Extech Instruments RH490 User manual

User's Guide

Precision Hygro-Thermometer

Model RH490

RH490 V2.0 12/06

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.

Warranty

EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free

of defects in parts and workmanship for one year from date of shipment (a six

month limited warranty applies to sensors and cables). If it should become

necessary to return the instrument for service during or beyond the warranty

period, contact the Customer Service Department at (781) 890-7440 ext. 210 for

authorization or visit our website www.extech.com for contact information. A

Return Authorization (RA) number must be issued before any product is returned

to Extech. The sender is responsible for shipping charges, freight, insurance and

proper packaging to prevent damage in transit. This warranty does not apply to

defects resulting from action of the user such as misuse, improper wiring,

operation outside of specification, improper maintenance or repair, or

unauthorized modification. Extech specifically disclaims any implied warranties

or merchantability or fitness for a specific purpose and will not be liable for any

direct, indirect, incidental or consequential damages. Extech's total liability is

limited to repair or replacement of the product. The warranty set forth above is

inclusive and no other warranty, whether written or oral, is expressed or implied.

RH490 V2.0 12/06

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 V2.0 12/06

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).

RH490 V2.0 12/06

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.

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)

RH490 V2.0 12/06

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.

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.

RH490 V2.0 12/06



Support line (781) 890-7440

Technical support: Extension 200; E-mail: [email protected]m

Repair & Returns: Extension 210; E-mail: [email protected]

Product specifications subject to change without notice

For the latest version of this User’s Guide, Software updates, and other

up-to-the-minute product information, visit our website: www.extech.com

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

-22.0 to – 3.9oF

-30.0 to -19.9oC ±2.7oF

±1.5oC

-4.0 to 158.0oF

-20.0 to 70.0oC ±1.8oF

±1oC

Temperature

158.1 to 199.0oF

70.1 to 100.0oC ±2.7oF

±1.5oC

Wet Bulb 32 to 176°F (0 to 80°C)

Dew Point -22 to 199°F (-30 to 100°C)

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)

Calibration and Repair Services

Extech offers repair and calibration services for the products we sell. Extech

also provides NIST certification for most products. Call the Customer Service

Department for information on calibration services available for this product.

Extech recommends that annual calibrations be performed to verify meter

performance and accuracy.

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