Climate, Dewpoint & Relative Humidity
A dew point meter measures or calculates climatic parameters used to assess conditions around coating work. Relative humidity, air temperature, surface temperature, dew point temperature and Delta T are distinct values, not interchangeable readings. Results require assessment against the coating manufacturer’s instructions, project specification and approved procedure before application starts or continues.
Within our Coatings Inspection equipment, digital instruments sit alongside manual hygrometers, a calculator and contact, magnetic or infrared thermometers. They support electronic or wet- and dry-bulb methods while distinguishing atmospheric humidity from substrate moisture. A climatic reading represents its location and time; conditions may change across a structure or during work.
Why Use a Dew Point Meter Before Coating?
Condensation may form when a surface reaches or falls below the dew point under the measured atmospheric conditions. Applying a coating when condensation is present, or when the specified surface-to-dewpoint margin is not maintained, may affect application or subsequent coating behaviour. Measurements support comparison with stated limits.
Delta T is the difference between surface temperature and dewpoint temperature, not between air temperature and dewpoint. A surface-temperature margin of 3°C above dewpoint is commonly referenced, but it is not universal. The required margin and relative-humidity limit must come from the coating manufacturer, project specification, or method.
A dew point meter supports comparison with these criteria but does not independently approve application or guarantee coating performance. Preparation, application and other specified controls also matter.
What Climatic Parameters Can Be Measured?
Relative humidity expresses the water vapour present as a percentage of saturation at the same air temperature. Dewpoint is the temperature at which air becomes saturated under current conditions, and condensation may begin. Air temperature describes the atmosphere around the work; surface temperature describes the substrate at the measured position. Delta T compares surface temperature with dewpoint.
Depending on model and probe arrangement, equipment may also display dry-bulb temperature, wet-bulb temperature, specific humidity or external probe temperature. The Elcometer 319 Dewpoint Meter measures and records relative humidity, air temperature, surface temperature, dewpoint temperature and Delta T. As a digital hygrometer or thermo hygrometer, it combines air-temperature and relative-humidity functions with surface-temperature measurement and coating-specific calculations.
Model S stores ten records for manual review. Model T adds batch memory, automatic interval logging, and USB or Bluetooth transfer. Capabilities remain version-specific.
A manual Elcometer 116A whirling hygrometer or 116C sling hygrometer obtains wet- and dry-bulb readings used to determine relative humidity and dewpoint. The Elcometer 114 Dewpoint Calculator is a physical calculator, not a sensor. A separate surface thermometer supplies the temperature needed to calculate Delta T. A humidity meter for coating inspection assesses atmospheric relative humidity rather than moisture within a material.
Where Is Climate Measurement Used?
Climatic checks support protective-coating and industrial-finishing work on structural steel, marine assets, tanks, pipelines, bridges and fabricated components, plus maintenance projects and specified paint booths. Readings may be required before application and at intervals during work. Automatic logging supports longer monitoring when the model and procedure permit it.
Conditions vary with time, airflow, sunlight, shade, ventilation, enclosed spaces, and the temperatures of separate surface areas. One reading does not represent every location unless the inspection plan establishes otherwise.
Climate measurement is one coating control. Surface Profile concerns prepared texture, while Surface Cleanliness addresses residues such as dust and soluble salts. Dry Film Coating Thickness is assessed separately after application at the appropriate stage. None of these checks replaces another.
How to Choose Climate Inspection Equipment
Start with the parameters required by the project method. An integrated digital dew point meter displays several values directly, while a manual hygrometer arrangement separates wet- and dry-bulb readings, calculation and surface-temperature measurement. Compare range, stated accuracy, resolution, sensor response, operating conditions and required calibration or verification documentation.
Manual recording may suit occasional checks. Batch memory, timestamps, interval logging, alarms and USB or Bluetooth transfer matter when numerous readings or an electronic record are required. These functions remain model-specific.
Surface type and access influence thermometer selection. A magnetic thermometer needs a compatible magnetic substrate and suitable contact. A contact probe must seat correctly on the measured area. An infrared thermometer measures emitted infrared energy; its laser is only an aiming aid. Emissivity, target size and distance affect readings.
Sensor stabilisation, airflow, sunlight, radiant heat, rapid temperature changes, recent movement between environments, dirty sensors and unsuitable positions affect readings. Manual wet-bulb methods depend on correct wick condition, suitable water and proper operation. Selection should account for these controls without replacing the approved procedure.
Order a Dew Point Meter from Celtic Surveys
We supply equipment for dew point, relative-humidity, air-temperature and surface-temperature checks during coating inspection. An Elcometer dew point meter supports integrated digital measurement, while manual wet- and dry-bulb equipment and separate surface thermometers suit other approved methods. Data logging is available on selected models.
Selection should reflect the required parameters, measurement method, operating range, surface type, recording requirements, applicable procedure and calibration or verification needs.
Need help choosing a dew point meter for your work? Call 01 801 1335 or email sales@celticsurveys.ie for practical product advice before buying.