User's Manual

Official stations recalibrate or replace humidity sensors on a yearly basis.

Due to manufacturing tolerances, the humidity is accurate to ± 5%. To

improve this accuracy, the indoor and outdoor humidity can be calibrated

using an accurate source, such as a sling psychrometer:

http://www.ambientweather.com/mafaredspslp.html

or one step humidpak calibration kits (reference Section 8). You can also

use common table salt, water and a plastic bag:

http://ambientweather.wikispaces.com/ws23

Discussion: Temperature errors can occur when a sensor is placed

too close to a heat source (such as a building structure, the ground or

trees).

To calibrate temperature, we recommend a mercury or red spirit (fluid)

thermometer. Bi-metal (dial) and other digital thermometers are not a good

source and have their own margin of error. Using a local weather station in

your area is also a poor source due to changes in location, timing (airport

weather stations are only updated once per hour) and possible calibration

errors (many official weather stations are not properly installed and

calibrated).

Place the sensor in a shaded, controlled environment next to the fluid

thermometer, and allow the sensor to stabilize for 48 hours. Compare this

temperature to the fluid thermometer and adjust the console to match the

fluid thermometer.

5. Glossary of Term

Term

Definition

Accuracy

Hygrometer

Range

Accuracy is defined as the ability of a measurement to

match the actual value of the quantity being measured.

A hygrometer is a device that measures relative

humidity. Relative humidity is a term used to describe

the amount or percentage of water vapor that exists in air.

Range is defined as the amount or extent a value can be

measured.