Extech Instruments RH305 User manual

USER GUIDE
Digital Psychrometer
Models RH300 and RH305 (kit)
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Extech RH305 Hygro Thermometer Psychrometer Kit
Extech RH305-NIST Hygro Thermometer Psychrometer Kit

RH300-EU-EN v1.6 9/13
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Introduction
Congratulations on your purchase of the Extech RH300 Digital Psychrometer. This device measures
Humidity, Air Temperature, Dew Point temperature and Wet Bulb temperature. Advanced features
include External Temperature Measurement (with optional probe), Data Hold, selectable Auto Power
Off, and MAX/MIN/Average reading. Careful use of this meter will provide years of reliable service.
Meter Description
1. Humidity Sensor & Air Temperature Sensor
2. Triple LCD Display
3. ON/OFF button
4. T1-T2/Dew Point/T1 button
5. °F/°C select
6. MIN/MAX/RESET button
7. T2-DP/Wet Bulb/T2 button
8. HOLD
button
9. T2 Probe Jack
Note: The battery compartment is located
on the rear of the instrument
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RH300-EU-EN v1.6 9/13
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/WB
T2
T/DP
T1
1
2
3
4
56
7
8
9
10
11
Display Description
1. Relative Humidity %
2. T1
3. T1-T2
4. Dew Point
5. Wet Bulb
6. T2-Dew
Point
7. °C/°F
8. T2
9. Maximum
10. Minimum
11. Low Battery/Hold
Operation
Open the Protective Sensor Cap
Twist the protective sensor cap, located at the top of the
meter, counter-clockwise a quarter of a turn to expose the
sensor
Plug in the optional external temperature probe (if
needed).
Turn Power ON or OFF
Press the ON/OFF button to turn power on or off. The meter will perform a short self-test when
turned on.
Taking measurements
1. Hold the probe in the area to be tested.
2. Allow adequate time for readings to stabilize.
3. The Relative Humidity measurement appears in
the top display.
4. Pressing the button toggles the lower left
display between T1-T2 (internal temperature-
external temperature), DP (Dew Point), and T1
(internal temperature).
5. Pressing the button toggles the lower right
display between T2-DP (external temperature-
Dew Point), WB (Wet Bulb), and T2 (external
temperature).
Note: If the external probe is not connected, T1-T2, T2-DP, and T2 measurements will not be
displayed.
Selecting temperature units of measure (C/F)
Press and hold the oC/oF button momentarily to toggle the temperature units.
CLOSE OPEN
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RH300-EU-EN v1.6 9/13
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/WB
T2
T/DP
T1
Wet Bulb and Dew Point measurements
1. To read the Wet Bulb measurement, press the button until the symbol Wb appears in the
lower right display. Note: T2 will not be displayed unless the external probe is connected.
2. Wet Bulb temperature is now displayed.
3. To read the Dew Point measurement, press the button until the symbol DP appears in the
lower left display .
4. Dew Point temperature is now displayed.
Minimum (MIN) Maximum (MAX) Function
The MIN/MAX mode allows the user to view only the lowest (MIN) or highest (MAX) readings. Press
the
RESET
MX/MN
button once and MIN appears on the display. The display is now showing the lowest
humidity and temperature reading in memory. Press the
RESET
MX/MN
button again and MAX appears on
the display. The display is now showing the maximum humidity and temperature readings in
memory. To exit the MIN/MAX mode, press the
RESET
MX/MN
button again and the MIN and MAX icons
disappear. To clear the current min/max readings in memory, press and hold the
RESET
MX/MN
button for
more than two seconds.
Data Hold
Press the HOLD button momentarily to freeze the displayed reading. The 'HLD' icon will appear on
the upper right-hand side of the display. Press the HOLD button again to return to normal operation.
Automatic Power OFF
The meter automatically shuts off after a programmed period of time. The default time is 10 minutes.
To program the time period, press down the HOLD button while turning the meter on. Continue to
hold down both buttons and the meter will cycle through the selectable power-off times: n, 2, 5, 10,
20, 40 or 60 minutes. “n” disables the auto power off function. When the desired power-off time
appears in the display, release both buttons to select the time and return to normal operation.
Error Messages
An error message will appear on the display if the meter fails an internal diagnostic test.
1. ER1: Relative Humidity failure. Repair/replacement is necessary.
2. ER2: Internal temperature failure. Repair/replacement necessary.
3. ER3: Reference resistance failure. Repair/replacement necessary.
4. ER4: Internal temperature is out of range.
5. ER5: External temperature is out of range.
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RH300-EU-EN v1.6 9/13
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Calibration
The following verification and calibration procedures require the 33% and 75% RH reference bottles
which are supplied with the Model RH305 kit.
Accuracy Verification
Checking the 33% or 75% RH Calibration:
1. Insert meter’s sensor into the 33% or 75% salt reference bottle.
2. Check the reading after 10 minutes.
3. Verify that the reading is within the accuracy specification.
Relative Humidity Calibration (33% and 75%)
Calibration Preparation
Ensure that fresh batteries are installed in the meter.
Move the protective vent cap to the Open position.
Power the meter ON and set it to display dew point (DP) and wet bulb (Wb) in the lower display
area.
Calibration Procedure
1. Follow the Preparation steps above before continuing.
2. Power the meter OFF.
3. Insert the meter into a 33% salt bottle.
4. Leave the meter OFF for one hour (to stabilize).
5. After the meter has stabilized for one hour:
Press and hold the °C/°F button while powering the unit ON.
The unit enters calibration mode (32.8% flashes on the display).
The DP and Wb display areas show DP ---- Wb ----°C.
6. Once the 33% calibration is complete, the display stops flashing and a constant 32.8% is
displayed.
7. Allow the meter to remain ON and move it to the 75% salt bottle.
8. Allow the meter to remain for one hour in the 75% salt bottle to stabilize.
Important: Do NOT power the meter OFF while in the Calibration mode! Note that
AUTO POWER OFF is disabled while in the Calibration mode.
9. After one hour, press and hold the MN/MX button until 75.3% begins flashing on the meter
display. The meter has now entered the 75.0% calibration stage.
10. After 30 minutes have elapsed, the meter will automatically exit the calibration mode and
return to the normal operating mode.
11. The Calibration is complete, turn power OFF.
Note: To exit from the calibration procedure before completion, press the ON/OFF button.
Note: If the salt at the bottom of the calibration bottles appears dry, the bottles should be replaced.
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RH300-EU-EN v1.6 9/13
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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 LCD. Replace the two (2) 1.5
‘AAA’ batteries by removing the rear battery compartment cover and accessing the battery
compartment. Observe correct polarity when placing the batteries in the compartment. Ensure that
the compartment cover is securely fastened when finished.
EU Directive: 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
oNever dispose of batteries in a fire. Batteries may explode or leak.
oNever mix battery types. Always install new batteries of the same type.
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RH300-EU-EN v1.6 9/13
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Specifications
Range and Resolution Accuracy
Humidity 0.0 to 100.0% RH ±3% RH (10 to 90%) @ 23oC
Temperature (internal) -20 to 50oC (-4.0 to 122.0oF) ±1oC (±1.8oF)
Temperature (external) -20 to 70oC (-4.0 to 158.0oF) ±1oC (±1.8oF)
Display Triple LCD
Sensor Type Humidity: Precision capacitance sensor
Temperature: Thermistor
Response Time 60 seconds typical
Dew Point -90.4 to 122.0oF (-68 to 50oC) (calculated from RH and Air temperature
measurements)
Wet Bulb -6.88 to 122.0oF (-21.6 to 50oC) (calculated from RH and Air
temperature measurements)
Operating Conditions -20 to 50oC (-4 to 122oF); < 99% RH non-condensing
Storage Conditions -40 to 85oC (-40 to 185oF); <99% RH non-condensing
Power Supply 2 x 1.5V ‘AAA’ batteries
Battery Life Approx. 80 hours
Dimensions / Weight 178.5 x 48.8 x 25.2mm (7 x 1.9 x 1”); 140g (4.9 oz.)
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