The Humidity Laboratory provides metrological infrastructure for high-accuracy measurements of water content in gases and solid materials. Measurements are traceable to the International Temperature Scale ITS-90.
Overview
Humidity measurements in gases (and air) and moisture measurements in solid materials are important in many fields, including ensuring human health and comfort, energy, food, pharmaceuticals, battery and electronics manufacturing, weather and climate.
The main purpose of the humidity laboratory is to establish, maintain and disseminate the infrastructure for measuring humidity and moisture quantities – primarily relative humidity of air, absolute humidity, dew-point and frost-point temperatures, partial pressure, fraction and ratio of water vapor, water content in various gases, and water content in solid and powdery materials (including volatile components) – traceably to SI units and/or relevant standards.
In addition, traceable measurement of air temperature according to ITS-90 (International Temperature Scale-1990) is also within the scope of this laboratory. Accurate measurement of air temperature is of great importance in relative humidity measurements.
Research
High-accuracy measurement and calibration of relative humidity content in gases and air.
Determination of dew and frost point temperatures using reference measurement systems. Measurement of partial pressure, fraction and ratio of water vapor.
Temperature measurements traceable to the ITS-90 international temperature scale. Precise measurements are performed in the range -10 °C to 90 °C.
Determination of water content in solid and powdery materials using metrological methods. All fractions including volatile components can be measured.
High-accuracy measurement of water content in various gases and traceable calibration services.
Accurate determination of absolute humidity of air using SI-traceable methods.
Equipment
Currently, traceable calibrations of various indicating and non-indicating (software-linked) hygrometers, humidity sensors, humidity and temperature data loggers and transmitters, dew-point hygrometers, ambient condition recorders, and air temperature thermometers are performed in SI units.
Various indicating and non-indicating (software-linked) hygrometers. These are the primary reference instruments used in relative humidity measurement.
Humidity sensors based on different technologies and principles. Capacitive, resistive, and thermal conductivity principle sensors.
Chilled-mirror type instruments and electronic sensors measuring dew and frost point temperatures with high precision.
Devices that continuously record and transmit humidity and temperature data. Used for remote monitoring and data transfer.
Precision thermometers traceable to the ITS-90 scale. Temperature measurement instruments of critical importance in relative humidity measurements.
Infrastructure
| No | Equipment / System | Brand | Model | Range / Capacity | Purpose / Use |
|---|---|---|---|---|---|
| 1 | Dew-Point Generator (Two-Temperature) | Thunder Scientific | Model 2500 | 10–95 %rh / −10–80 °C | Primary humidity reference; calibration environment |
| 2 | Dew-Point Hygrometer (Reference) | MBW / Michell | DP30 / Optidew Vision | −40 °C – 80 °C dew point | Primary traceable reference meter |
| 3 | Capacitive Humidity Sensor (Reference Set) | Vaisala | HMT337 / HMP155 | 0–100 %rh, −40–80 °C | Transfer standard; calibration comparison measurements |
| 4 | Humidity Chamber (Seismically Isolated) | ERTCO / In-house | Custom | 5–98 %rh, 0–70 °C | Stable humidity calibration environment |
| 5 | Standard Platinum Resistance Thermometer (SPRT) | Isothermal Technology / Hart | Hyper Cal / 5681 | −80 °C – 660 °C | ITS-90 traceable air temperature reference |
| 6 | Data Acquisition System (DAQ) | Agilent / Keysight | 34970A / 34980A | Multi-channel analog input | Automatic temperature and humidity data recording |
| 7 | Fixed-Point Cell (Water Triple Point) | TuBiTak UME | WTP Cell | 0.01 °C (273.16 K) | ITS-90 primary temperature calibration reference |
Accuracy
Currently, the uncertainty of air temperature measurements in the laboratory has been reduced to 0.07 °C in the -10 °C to 70 °C range and 0.2 °C in the 70 °C to 90 °C range (k=2), and work is ongoing to further reduce these uncertainties.
| Temperature Range | Expanded Uncertainty (U) | Confidence Level |
|---|---|---|
| -10 °C – 70 °C | 0.07 °C | k=2 (approximately 95% confidence interval) |
| 70 °C – 90 °C | 0.2 °C | k=2 (approximately 95% confidence interval) |
* Uncertainty values are calculated using a coverage factor k=2 and correspond to an approximately 95% confidence interval.
Calibration
Traceable calibration of relative humidity and dew point measuring instruments. Calibration certificates are issued for hygrometers, humidity sensors and dew point thermometers.
Calibration of air temperature measuring instruments traceable to ITS-90. Performed with reference systems in the range -10 °C to 90 °C.
Measurement of moisture content in wood chips, paper, soil and similar samples. Determination of all fractions including volatile components.
Traceable calibration of humidity and temperature data loggers and transmitters in SI units. Calibration available both in the field and in the laboratory.
Services
Traceable humidity and temperature calibration to SI units and international standards.
Humidity and temperature measurements for ambient conditions, industrial processes and product quality.
Training services on humidity measurements, uncertainty calculations and international standards.
Technical support and collaboration for research and development projects in the field of humidity metrology.
Expert technical advice on measurement uncertainty, instrument selection and calibration methodology.
Joint measurement comparisons with national metrology institutes and assurance of the traceability chain.
Application Areas
The Humidity Laboratory provides calibration, measurement and consultancy services to institutions and organizations in the following sectors.