Extech Instruments RH490-NIST User manual

User's Guide

Precision Hygro-Thermometer

Model RH490

RH490-EU-EN-V2.2-07/13

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

RH490-EU-EN-V2.2-07/13

Operation

Power

Press the power button “ “ to turn power on or off.

%RH

1. To select %RH measurement, press the “%RH/GPP/g/Kg” button.

2. Hold the probe in the area to be tested.

3. Allow adequate time for readings to stabilize.

4. The Relative Humidity measurement appears in the top display.

5. Pressing the “°F/°C/WBT/Dew Point” button toggles the lower

display between Temperature (°F), Temperature (°C), Dew Point

(°C), Dew Point (°F), Wet Bulb (°C) and Wet Bulb (°F).

Mixing Ratio (Grains Per Pound or Grams Per Kilograms)

1. To select GPP or g/kg measurement, press the “%RH/GPP/g/Kg”

button.

2. Hold the probe in the area to be tested.

3. Allow adequate time for readings to stabilize.

4. The GPP or g/Kg measurement appears in the top display.

5. Pressing the “°F/°C/WBT/Dew Point” button toggles the lower

display between Temperature (°F), Temperature (°C), Dew Point

(°C), Dew Point (°F), Wet Bulb (°C) and Wet Bulb (°F).

Dew Point

1. To select the Dew Point measurement, press the “°F/°C/WBT/Dew

Point” button until DEWPOINT (°F or °C) appears in the lower

right.

2. Dew Point temperature is now displayed.

Wet Bulb

1. To select the Wet Bulb measurement, press the “°F/°C/WBT/Dew

Point” button until WET BULB

(°F or °C) appears in the lower right.

2. Wet Bulb temperature is now displayed.

RH490-EU-EN-V2.2-07/13

Temperature

1. To select the temperature measurement, press the

“°F/°C/WBT/Dew Point” button until “°C” or “°F” appears in the

lower right.

2. Temperature is now displayed.

Data Hold

1. Press the ”H MAX MIN” button momentarily to freeze the displayed

readings. ”HOLD” will appear on the upper left-hand side of the

display.

2. Press the ”H MAX MIN” button three more times to return to normal

operation. (Steps through MAX and MIN)

Minimum (MIN) Maximum (MAX) Function

The MIN/MAX mode allows the user to view only the lowest (MIN) or highest (MAX) readings.

1. Press the ”H MAX MIN” button twice and “MIN” appears on the display. The LCD is now

displaying the minimum value recorded in both the top and bottom display. The display will not

change until a lower reading is registered.

2. Press the ”H MAX MIN” button again and “MAX” appears on the

display. The LCD is now displaying the maximum value recorded

in both the top and bottom display. The display will not change

until a higher reading is registered.

3. To exit the MIN/MAX mode, press the ”H MAX MIN” button again.

The “MAX” icon will disappear.

Note: Max and Min values are recorded into memory while the meter is

on. The values are erased when power is turned off.

Backlight

Press and hold the light button “ “ until the backlight turns on. To turn the backlight off, press and

hold the light button “ until the backlight turns off.

Automatic Power OFF

The meter has a default setting that automatically shuts the meter off after 10 minutes (indicated by

the symbol on the display).

This battery saving feature can be disabled.

To disable the auto power off function, press and hold the ”H MAX MIN” hold button while powering

on. The symbol will not appear when auto power off has been disabled.

The meter will revert to the default auto-off mode when powered off.

RH490-EU-EN-V2.2-07/13

Maintenance

Cleaning and storage

1. The meter should be cleaned with a damp cloth and mild detergent when necessary. Do not use

solvents or abrasives.

2. Store the meter in an area with moderate temperature and humidity (refer to the operating and

storage range in the specifications chart earlier in this manual).

Battery Replacement

When the battery becomes weak the “ “ battery symbol will appear on the LCD. Replace the 9

Volt battery by removing the Philips head screw holding the rear battery compartment cover to

access the battery compartment. Ensure that the compartment cover is securely fastened when

finished.

You, as the end user, are legally bound (Battery ordinance) to return all used batteries

and accumulators; disposal in the household garbage is prohibited!

You can hand over your used batteries / accumulators at collection points in your

community or wherever batteries / accumulators are sold!

Disposal: Follow the valid legal stipulations in respect of the disposal of the device at the

end of its lifecycle

Specifications

Function Range and Resolution Accuracy

0.0 to 10.0%RH ±3%RH

10.0 to 90.0%RH ±2%RH

Humidity

90.0 to 100.0%RH ±3%RH

-30.0 to -20.0oC

-22.0 to – 4.0oF

±1.5oC

±2.7oF

-19.9 to 70.0oC

-3.9 to 158.0oF

±1oC

±1.8oF

Temperature

70.1 to 100.0oC

158.1 to 199.0oF

±1.5oC

±2.7oF

Wet Bulb 0 to 80°C (32 to 176°F)

Dew Point -30 to 100°C (-22 to 199°F)

Mixing Ratio 0 to 1120 GPP (grains per pound)

0 to 160 g/kg (grams per kilogram)

Calculated from RH and air

temperature measurements

Display Dual LCD

Response Time: <30 seconds (90% of final value in moving air)

Operating Conditions 32 to 122oF (0 to 50oC); < 80% RH non-condensing

Storage Conditions -40 to 185oF (-40 to 85oC); <99% RH non-condensing

Power Supply 9 Volt battery

Battery Life Approx. 24 hours

Dimensions / Weight 7.8 x 1.7 x 1.3” (200 x 45 x 33mm); 7 oz. (200g)

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