Xylem CG 839 - Manual (Page 5)

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1 Description
The Microprocessor pH Meter CG 839 can be used to make pH-value, redox voltage and temperature
measurements. The measured temperature is shown in the display parallel to the pH or mV value.
The calibration data for pH measurements are preserved when the Microprocessor pH Meter CG 839 is
switched off.
For adjustment to match the electrode function, the data for three buffer solutions, including their
temperature characteristics, are stored in the Microprocessor pH Meter CG 839.
2 Commissioning
The Microprocessor pH Meter CG 839 is delivered ready for operation. A warning appears in good time in
the display when the batteries are nearly exhausted.
Connect the electrode type no. N 2042 A combination electrode with integrated temperature sensor
(resistance thermometer Pt 1000).
Switch-on the Microprocessor pH -Meter CG 839: Hold the - key, the - key or the - key
depressed until the message <> appears in the upper left corner of the display. The
Microprocessor pH Meter CG 839 is ready to measure, when <> disappears.
3 Calibration of the Microprocessor pH Meter CG 839 ("Calibrate")
The simplest procedure is to use a combination pH-electrode with integrated temperature sensor, e. g.
type no. N 2042 A. The buffer solutions whose data are stored in the Microprocessor pH Meter CG 839
have the following pH-values at 25 °C: pH = 4.00, pH = 7.00, and pH = 10.00. The call-up sequence of the
buffer solutions is arbitrary.
Dip the electrode into the first buffer solution used and press the corresponding -key. The messages
<>, <>, <> and the corresponding pH-value appear in the display. <> flashes
when the buffer solution has been identified and disappears when the reading has become stable. The
message <> flashes as request to continue the calibration procedure.
Rinse the electrode with distilled water and then repeat the procedure with the second buffer solution. The
corresponding indication is <>. Actual temperature differences of the buffer solutions are
automatically normalized to 25 °C.
When the Microprocessor pH Meter CG 839 has automatically taken-over the calibration, the messages
<> and <> appear in the display, and then the electrode zero-point pH-value and the slope in
%. The Microprocessor pH Meter CG 839 with electrode is now ready for making measurements. To
display the slope and zero-point again, press one of the - keys and thereafter the - key.
4 Single-point calibration
A simplified calibration can be made as described under chapter 3 "Calibration of the Microprocessor
pH Meter CG 839" with only one buffer solution. When the flashing message <> appears in the
display, terminate the calibration procedure by pressing the - key. This single-point calibration
corrects the electrode zero-point and keeps the slope value from the previous full calibration.
5 pH-measurement with combination pH-electrode
type no. N 2042 A (with integrated temperature sensor Pt 1000)
Press the - key to switch to the <>- function. The function displays <> and <<°C auto>>
light up.
Dip the electrode into the sample solution. The temperature-compensated pH-value reading appears in
the display after elapse of an adequate temperature equilibration time.