Is your hygrometer reading inaccurate? Reasons for inaccurate or incorrect readings and how to check them.

High humidity / Low humidity

First, please confirm the measurement location and measurement conditions.

Even within the same room, temperature and humidity can vary depending on the location. Also, if the hygrometer has just been moved from another location, it may not yet be accustomed to its surroundings.

If there are no problems with those, we will check for dew condensation and the condition of the sensors.

The two hygrometers show different readings.

Just because two hygrometers show different readings doesn't mean one of them is necessarily malfunction.

Please check the measurement location, the time elapsed since measurement began, the sensor's responsiveness, the measurement method, and the accuracy.

Humidity values fluctuate

If display value fluctuates, check not only the hygrometer but also the environment in which the measurement is being taken.

Actual humidity levels may fluctuate due to factors such as air conditioning and airflow. Additionally, static electricity, electromagnetic waves, and electrical noise may also affect the humidity levels depending on the equipment used.

Suddenly showing abnormal values

If a hygrometer that was previously functioning normally suddenly starts showing abnormal readings, please check if the measurement environment has changed recently.

In particular, check for dew condensation and any sudden environmental changes. If dew condensation is suspected, first thoroughly dry the sensor and then recheck.

The value doesn't change / display is incorrect.

Some handheld hygrometers have a HOLD function that holds the measured value. If the value does not change, first check if such a function is enabled.

Error display and output abnormalities can have different causes depending on the product, so please check the instruction manual for the model you are using.

Differences depending on the measurement location

Humidity is not always uniform, even within the same space.

Temperature and humidity distributions can vary depending on the location due to factors such as air conditioning, outside air, heat sources, and airflow.

Therefore, it is not possible to judge the accuracy of the equipment solely by comparing the readings of two hygrometers installed in different locations.

Time to adapt to the measurement environment

Immediately after moving a hygrometer to a different location, it's important not to rely solely on display value.

temperature/humidity hygrometers may need time to adjust to the surrounding environment. CHINO 's HN-EK series lists "not having adjusted to the surrounding environment" as a possible cause of unusually large errors, and advises users to observe the device for several hours.

dew condensation

If dew condensation the humidity sensor, it will no longer be able to measure accurately.

If dew condensation is suspected, do not continue the measurement and allow the product to dry completely according to the product's instruction manual.

Differences in hygrometers and measurement methods to compare

It's easy to assume that the readings will be the same if they're in the same location, but when comparing hygrometers, you need to be aware of differences in measurement methods.

The instruction manual for CHINO temperature/humidity explains that Assmann wet-bulb hygrometers and sensor-type temperature/humidity differ in how they capture air and their response. In environments with a distribution of temperature/humidity, indicated value may differ due to these differences.

When comparing hygrometers, please check at least the following conditions.

• Place them in the same measurement position as much as possible.
• Allow sufficient time after starting the measurement.
• Set the conditions, such as airflow.
• Confirm the measurement method and responsiveness.
• Check the respective accuracy ratings.

Airflow and noise

If the hygrometer reading is fluctuating, check the air quality being measured and the electrical environment.

For example, stable representative values may not be obtainable at air conditioning vents or in areas with strong airflow.

Additionally, for handheld devices, static electricity, electromagnetic waves, and high-frequency noise are also important to check, while for stationary devices, noise from power lines and other sources is also a key factor.

Contamination and deterioration during collection

Because humidity sensors measure humidity while being exposed to the surrounding atmosphere, their performance may degrade depending on the operating environment.

CHINO temperature/humidity include warnings regarding ketone-based and ester-based organic solvents, halogens, strong acids, corrosive substances, oil mist, salt mist, steam, chemicals, seawater, etc., depending on the model.

Furthermore, the storage environment also needs to be checked. If the hygrometer reading is inaccurate after not being used for a long period, check not only the usage history but also where it was stored.

dew condensation can prevent accurate measurements.

If dew condensation forms on the humidity sensor, causing water droplets to adhere, accurate humidity measurement is not possible.

First, let it dry completely.

If dew condensation is suspected, thoroughly dry the sensor. Some CHINO temperature/humidity recommend ventilating the element and allowing it to dry completely for about half a day.

If it doesn't return to normal after drying, suspect a sensor malfunction.

After drying thoroughly, if the readings return to normal when compared under the same conditions as a normal hygrometer, it may be possible to reuse it.

On the other hand, if the abnormal condition persists even after thorough drying, it is possible that the sensor has deteriorated or malfunction.

Correcting without checking the cause.

It's not recommended to immediately calibrate your hygrometer just because it reads differently from another one.

If the difference in values is due to factors such as the measurement location, environmental adaptation, dew condensation, responsiveness, and temperature/humidity distribution, correcting for these factors will not resolve the cause.

Furthermore, the mechanism of the correction function varies depending on the product. For example, the output correction of the HN-EKA□N is zero-point shift, and if the output of 50%rh is corrected to 53%rh, a 3%rh correction will also be applied even if the output is 0%rh.

Continue using it while dew condensation is present.

Accurate measurements cannot be taken when dew condensation. Do not continue measuring if abnormal values are being displayed; instead, follow the product's instruction manual to allow it to dry and return to normal operation.

Replace the sensor without checking the cause.

Replacing the sensor may resolve the issue, but if the cause lies in the measurement location, airflow, comparison conditions, dew condensation, etc., the same problem may occur even after replacing the sensor.

First, we check the measurement conditions, and based on the results, we determine whether the sensor needs to be replaced.

Suspect sensor degradation or malfunction.

Humidity sensors have a limited lifespan. However, this lifespan varies greatly depending on the operating environment, so it cannot be judged solely by the number of years.

Some products have recommended replacement intervals. For example, the HN-EKA□N model has a recommended replacement interval for the sensor unit of one year. On the other hand, the HN-EH series indicates that the sensor has a limited lifespan and advises replacement when symptoms occur.

Please refer to the product's instruction manual and consider the actual usage environment and symptoms to make a judgment.

Consider calibration or inspection.

When the accuracy of measurements is crucial for quality control or equipment management, simply matching the readings of another hygrometer is not sufficient to determine that the required precision is being met.

If accuracy needs to be verified, consider comparing it to a calibrated reference standard or performing calibration yourself.

Things to tell CHINO when you consult with him

If you are unable to identify the cause yourself, you can consult the manufacturer instead of attempting to correct the problem or replace the sensor yourself.

When seeking advice, organizing the following information to the best of your knowledge will provide clues to understanding the situation.

• Product name/model
• serial number
• What are the symptoms?
• Current display value / output value
• When did the symptoms start?
• The range of temperature and humidity being used
• Location where installation and measurement are being performed
• Presence or absence of dew condensation
• Presence of chemicals, organic solvents, etc.
• Conditions and results when compared with other hygrometers