Extech Instruments RH401 User manual

User's Guide

Digital Psychrometer + IR Thermometer

Models RH401 and RH405 (kit)

Introduction

Congratulations on your purchase of the Extech RH401 Digital Psychrometer + InfraRed

Thermometer. This device measures Humidity, Air Temperature, Dew Point and Wet Bulb.

Advanced features include Infrared Non-Contact Surface Temperature Measurement, Data

Hold and programmable Auto Power Off. The retractable probe protects the sensors when

the meter is not in use. Careful use of this meter will provide years of reliable service.

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RH401 V1.4 11/07

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Specifications

Function Range and Resolution Accuracy

Humidity 0.0 to 100.0% RH ±3% RH (10 to 90%)

Temperature (Air) -4.0 to 122.0oF (-20 to 50oC) ±1.8oF (±1oC)

-4 to 842oF (-20 to 450oC) ±3% reading or ±3oC/6oF

whichever is greater

Temperature (InfraRed)

(@25ºC ±5ºC) -40 to -4oF, 842 to 932oF

-40 to -20oC, 450 to 500oC ±4% reading or ±4oC/8oF

whichever is greater

Display Triple LCD with backlight

Sensor Type Humidity: Capacitance sensor; Temperature (air): Thermistor

Dew Point -90.4 to 122.0oF (-68 to 50oC) (calculated from humidity and

temperature measurements)

Wet Bulb -6.9 to 122.0oF (-21.6 to 50oC) (calculated from humidity and

temperature measurements)

IR Emissivity Adjustable from 0.3 to 0.99

IR Spot/Distance Ratio 8:1

IR Response Time 0.5 seconds

Operating Conditions -4 to 122oF (-20 to 50oC); < 99% RH non-condensing

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

Power Supply 4 x 1.5V ‘AAA’ batteries or AC adaptor

Battery Life approx. 150 hours (laser inactive); 30 hours (laser active)

Dimensions / Weight 6.8x2.7x1.9” (175x70x50mm); 4.9 oz. (140g)

Meter Description

1. Emissivity adjust indicator

2. Laser pointer on indicator

3. Low Battery indicator

4. IR Surface Temperature button

5. ON/OFF/Setup button

6. Back Light button

7. Laser/Down button

8. °F/°C/Up button

9. Dew Point/Wet Bulb button

10. % Humidity display

11. Air Temperature, Dew Point or Wet Bulb display

12. IR Surface Temperature display

13. Extended probe with Humidity &

Air Temperature Sensors

14. PC interface port

15. AC adaptor jack

Note: The battery compartment is located on the rear of the instrument

RH401 V1.4 11/07

Operation

Retractable Humidity and Air Temperature Sensor

Press down on the sensor, located at the top of the meter, to

release it. Humidity and air temperature will not be displayed if the

sensor is not extended.

After use, press the sensor into the stored (protected) position.

Power ON/OFF

Press the (or the button) to turn power on. The

meter will perform a short self-test when turned on.

Press and hold the button for three seconds to turn power off.

Humidity and Air Temperature measurements

1. Hold the meter in the area to be tested.

2. Allow adequate time for readings to stabilize.

3. View the Relative Humidity measurement in the lower display.

4. View the Air (probe)Temperature measurement in the middle display

Wet Bulb and Dew Point measurements

1. To display the Dew Point measurement, press and hold the button until the

symbol DP appears in the middle display.

2. Dew Point temperature is now displayed.

3. To display the Wet Bulb measurement, press and hold the button until the

symbol Wb appears in the middle display .

4. Wet Bulb temperature is now displayed.

5. To display IR temp –DP temp (IR surface temperature-Dew Point), press and hold the

button for more than 2 seconds then press the IR Temp button. The reading

can now be viewed in the top display.

6. Press and hold the button for more than 2 seconds to toggle the display back

to IR temperature.

Non-Contact InfraRed Surface Temperature measurements

1. Point the meter toward the surface to be measured.

2. Press and hold the button.

3. View the temperature measurement in the upper display

4. Release the nd the reading will be held on the display until a new reading is

taken.

5. While holding down the button, press the button to toggle the laser

targeting pointer on/off. The symbol will appear in the middle left of the display

indicating that surface temperature measurement is active and the laser pointer is on.

WARNING! The Laser button enables/disables the Laser pointer. When

enabled, each press of the button turns on the Laser beam. Avoid looking directly

into the path of the Laser or pointing the Laser toward anyone’s eyes. Mirrored surfaces

near a measurement object can redirect the Laser, use extreme caution. Do not allow

the Laser beam to be directed toward explosive gases.

Sensor

Extended

Stored

Sensor

Press Here

RH401 V1.4 11/07

IR Emissivity Adjustment

Emissivity is adjustable from 0.3 to 0.99. The default value is 0.95 which is the typical

emissivity value of many non-metallic surfaces. If the surface to be measured is highly

reflective and the emissivity is not known, cover the surface with paint or tape to improve

measurement accuracy. If the emissivity of the surface is known, follow this procedure to

set the value.

1. With the meter on, Press the key twice to enter the Emissivity setting procedure.

will flash on the top left side of the display.

2. Use the up key and the down key to adjust the value.

3. When the desired setting appears in the display, press again to save and return

back to normal operation.

Emissivity Factors for Common Materials

Material under test Emissivity Material under test Emissivity

Asphalt 0.90 to 0.98 Cloth (black) 0.98

Concrete 0.94 Skin (human) 0.98

Cement 0.96 Lather 0.75 to 0.80

Sand 0.90 Charcoal (powder) 0.96

Soil 0.92 to 0.96 Lacquer 0.80 to 0.95

Water 0.92 to 0.96 Lacquer (matt) 0.97

Ice 0.96 to 0.98 Rubber (black) 0.94

Snow 0.83 Plastic 0.85 to 0.95

Glass 0.90 to 0.95 Timber 0.90

Ceramic 0.90 to 0.94 Paper 0.70 to 0.94

Marble 0.94 Chromium Oxides 0.81

Plaster 0.80 to 0.90 Copper Oxides 0.78

Mortar 0.89 to 0.91 Iron Oxides 0.78 to 0.82

Brick 0.93 to 0.96 Textiles 0.90

Spot to Distance Ratio

The 8:1 spot to distance ratio determines the size of the measured surface area with

respect to the distance the meter is held away from the surface.

RH401 V1.4 11/07

Selecting temperature units of measure (C/F)

Press and hold the oC/oF button momentarily to toggle the temperature units.

Automatic Power OFF

The meter automatically shuts off after a programmed period of time.

To disable auto power off, with the meter off, press and . When “n” appears,

release the keys and the meter is now in Non-Sleep Mode.

The power off time is adjustable from 5 to 600 seconds. To change the auto power off

setting, press the key to enter the setting procedure. Use the up key and the

down key to set the value. When the desired power-off time appears in the display,

press the key again to save the parameters.

Backlight

Press the BKLT button to turn the display backlight on. The backlight will remain on until

the BKLT button is pressed again or the meter is turned off.

Error Messages

An error message will appear on the display if the meter fails an internal diagnostic test.

1. E1 (Top display): IR temperature failure. Repair/replacement is necessary.

2. E2 (Top display): IR temperature >932°F (500°C).

3. E3 (Top display): IR temperature <-40°F (-40°C).

4. E9 (Top display): Calibration error.

5. E1 (Middle display): Temperature failure. Repair/replacement is necessary.

6. E2 (Middle display): Dew Point is out of range or Repair/replacement is necessary.

7. E3 (Middle display): Air temperature is out of range or Repair/replacement is

necessary.

8. E1 (Bottom display): RH circuit error. Repair/replacement is necessary.

9. E5 (Bottom display): RH circuit error. Repair/replacement is necessary.

Setup memory

The selected display, emissivity value, auto power off time, backlight status and the laser

pointer status are stored in memory and will remain in memory as the user default setting

until reprogrammed by the user.

RH401 V1.4 11/07

Calibration

The following verification and calibration procedures requires a humidity chamber or the

33% and 75% RH reference bottles which are supplied with the Model RH405 kit.

RH Accuracy Verification

Checking the 33% or 75% RH Calibration

1. Insert meter’s sensor into the 33% or 75% salt reference

bottle.

Rotating the bottle will assist in placing it over the sensor.

2. Check the reading after 10 minutes

3. Verify that the reading is within the accuracy specification.

RH Calibration (33% and 75%)

This two point calibration takes approximately one hour to

complete.

33% Calibration

1. Turn off the meter and insert the meter sensor into the 33%

salt reference bottle. Rotating the bottle will assist in

placing it over the sensor.

2. Hold down the and keys and then press the

key to turn the unit on.

3. “32.8” (reading may vary depending on temperature) will

flash on the display. After 30 minutes, the flashing will stop

to indicate that the 33% calibration is complete.

75% Calibration

4. Insert the meter sensor into the 75% salt reference bottle. From a steady “32.8”

display press the button to enter the 75% calibration.

5. “75.2” (reading may vary depending on temperature) will flash on the display. After

30 minutes, the flashing will stop to indicate that the 75% calibration is complete

and the calibration data has been saved to memory.

6. The screen will return to the normal display. Calibration is now complete.

Note: If the salt at the bottom of the calibration bottles appears dry, the bottles should be

replaced.

33% or 75%

Cal Bottle

RH401 V1.4 11/07

RS-232 PC Communications Interface

RS-232 data format

Baud rate 9600

Parity none

Data bits 8

Stop bits 1

Flow control none

RS-232 Connection

Connect the optional interface cable from the meter to the communications port of the PC.

Using Windows® Terminal or HyperTerminal program for PC Communication

The Terminal or the HyperTerminal program is included in all Windows® operating systems.

Typically it is located using the following path:

START Menu > Programs > Accessories > Communications > Terminal or HyperTerminal

When in the Terminal or HyperTerminal program, configure as follows:

1. In the Connection Description window, enter a name, select an icon and click OK.

2. In the Connect To window, select COM1 or COM2 (depending on which port is being

used) and click OK.

3. In the Port Settings window, select the following data format: Baud rate 9600, no

parity, 8 data bits, 1 stop bit, and no flow control. Click OK to enter the main

HyperTerminal window.

4. In the File Menu, select Properties > Settings > ASCII SETUP, select “echo typed

characters” and “Send line ends with line feeds”. Click OK twice to return to the main

HyperTerminal window.

Format

Txxx.xC:Txx.xC:Hxx.x%:Txx.xC:Txx.xCLRCCRLF

Where: The 1st value is IR Temperature, the 2nd value is Air Temperature, the 3rd value is

Humidity, the 4th value is Wet Bulb, and the 5th value is Dew Point.

Format for error value: E01 no value; E02 Overflow; E03 Underflow

Unit for error code is n

For example: if IR is disabled: TE01n:T23.5C:H45.3%:T14.9C:T12.3CLRCCRLF

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 power falls low, the symbol will appear on the lower left of the LCD.

Replace the four (4) 1.5 ‘AAA’ batteries by removing the rear battery compartment cover

and accessing the battery compartment. Observe polarity when placing the batteries in the

compartment. Ensure that the compartment cover is securely fastened when finished.

RH401 V1.4 11/07



Support line (781) 890-7440

Technical support: Extension 200; E-mail: support@extech.com

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

Warranty

EXTECH INSTRUMENTS CORPORATION warrants the basic instrument to be free of

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

warranty applies on 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 EXTENSION 210 for authorization or visit www.extech.com

for more 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.

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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