Quick answer: The testo 174 H creates a time-stamped environmental record. The 174 T logs temperature; the 174 H additionally records relative humidity. Data quality depends on placement, programming and recovery of the whole recording.
What makes the testo 174 H different
The testo 174 H logs air temperature and relative humidity together; RH changes may reflect temperature changes even when absolute moisture is similar. Confirm the exact variant and its readout/software before following a setup menu. For related guidance, see testo 174-T: How to Configure and Interpret Temperature Logs.
Prepare and carry out the measurement
- Identify the exact logger variant and compatible readout method, then synchronize the clock and units.
- Select a sample interval and start condition matched to the expected event duration, memory and battery life.
- Mount where conditions represent the monitored product or space rather than the door or fan jet, and run a short functional check.
- Export the readings, document gaps/excursions and compare them with the site’s own limits and process context.
Model-specific use and interpretation
Set recording schedule and logging interval, deploy away from heat and moisture plumes, and record clock, location and sensor protection. Review temperature and RH trends together rather than isolating one high reading.
An air logger measures the local environment around its sensor, not automatically the product core temperature. Humidity peaks can arise from local temperature changes and access events. For broader instrument-selection criteria, see the temperature and humidity data logger selection guide.
Brief RH peaks during cleaning or access may need different interpretation from prolonged damp conditions. The sensor does not directly measure surface condensation or material moisture. For a separate assessment of surface-condensation risk, see the testo 625 condensation and mould risk guide.
Worked example (hypothetical)
Hypothetical plan: logging every five minutes for a seven-day period requires 7 × 24 × 12 = 2,016 timestamps per channel, before any additional setup or metadata records.
When measurements disagree
Choose logger position according to the risk: a unit at a doorway may see different peaks from a unit near the most vulnerable stored goods. Mark the measuring location in every export.
Compare humidity excursions and temperature together, because relative humidity changes with temperature; neither channel proves that packaged products were wetted or damaged.
- Check for direct sunlight, localized airflow or drafts at the logger position.
- Inspect the sensor opening and allow stabilization after moving the instrument.
- Compare only with a reference instrument that has suitable documented calibration for the tested environment.
- For sensitive goods or regulated storage, use the governing acceptance limits and record corrective action when excursions occur.
Interpret RH together with temperature
The 174 H logs both air temperature and relative humidity, so a humidity spike must be interpreted alongside temperature. Placement beside a door or wet-cleaning station can overstate conditions elsewhere. Define expected event duration before choosing the interval and check the logger’s clock during download. An environmental RH trace does not directly measure surface water or hidden mold.
Interpretation: A drop in air temperature can raise measured relative humidity even without the same increase in actual water-vapor mass; use both channels to evaluate the trend.
Limits and safety
Follow the exact instrument manual and the equipment manufacturer’s acceptance criteria. The example is not field evidence, a legal limit or a commissioning target. Work on energized electrical equipment, combustion systems, charged refrigerant circuits or hot surfaces requires qualified personnel and the site’s approved protective procedures.