Extech Instruments RH101 User manual

User's Guide
Hygro-Thermometer + InfraRed Thermometer
Model RH101
Patented

RH101-EU V3.0 11/07
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Introduction
Congratulations on your purchase of the Extech Hygro-Thermometer plus InfraRed
Thermometer. This device measures relative humidity, air temperature (with probe), and
surface temperature (with the InfraRed function). The large, easy-to-read backlit LCD
includes primary and secondary displays plus numerous status indicators. The InfraRed
feature includes a laser pointer for convenient targeting. Careful use of this meter will
provide years of reliable service.
Specifications
Display Dual LCD with Backlight and status indicators
Sensor Type Humidity: Precision capacitance sensor
Temperature: Thermistor (probe) and InfraRed
Response Time IR Temperature: 0.5 seconds; Probe Temperature and
Relative Humidity: 3 minutes
Accuracy note Accuracy is specified for the following ambient temperature
range: 64 to 82°F (18 to 28°C)
Sampling Rate 2.5 samples per second
InfraRed Emissivity 0.95 (fixed)
IR Field of View D/S = Approx. 8:1 ratio (D = distance, S = spot)
Laser power Less than 1mW
IR Spectral Response 6 to 14 μm (wavelength)
Operating Conditions 32 to 122oF (0 to 50oC); < 80% RH non-condensing
Storage Conditions 14 to 140oF (-10 to 60oC); <80% RH non-condensing
Power Supply 9V Battery with auto power off (after 10 minutes)
Battery Life Approx. 24 hours (if Backlight and Laser are used continuously
the battery life is reduced to 2 to 3 hours approx.)
Dimensions / Weight 5.9 x 2.8 x 1.4” (150 x 72 x 35mm); 8.3 oz. (235g)
Patent Notice U.S. Patent 7168316
Safety
•Use extreme caution when the laser pointer beam is on
•Do not point the beam toward anyone's eye or allow the beam
to strike the eye from a reflective surface
•Do not use the laser near explosive gases or in other
potentially explosive areas
Function Range and Resolution Accuracy
Humidity 10.0 to 95.0% RH ± 3.5% RH
Air Temperature -4 to 140oF (-20 to 60oC) ± 3.0oF (± 2.0oC)
-58.0 to -4.0oF (-50.0 to -20.0oC) ± 9oF (± 5oC)
-4.0 to 199.9oF (-20.0 to 93.3oC)
200 to 400oF (93oC to 204oC) ± 2% of rdg or ± 4oF (± 2oC)
IR Temperature
400 to 932oF (204oC to 500oC) ± 3% of rdg

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Meter Description
1. Humidity/Air Temperature Probe
2. Probe input jack
3. Laser pointer
4. IR Sensor
5. Rubber holster
6. LCD Display
7. IR thermometer measurement button
8. IR and Relative Humidity function buttons (4)
9. Air Temperature function buttons (3)
10. Probe holder
11. Power ON/OFF button
12. Backlight button
Note: The battery compartment, tilt stand, tripod mount, and probe holder removal screw
are located on the rear of the instrument
Display Layout
•MAX (top of LCD): Max Hold function engaged for the Air Temperature function
•HOLD (top of LCD): Data Hold function engaged for the Air Temperature function
•PROBE TEMP: Reminder that the top LCD digits represent Air (Probe) Temperature
•: Indicates that the laser pointer is on.
•IR TEMP: Indicates that the larger LCD digits represent IR temperature measurement
•MAX (bottom of LCD): Max Hold for the IR Temperature and RH function
•HOLD (bottom of LCD): Data Hold for the IR Temperature function and RH function
•oC / oF: Temperature units of measure
•%RH: Relative Humidity unit of measure
•Large LCD digits at center of display for Relative Humidity and IR Temperature
•Smaller LCD digits at top, right of display for Probe Temperature
•: Low battery indicator

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Operation
Power
Press the button to turn power on or off.
Probe Humidity and Temperature Measurements
1. Attach the probe to the meter via the jack at the top of the meter.
2. Hold the probe in the area to be tested & allow adequate time for readings to stabilize.
3. Read the Relative Humidity (center of LCD) and Probe Temperature (top of LCD).
NOTE: Do not immerse the probe in liquid; it is intended for use in air only.
InfraRed (Non-Contact) Temperature Measurements
1. The IR sensor is located at the top of the meter.
2. Point the sensor toward the surface to be measured.
3. Press and hold the large red IR button to begin measuring the surface
temperature of a desired target. IR TEMP and will appear on the
display. The laser pointer will switch on to help aim the meter.
4. The measured IR surface temperature will appear at the center of the
LCD (larger digits). The temperature displayed is the temperature of the
area within the spot.
5. When the red IR button is released, the laser pointer will switch off and
the reading will freeze (data hold) on the display for approx 10 seconds.
6. Note that the probe (Air Temperature wand) continues to monitor
temperature during IR tests and its temperature is displayed on the top
of the LCD (smaller digits).
7. After approx. 10 secs. the meter defaults to the Humidity and Air
Temperature display.
Automatic Power OFF
To conserve battery life the meter automatically shuts off after 10 minutes.
oF/oC buttons
The Air Temperature and the IR Temperature units can be selected by the user. For Air
Temperature, press the oF/oCbutton on the bottom left. For the IR temperature units, press
the oF/oCbutton at the center of the meter.
Data Hold Buttons
Displays can be held (frozen) at any time by pressing the HOLD button. For Air
Temperature, use the HOLD button on the bottom right. For IR Temperature and for
Relative Humidity, use the HOLD button on the right center of the meter. Press HOLD
again to exit the mode. Note that in IR temperature mode Data Hold is automatically
engaged when the red IR button is released.
MAX Buttons
Press the MAX button (bottom of meter for Air Temperature; center of meter for IR
temperature and Relative Humidity) to display only the highest reading. The displayed
measurement will now only change when a higher reading is detected. Press the MAX
button again to exit this mode.
Backlight Press the backlight button to turn the light on. Press again to turn it off.
IR
Spot

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InfraRed Measurement Considerations
•When taking IR measurements the meter automatically compensates for ambient
temperature changes. Note that it may take up to 30 minutes to adjust to extremely
wide ambient changes.
•Low temperature measurements quickly followed by high temperature measurements
may require several minutes to stabilize as a result of the IR sensor cooling process.
•If the surface of the object under test is covered with frost, oil, grime, etc., clean before
taking measurements.
•If an object's surface is highly reflective apply masking tape or flat black paint before
measuring.
•Steam, dust, smoke, etc. can obstruct measurements.
•To find a hot spot, aim the meter outside the area of interest then scan across (in an up
and down motion) until the hot spot is located.
IR Theory
IR thermometers measure the surface temperature of an object. The meter’s optics sense
emitted, reflected, & transmitted energy that is collected and focused onto the meter’s
detector. The meter’s circuitry translates this information into an LCD reading.
IR Field of View
Ensure that the desired target is larger than the spot size as shown in the diagram below.
As the distance from an object increases, the spot size of the area measured by the meter
becomes larger. The meter’s field of view ratio is 8:1, meaning that if the meter is 8 inches
from the target, the diameter (spot) of the object under test must be at least 1 inch. Other
distances are shown below in the field of view diagram.
Emissivity
Most organic materials and painted or oxidized surfaces have an emissivity of 0.95 (fixed
setting in the model RH101). Inaccurate readings will result when measuring shiny or
polished surfaces. To compensate, cover the surface under test with masking tape or flat
black paint. Allow time for the tape to reach the same temperature as the material
underneath then measure the temperature of the tape or the painted surface.
Distance to Object in inches
Diameter of S
p
ot in inches
0.75” 1” 1.25”
6” 8” 10” 12”
1.5”

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Thermal Emissivity Table for Common Materials
Material Emissivity
Asphalt 0.90 to 0.98
Concrete 0.94
Cement 0.96
Sand 0.90
Earth 0.92 to 0.96
Water 0.67
Ice 0.96 to 0.98
Snow 0.83
Glass 0.85 to 1.00
Ceramic 0.90 to 0.94
Marble 0.94
Plaster 0.80 to 0.90
Mortar 0.89 to 0.91
Brick 0.93 to 0.96
Cloth (black) 0.98
Human skin 0.98
Lather 0.75 to 0.80
Charcoal (powder) 0.96
Lacquer 0.80 to 0.95
Lacquer (matt) 0.97
Rubber (black) 0.94
Plastic 0.85 to 0.95
Timber 0.90
Paper 0.70 to 0.94
Chromium oxides 0.81
Copper Oxides 0.78
Iron Oxides 0.78 to 0.82
Textiles 0.90
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.

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Battery Replacement
The battery symbol appears on the lower right of the LCD when the 9V battery needs
to be replaced.
Replace the 9V battery as follows:
1. Turn the meter off and disconnect the air temperature probe.
2. Remove the large flat-head screw on the rear of the meter to remove the probe holder.
3. Remove the rubber holster that surrounds the entire meter by pulling it over the top of
the meter.
4. Remove the small Phillips head screw on the rear of the meter.
5. Open the battery compartment and replace the 9V battery.
6. Re-assemble the meter before operating.
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, gratuitously, at the
collection points for our branches 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
WARNING: To avoid electric shock, do not operate the meter until the battery cover is in
place and fastened securely.
NOTE:: If your meter does not work properly, check the fuses and batteries to make sure that
they are still good and that they are properly inserted.
Calibration
A humidity calibration adjustment is located in the battery compartment.
1. Remove the battery door and move the battery to one side.
2. Place the humidity probe in a humidity chamber or humidity
calibration bottle and wait 20 minutes
3. Turn the meter on and turn the adjustment until the humidity reading
on the display agrees with the calibration source.
Copyright ©2007 Extech Instruments Corporation.
All rights reserved including the right of reproduction in whole or in part in any form.
Battery
Compartment
Cal
Adjust