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RH490-EU-EN-V2.2-07/13
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Introduction
Congratulations on your purchase of the Extech RH490 Precision Hygro-Thermometer. This device
measures Humidity, Air Temperature, Dew Point temperature, Wet Bulb temperature and Grains of
Water Vapor per Pound of Air. Advanced features include Data Hold, Auto Power Off, and MAX/MIN
reading. This meter is shipped fully tested and calibrated and with proper use will provide years of
reliable service.
Meter Description
1. Humidity & Temperature Sensor
2. LCD Display
3. Power ON/OFF button
4. °F/°C/WBT (wet bulb)/Dew Point button
5. Hold/MIN-MAX button
6. %RH, GPP, g/Kg, Backlight button
Note: The battery compartment is located
on the rear of the instrument
Display Description
1. Relative Humidity %
2. Dew Point
3. Wet Bulb
4. °C/°F
5. Temp/WB/DP Display
6. Maximum
7. Minimum
8. Low Battery
9. Hold
10. RH% Display
11. Auto Off
12. Grains per pound
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3
6
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