User Guide

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

secondary LCD displays