Hanna Instruments HI 98170 - Manual (Page 10)

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In order to take more accurate pH measurements, make sure that the
instrument is calibrated (see page 12 for details).
It is recommended that the electrode is always kept wet and rinsed thoroughly
with the sample to be measured before use.
The pH reading is directly affected by temperature. In order for the instrument
to measure the pH accurately, temperature must be taken into consideration. If
the sample temperature is different from the temperature at which the pH
electrode was kept, allow a few minutes to reach thermal equilibrium.
To use the instrument's Automatic Temperature Compensation feature, submerge
the temperature probe into the sample as close to the electrode as possible and
wait for a few seconds.
If manual temperature compensation (MTC) is desired, the temperature
probe must be disconnected from the instrument.
The display will show the default temperature of 25 ºC,
the last measured temperature reading, or the last set
temperature, with the “ºC” (or “ºF”) tag blinking.
The “MTC” tag and up & down arrows symbols light up on the LCD to indicate
that the instrument is in MTC mode and the arrow keys can be used to enter
the desired temperature value.
Note: When in MTC the user can press and hold the ARROW keys, and the
instrument will start incrementing / decrementing the temperature value.
The instrument keeps measuring and the display is updated periodically.
ORP MEASUREMENTS (HI 98171 & HI 98172 only)
To perform ORP measurements, connect an optional ORP electrode (see Accessories
section) to the instrument and turn it ON.
If necessary, enter the mV mode by pressing RANGE
until the display changes to mV.
Submerge the ORP electrode tip (4cm/1½”) into the
sample to be tested and wait a few seconds for the
reading to stabilize.
Measurements within the ±699.9 mV range are
displayed with 0.1 mV resolution, while outside this
range the resolution automatically switches to 1 mV.
The “ATC” (or “MTC”) tag is turned off because mV
readings are not temperature compensated.
For accurate ORP measurements, the surface of the electrode must be clean
and smooth. Pretreatment solutions are available to condition the electrode
and improve its response time (see Accessories section, page 45).
RELATIVE mV MEASUREMENTS (HI 98171 & HI 98172 only)
To enter Relative mV mode, press 2nd then MODE
while in mV measurement mode. The relative mV
reading will be displayed on the primary LCD and the
current temperature value on the secondary LCD.