Humidity calibration from 10 to 90 %rh
UKAS-accredited calibration for hygrometers, humidity transmitters, combined temperature and humidity probes and dew point sensors, carried out in environmental chambers in Lymington by Labcal, the Gill Group's calibration laboratory.
What is humidity calibration?
Humidity calibration places an instrument in an environmental chamber held at a known, stable relative humidity and compares its reading with a traceable reference. The certificate records the humidity error and uncertainty at each point, which is what cleanroom, storage and GMP monitoring records depend on.
Unlike pressure or temperature, relative humidity cannot be applied directly to a sensor, so the whole instrument has to sit in a controlled atmosphere. Labcal's chambers also calibrate the temperature probes built into humidity instruments, and dew point sensors are accredited from -15 °C to 40 °C.
Relative humidity, dew point and the temperature beside them
The humidity range depends on chamber temperature, and the uncertainty depends on probe length, so tell us the instrument and the conditions it works in.
| Instrument or quantity | Range | Expanded uncertainty (k=2) |
|---|---|---|
| Relative humidity, at 15 to 40 °C | 10 to 90 %rh | 1.5 %rh |
| Relative humidity, at 10 to 15 °C | 15 to 90 %rh | 1.5 %rh |
| Temperature probes built into humidity meters | -5 to 10 °C | 0.22 °C |
| Temperature probes built into humidity meters | 10 to 40 °C | 0.15 °C |
| Dew point | -15 to 0 °C | 0.35 °C |
| Dew point | 0 to 20 °C | 0.18 °C |
| Dew point | 20 to 40 °C | 0.21 °C |
Ranges and best measurement capability from the UKAS schedule of accreditation for laboratory 0625, issue 055, 18 August 2026. Q[a, b] means the two terms are combined in quadrature. The uncertainty on your certificate depends on the instrument under test.
The instruments that guard storage, cleanrooms and processes
Hygrometers
Handheld and fixed hygrometers used for spot checks and environmental monitoring.
Humidity transmitters
Transmitters feeding building management, cleanroom and process control systems.
Combined temperature and humidity probes
Probes calibrated for relative humidity and for the temperature sensor built into them.
Dew point sensors
Dew point instruments, accredited from -15 °C to 40 °C dew point.
Environmental data loggers
Loggers used to record storage, transport and laboratory conditions.
Humidity controllers
Relative humidity controllers and indicators, calibrated with their sensor where possible.
Typical makes include Fluke, HygroPalm, Michell Instruments, Rotronic, RS, RS PRO, Testo, TSI and Vaisala.
From your bench to a certificate and back
Tell us what needs calibrating
Use the form on this page with the instrument, the quantity and the points you need. If you are moving from another laboratory, your current certificate is enough for a like-for-like quote, usually within 24 hours.
Send it to Lymington
Instruments come to the Labcal laboratory at Ampress Park, Lymington. Calibration is laboratory based rather than on site. Courier collection can be arranged for regular and high-volume customers.
Calibration against traceable references
Turnaround averages 8 working days from the day the instrument arrives, with a 3-day fast track available by arrangement. Where an instrument can be adjusted, it is recorded as found, adjusted and recorded again as left.
Certificate and return
A UKAS certificate states the measured values, the expanded uncertainty at k=2 and the traceability to national standards, with as-found and as-left results where adjustment was made.
Request a quote
Tell us what needs calibrating
The instrument, how many and the points you need are enough to start. If you are switching laboratory, mention it and we will ask for your current certificate so the quote matches it like for like.
UKAS accredited. Labcal, laboratory 0625, ISO/IEC 17025:2017.
We aim to respond in one working day. Turnaround averages 8 working days from arrival, with a 3-day fast track by arrangement.
Switching laboratory? Send your current certificate for a like-for-like quote.
Frequently asked questions
Labcal's UKAS accreditation covers relative humidity from 10 %rh to 90 %rh at chamber temperatures of 15 °C to 40 °C, and from 15 %rh to 90 %rh at 10 °C to 15 °C, with an expanded uncertainty of 1.5 %rh. Dew point is accredited from -15 °C to 40 °C.
Humidity is calibrated in an environmental chamber because relative humidity cannot be applied to a sensor the way a pressure or a temperature can. The instrument has to be exposed to a stable, known atmosphere, and the reference instrument measures the same air, so both readings can be compared directly.
Yes. Labcal's UKAS schedule includes temperature probes built into humidity meters, from -5 °C to 40 °C, calibrated in the same environmental chamber. This is useful for combined probes where both readings feed environmental monitoring or GMP records, because both readings are then covered by the same certificate.
The calibration interval for a humidity instrument should be set by your quality system, based on how critical the measurement is, the accuracy needed and the sensor's drift at previous calibrations. Annual calibration is commonly adopted in pharmaceutical manufacturing and in cleanroom and HVAC monitoring.
Probe length can affect the achievable uncertainty, which is why Labcal's UKAS schedule states that the humidity and built-in temperature uncertainties depend on probe length. Tell us the probe dimensions when you ask for a quote so the laboratory can confirm what it can achieve.
Talk to an engineer
Tell us what you need to measure, where and under what conditions. We’ll help you work out the appropriate approach.