12 13
Note If the probe offset is outside the allowed limits, if the HI 504910
transmitter is configured for ORP measurement, or if some other
error occurs during calibration, the display will flash a “bAd”
message. Press TXCAL to return to normal mode and restart the
calibration procedure from the beginning.
• The primary LCD will then display the
pH reading of the HI 504910 trans-
mitter, while the secondary LCD will
show the HI 504920 reading. Both pH
tags blink alternatively.
Note The two values may differ a little if the measured solution is
not stable. For an accurate calibration, perform the single
point procedure only when readings are stable.
• To exit the calibration mode, press TXCAL.
Note It is advisable to perform the entire calibration procedure
keeping the HI 504920 meter and the HI 504910 trans-
mitter connected through the infrared optical interface.
• It can happen that HI 504910 is positioned in a difficult-
to-reach place while the pH probe of HI 504920 is im-
mersed in the solution: the two instruments will be not con-
nected, and when the primary LCD shows the blinking
“CALt” message, the secondary display will show a count-
down starting from 120 seconds. In this situation, the pH
probe can be taken out of the solution, while the interface
cable has to be connected to the HI 504910 transmitter
before the countdown reaches zero. Calibration then con-
tinues, and at the end of the procedure the pH tag of the
secondary LCD will not blink.
Note If the infrared cable is not connected before the end of the
countdown, the LCD shows the “tiMEout” message and the
calibration is not completed.
Note It is possible to check the HI 504910 pH reading against
the HI 504920 pH reading at any time, without calibrating
the HI 504910 transmitter.
• Press (ALT+) TXCAL.
• The primary display will
show the HI 504910 pH
reading, while the sec-
ondary LCD displays the
CALIBRATION MODE
The calibration mode allows to calibrate the pH/ORP and
temperature inputs.
The instrument is factory calibrated for all these parameters.
Periodical calibration of the instrument is recommended, in
particular when greatest accuracy is required and at least bi-
yearly.
The electrode can be calibrated over only one point but,
when possible, it is always good practice to perform a 2-
point calibration.
QUICK SINGLE-POINT pH CALIBRATION (through HI 504920)
A quick single point pH calibration at the pH value of the
solution monitored by HI 504910 transmitter can be per-
formed. HI 504920 serves as a reference pH meter.
Unlike the usual calibration with buffers, this quick proce-
dure is carried out without having to interrupt normal
measurement.
Note For better accuracy, from time to time it is recommended to
perform a 2-point calibration procedure, which allows to ad-
just not only the offset but also the slope of the pH probe.
• Connect the HI 504920 meter to HI 504910 through
the infrared interface cable.
• Immerse the pH electrode of the HI 504920 meter into the
solution measured by HI 504910, as close as possible to
the pH probe of HI 504910. Wait a few seconds for stabi-
lization.
• When the HI 504920 meter displays
the pH measurement, press TXCAL (HI
504920 must be out of the HI 504910
terminal mode).
• The LCD will display “CALt” for a couple
of seconds to indicate that the calibra-
tion of the HI 504910 transmitter is in
progress.
• If the calibration is completed correctly,
the LCD will flash the “Good” message
for a few seconds. (Also the red LED
flashes once).
