than a conclusion. The remote pin probe answers that. Pushed into drywall or wood, it gives a contact reading at the pin depth that is far less affected by what lies behind. The 3 foot cable also lets the probe reach into cavities, under sinks and behind appliances while the display stays readable. See pin versus pinless moisture meters for the trade-offs in more depth.
Infrared Thermometer Notes
The 8:1 distance-to-spot ratio means that at 8 inches the meter averages a spot roughly 1 inch across; at 4 feet the spot is about 6 inches. For a surface temperature reading you should be close. The fixed 0.95 emissivity is appropriate for painted plaster, drywall, wood and most building materials, which are the surfaces this meter is designed for. It will read low on bare metal or glossy surfaces, and there is no emissivity adjustment to correct that. Our guide on setting emissivity explains why.
Strengths
- Moisture content, air conditions and surface temperature from one instrument.
- Automatic condensation-risk calculation removes a common source of error in damp diagnosis.
- Both pinless scanning and a remote pin probe are included.
- Programmable alarms allow hands-free sweeping of a wall.
Limitations
- Fixed emissivity limits the infrared thermometer to non-metallic surfaces.
- Pinless depth of 0.75 inch is shallower than deep-scanning meters such as the MO57A.
- More functions mean more menu navigation than a single-purpose meter.
How It Compares
The Extech MO265 offers the same pinless-plus-pin combination without the psychrometric and infrared functions, at a lower price. The MO257 is pinless only and simpler still. The MO280 adds wood-species selection for people who mainly test timber. The MO290 is the choice when condensation diagnosis, rather than moisture content alone, is the recurring job.
How We Research
This review is based on the manufacturer’s published specifications, the Amazon product listing and patterns in owner reports. We did not run laboratory tests. Background reading: how to measure relative humidity correctly.
Recommended Tools
Products shown because their documented specifications fit this guide. Price and availability are on Amazon and can change.
Frequently Asked Questions
What is a moisture psychrometer?
A psychrometer measures air temperature and relative humidity so that dew point can be calculated. The MO290 adds that function to a moisture meter, so one instrument can tell you both how wet a material is and whether the air around it is likely to condense on cold surfaces.
Does the MO290 use pins or a pinless sensor?
Both. The built-in sensor is pinless and reads to about 0.75 inch below the surface. A remote pin probe on a 3 foot cable is included for contact readings and for confirming a pinless result.
What is the infrared thermometer for?
It reads surface temperature without contact at an 8:1 distance-to-spot ratio with a fixed emissivity of 0.95. The meter compares that surface temperature with the calculated dew point to indicate condensation risk.
Is it a substitute for a thermal camera?
No. The infrared thermometer reads one spot at a time. It is useful for checking a suspect area found by a thermal camera or by the moisture sensor, not for scanning a whole wall.
Affiliate disclosure: Akermin earns a commission from qualifying Amazon purchases made through links on this page. Our editorial picks are based on documented specifications and owner feedback, not commissions.
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