MODEL 315 HUMIDITY TEMPERATURE METER
4.0Operating Instructions:
4.1Preparation for Measurement:
To measure ambient humidity and temperature, hold the instrument in the environment of interest and allow sufficient time for the sensors to respond to ambient conditions. (See Section 2.0 – Response Time.)
4.2Power:
Press the 
button to turn the instrument ON or OFF.
4.3Selecting the Temperature Scale
When first turned on, the instrument defaults to reading in Celsius (°C). The instrument toggles between Celsius (°C) and Fahrenheit (°F) each time the °C/°F button is pressed. The instrument remembers the scale setting when last turned off and powers on in that setting the next time.
4.4Data-Hold Function
The present reading is held on the display by pressing the HOLD button. Pressing the HOLD button again releases the hold function and returns the instrument to continuous reading.
In the HOLD mode, the UREL, MAX MIN and °C/°F buttons are disabled, as indicated by two consecutive beeps when pressed.
4.5Relative Operation
Pressing the UREL button internally memorizes the present reading and the main display shows the difference between the new reading and the memorized value. Press the UREL button again to exit the Relative operation.
4.6MAX/MIN Operation
Press the MAX MIN button to enter the MAX/MIN mode. In this mode, both the maximum and minimum values are simultaneously retained in memory and updated with every new data sample. The instrument first enters the MAX mode, and the MAX symbol and value are both displayed. Pressing MAX MIN again advances the display to the MIN symbol and value. The next press of the MAX MIN button will cause both the MAX and MIN symbols to blink. This indicates that the maximum and minimum values have been updated in memory and the displayed reading is the present value. Each successive press of the MAX MIN button circulates the display mode among these options. To exit the MAX/MIN mode, press and hold MAX MIN for two seconds.
In the MAX/MIN mode, the, UREL and °C/°F buttons are disabled, as indicated by two consecutive beeps if pressed.
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MODEL 315 HUMIDITY TEMPERATURE METER
4.7Auto Power Off
By default, the instrument powers on in the ‘Auto Power Off’ mode and will automatically shut off 30 minutes after the last key operation.
To disable this feature, press and hold the HOLD button and then power on the meter. Two successive beeps indicate that ‘Auto Power Off’ is disabled.
4.8Low Battery Condition
When the battery voltage is at or below the minimum for proper operation,
the 
symbol will show on the display indicating that the battery must be replaced.
4.9Calibration Points:
Room temperature: 23°C ± 5°C
Temperature calibration points: 0°C and 40°C
Humidity calibration points: 32.8% RH@25°C and 75.3% RH@25°C
5.0Calibration Procedure:
Note: Conduct temperature calibration before humidity calibration.
5.1Temperature Calibration
1.Turn the unit off. Press and hold the HOLD and °C/°F buttons. While these two buttons are pressed, turn the power on. Release all buttons and all the segments on the display will blink.
2.Within 3 seconds of releasing these buttons, again press the °C/°F button to enter the calibration mode, or the instrument will revert to normal operating mode.
3.Upon entering the calibration mode, ‘CAL1’ will appear on the second display.
4.Insert the probe into a
5.Insert the probe into a
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