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Big Digit
Remote Probe
Hygro-Thermometer
Model 445715
Introduction
Congratulations on your purchase of the Extech Big Digit Remote Probe Hygro-Thermometer. It features Humidity and Temperature
readouts and can be calibrated using the optional calibration salt bottles (order no. 445580-C). The remote probe conveniently mounts on
the meter (1) or extends for measurements in ducts or other remote locations.
Operation
1. Open the battery compartment (7) by pushing the cover (11) on the rear of the instrument downward as indicated by the arrow and
remove battery safety strip.
2. Remove the protective cover on the LCD display (2) and take the Probe out of the probe compartment (6). The meter is now ready for
use.
3. The temperature units (
o
F/
o
C) can be selected via the switch (9) located in the battery compartment.
4. The upper display indicates the temperature. The lower display indicates humidity.
5. Displaying the minimum and maximum values:
a. Press the MAX/MIN button (3). The highest value measured since the Reset button (4) was last pressed appears on the display.
b. Press the MAX/MIN button again to display the lowest value measured since the Reset button was last pressed.
c. Press the MAX/MIN button again to return to normal display operation.
6. Resetting (clearing) the MAX/MIN memory. Press and hold the RESET button (4) for 1 second while in the MAX/MIN display mode to
clear the memory and start recording new max/min values.
7. User can select wall-mounting (5) or flat surface use with fold-out footing (7).
8. The low battery icon will appear on the display when the battery voltage is low. Replace the battery when this occurs.
Battery Replacement
Slide the rear battery cover (11) downward as indicated by the arrow. Replace the 1.5V ‘AAA’ battery and replace the cover.
Calibration
The following verification and calibration procedure requires a humidity chamber or the optional 33% and 75% RH reference bottles (order
no. 445580-C).
RH Accuracy Verification (Checking the 33% or 75% RH Calibration)
1. Insert meter’s sensor (1) into the 33% or 75% salt bottle or humidity chamber.
Note: Slowly rotating the bottle will assist in placing it over the sensor.
2. Allow the meter to stabilize for 1 hour at the reference RH and then verify that the reading is within the accuracy specification.
RH Calibration
1. Insert meter’s sensor into a 75% salt reference bottle or humidity chamber.
2. Check the reading after 1 hour.
3. Adjust the RH calibration pot (8) in ½ turn increments, waiting for the display to update after each adjustment, until the reading is
within specification.
4. Repeat the RH accuracy verification procedure.
Note: Replace bottle if the salt at the bottom of the calibration bottle appears dry.
Temperature Calibration
1. Place the sensor in a stabilized environment of approximately 70°F (21°C).
2. Check the reading after 1 hour.
3. Adjust the temperature calibration pot (10) in ½ turn increments, waiting for the display to update after each adjustment, until the
reading is within specification.
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