What Is a Hygrometer and What Does It Measure?
A hygrometer is an instrument used to measure the relative humidity (RH) of air or gas.
Humidity measurement is a critical parameter in laboratories, cleanrooms, climatic chambers, and all environments where temperature and moisture must remain controlled.
Different technologies are used, depending on the application:
- Capacitive sensors – the most common, offering excellent accuracy and stability;
- Resistive sensors – ideal for fixed environmental conditions;
- Dew-point hygrometers – used to measure very low humidity levels.
Regardless of the technology, measurement reliability depends on periodic calibration and metrological traceability, in accordance with ISO 17025 standards.
Thermohygrometer: Two Measurements in One Device
A thermohygrometer measures both temperature and humidity, providing complete environmental data in a single instrument.
It is widely used in pharmaceutical facilities, laboratories, warehouses, and hospitals, where both parameters are vital for maintaining product integrity and process compliance.
Modern thermohygrometers often include a datalogger or digital interface that records measurements continuously, generating reports compliant with GLP (Good Laboratory Practice) and GMP (Good Manufacturing Practice).
How to Choose the Right Humidity Measurement Instrument
Selecting the proper hygrometer or thermohygrometer depends on:
- Measurement range – for example, 5%–95% RH;
- Accuracy – in cleanroom validation, uncertainty must be below ±2% RH;
- Environmental conditions – temperature, airflow, or vapor presence;
- Certifications – preference should be given to ISO 17025-calibrated instruments;
- Connectivity – integration with monitoring systems (e.g. SCADA).
An incorrect selection can lead to non-conformities, validation errors, or even product degradation in sensitive environments.
Calibration and Metrological Traceability
The calibration of hygrometers and thermohygrometers ensures that readings remain accurate and traceable to reference standards.
At the QSGroup laboratory, calibrations are performed on:
- digital and analog hygrometers;
- thermohygrographs and chain systems;
- temperature and humidity dataloggers;
- climate monitoring units.
Operating range: 5%–95% RH and -80°C to +500°C, with calibration performed under controlled thermo-hygrometric conditions.
Each instrument receives an Accredia Calibration Certificate, proving compliance with GMP, ISO, and FDA standards.
Why ISO 17025 Calibration Matters
An ISO 17025-accredited calibration ensures:
- Traceability to national and international standards;
- Accuracy and repeatability of humidity readings;
- Regulatory compliance for audits and validation;
- Reduction of process deviations and costs due to measurement errors.
Regular calibration is not just a quality control step—it’s a compliance requirement for regulated industries.
Conclusion
Whether it’s a standalone hygrometer or an integrated thermohygrometer, accuracy and compliance depend on reliable calibration.
QSGroup provides calibration, maintenance, and consulting services to ensure humidity measurements you can trust.
