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Heat
Index
Psychrometer
Model RH25
USER
GUIDE
Introduction
Thank you for selecting the Extech Instruments Model RH25 Heat Index Psychrometer.
The RH25 measures Temperature and Relative Humidity (using precision capacitance RH sensor).
The RH25 also calculates and displays Heat Index, Dew Point, Wet Bulb, and Wet Bulb Globe temperatures.
The High Temperature Alarm feature alerts the user when Heat Index or Wet Bulb Globe levels exceed user ‐ preset limits.
Data Hold and MIN/MAX/AVG memory utilities make it easier to recall important data.
This device is shipped fully tested and calibrated and, with proper use, will provide years of reliable service.
Please visit our website (www.extech.com) to check for the latest version of this
User Guide, Product Updates, and Customer Support.
Description
Meter
1.
Sensor area
2.
Display area (LCD)
3.
POWER button
4.
HOLD button
5.
MODE button
6.
Battery compartment on rear of instrument
Display
TEMP Temperature
AIR T Air Temperature
RH Relative Humidity
HI Heat Index
DP Dew Point temperature
WB Wet Bulb temperature
WB/HI Wet Bulb Globe temperature
MAX Maximum reading memory
MIN Minimum reading memory
AVG Average reading memory
HOLD Data Hold (freezes display)
BAT Low Battery symbol
% o
Percent
Degrees
units for symbol
RH for
readings temperature units
E
Used to display temperature units C or F
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Operation
Keypad
POWER: Switch the meter ON or OFF; also used to enter the MAX/MIN/AVG memory mode.
HOLD: Press to enter Data Hold (reading freezes on display).
Press again to exit Data Hold.
MODE: Press to step through the measurement modes: TEMP (Temperature), RH (Relative
Humidity), HI (Heat Index), DP (Dew Point), (WB (Wet Bulb), and HI/WB (Wet Bulb Globe).
Powering the meter
Press POWER to switch meter ON.
The meter shows all display icons momentarily as it switches
ON and then the TEMP icon and the temperature reading will display.
The meter will also emit a chirp sound as it switches ON.
To switch the meter OFF, press and hold the POWER button for at least 2 seconds.
MAX/MIN/AVG Memory
With the meter powered ON, press POWER button momentarily.
The MAX icon will appear and the meter will display only the highest reading.
Press POWER again; the MIN icon will appear and the meter will only display the lowest reading.
Press POWER again; the AVG icon will appear and meter will only display the average reading.
Press POWER again to exit (the MAX/MIN/AVG icons will switch OFF).
Data Hold
With the meter powered ON, press the HOLD button momentarily.
The HOLD icon will appear and the current reading will freeze on the display.
Press HOLD again to exit (the HOLD icon will switch OFF).
Automatic Power OFF (Sleep) Mode
The meter switches OFF automatically after 15 minutes of inactivity.
To defeat this feature temporarily: With the meter switched OFF, press the HOLD and POWER buttons simultaneously until the meter displays the screen shown below.
Now, the user must switch the meter OFF manually by pressing and holding the POWER button for at least 2 seconds.
Note that the next time the meter’s power is cycled, the Auto Power OFF utility will again be active.
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Selecting o
C/ o
F units of measure
With the meter OFF, press and hold the POWER and MODE buttons simultaneously until the unit of measure appears on the lower right corner of the LCD.
Use the MODE button to select the desired unit of measure ( o
C or o
F).
Press POWER twice to step past the alarm settings until the normal measurement mode is displayed.
High Alarm for Heat Index and Wet Bulb Globe temperature
1.
With the meter OFF, press and hold the POWER and MODE buttons simultaneously until the temperature unit ‘C’ or ‘F’ appears on the lower right corner of the LCD (if desired, use the
MODE button to select the desired unit of measure).
2.
Press the POWER button to step to the Heat Index (HI) Alarm ON/OFF display.
3.
Use the MODE button to select ON (A ‐ on) or OFF (A ‐ oF); see display examples below:
4.
Press POWER to step to the Heat Index temperature Alarm limit value.
See example below:
5.
Press the MODE button momentarily to change the value in small steps.
Press and hold the
MODE button to scroll quickly.
6.
When the desired Heat Temperature alarm limit is displayed, press the POWER button to continue to the Wet Bulb Globe temperature Alarm programming screens.
7.
Repeat steps 3 ‐ 6 to program the Wet Bulb Globe temperature ON/OFF and Alarm limits.
Use the POWER button when done to step back to the normal operating mode.
8.
The default settings are 27.8
o
C (82.0
o
F) for Heat Index temperature alarm limits and 28.0
o
(82.4
o
F) for Wet Bulb Globe temperature alarm limits
C
9.
When either alarm limit is exceeded, the meter continuously beeps.
To determine which alarm is sounding, check the HI (Heat Index) and WB/HI (Wet Bulb Globe) temperature displays to see which unit of measure is blinking, that will indicate the tripped alarm.
10.
To silence an alarm the user must either switch the alarm OFF or change its alarm limit value.
Error Message Displays
E ‐ 2: Humidity Sensor failure.
Replace unit.
E ‐ 3: Temperature Sensor failure.
Replace unit.
E ‐ 4: Temperature over ‐ range; E ‐ 5: Temperature under ‐ range
E ‐ 6: Hardware failure.
Replace unit
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Appendices
Appendix A – Heat Index based on Temperature ( o
F) vs.
Relative Humidity (%)
Note: Italic values are Heat Index based on the Temperature (left column) and Relative Humidity (top row).
o
F 90% 80% 70% 60% 50% 40%
80
o
F
85
o
F
85
101
84
96
82
92
81
90
80
86
79
84
90
o
F
95
o
F
100
o
F
121
105
o
F
110
o
F
113
133
105
122
142
99
113
129
148
94
105
118
133
90
98
109
121
135
Appendix B – Heat Index based on Temperature ( o
F) vs.
Dew Point (DP)
Note: Italic values are Heat Index based on the Temperature (left column) and Dew Point (top row).
o
F 55 DP 60 DP 65 DP 70 DP 75 DP 80 DP 85 DP
80
o
F
85
o
F
55
80
60
80
65
81
83
89
84
93
87
99
107
90
o
F
95
o
F
100
o
F
105
o
F
110
o
F
84
86
91
95
101
100
106
113
107
114
121
127
134
117
125
131
138
145
Appendix C – Heat Index and Health Effects
Heat Index of 80 to 90 o
F: Fatigue possible with prolonged exposure and physical activity
Heat Index of 90 to 105 o
F: Sunstroke, heat cramps, and heat exhaustion possible
Heat Index of 105 to 130 o
F: Sunstroke, heat cramps, heat exhaustion likely; heat stroke possible
Heat Index of 130 o
F or greater: Heat stroke highly likely with continued exposure
The Heat Index is determined using the dry bulb temperature and the relative humidity.
It is based on charts available through the U.S.
National Weather Service.
The Heat Index represents how an average person feels relative to climate conditions.
For a given temperature, the higher the humidity, the higher the heat index will be.
5 RH25 ‐ EU ‐ EN v1.0
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Battery Replacement
When the low battery icon (BAT) appears on the LCD, the CR ‐ 2032 lithium button battery must be replaced.
The battery compartment is located on the rear of the meter.
1.
Use a coin to turn the battery compartment cover counter ‐ clockwise to open.
2.
Note the position, orientation, and polarity of the existing battery installation.
3.
Replace the CR ‐ 2032 Lithium battery following the same position, orientation, and polarity.
4.
Replace the battery compartment cover and secure it using a coin to turn it clockwise
Never dispose of used batteries or rechargeable batteries in household waste.
As consumers, users are legally required to take used batteries to appropriate collection sites, the retail store where the batteries were purchased, or wherever batteries are sold.
Disposal: Do not dispose of this instrument in household waste.
The user is obligated to take end ‐ of ‐ life devices to a designated collection point for the disposal of electrical and electronic equipment.
Other Battery Safety Reminders o Never dispose of batteries in a fire.
Batteries may explode or leak.
o Never mix battery types.
Always install new batteries of the same type.
Specifications
Display
Measurement ranges
Air Temperature
Heat Index
Dew Point
Wet Bulb
Wet Bulb Globe
Relative Humidity
Resolution
Accuracy
Temperature
Relative Humidity
Power supply
Dimensions
Weight
Multi ‐ function LCD
‐ 20 to 50 o
C ( ‐ 4 to 122 o
F)
‐ 46 to 205 o
C ( ‐ 50.8
to 401 o
F)
‐ 78 to 50 o
C ( ‐ 108.4
to 122 o
F)
‐ 20 to 50 o
C ( ‐ 4 to 122 o
F)
‐ 25 to 54.5
o
C ( ‐ 13 to 130 o
F)
0 to 99.9% RH
0.1
o
C/
o
F/%RH
±0.6
o
C (1 o
F)
±3%RH @ 25
o
C from 10 to 90% RH otherwise ±5% RH
1 x CR2032 Lithium Battery
140 x 35 x 18mm (5.5
x 1.4
x 0.7")
50g (1.8
oz.)
Copyright © 2013 FLIR Systems, Inc.
All rights reserved including the right of reproduction in whole or in part in any form www.extech.com
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