Hanna Instruments HI 121 - Manual (Page 13)

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The temperature can be adjusted with the ARROW keys or the numerical
keypad (from –20.0 ºC to 120.0 ºC or from –4.0 ºF to 248.0 ºF).
Press NUM to change the temperature value with the numerical keys. The
“2nd” tag will blink. Press CLR or 2nd then CLR if you want to delete
digits of the displayed value. The remaining digits will shift to right.
Introduce the desired value. If the value is out of temperature range, a
long beep will be heard. Press NUM to confirm the new value or CAL to
escape without changing the temperature.
mV/ORP MEASUREMENTS
Oxidation-reduction potential (REDOX) measurements provide the quantification
of the oxidizing or reducing power of the tested sample.
To correctly perform a redox measurement, the surface of the ORP electrode
must be clean and smooth.
• Press MODE or simply mV from the left keyboard to
enter mV range.
• Submerge the tip of the ORP electrode (4 cm/1½”)
into the sample to be tested and allow a few
seconds for the reading to stabilize.
• The instruments display the mV reading on the primary LCD and the
temperature on the secondary LCD, along with “Channel” and “ORP”
tags if a Hanna ORP electrode with pin is used.
Note: If an ORP electrode with pin is not detected, “Channel”, “pH” and
“ORP” tags will be displayed on the LCD.
• If the reading is out of range, the closest full-scale value will be
displayed blinking on the primary LCD.
RELATIVE mV MEASUREMENTS
To enter Relative mV mode, press MODE or simply RelmV from the left
keyboard. The relative mV reading will be displayed on the primary LCD and
the current temperature value on the secondary LCD.