Routine Maintenance
19
despatch and should not require re-calibration. However, should re-calibration
become necessary the appropriate calibration potentiometers can be located using
the diagram below.
Ensure the equipment has been connected to the electrical supply and switched on
for at least 20 minutes. To access the PCB remove the cover plate on the right hand
side of the plinth by unscrewing the four fixing screws. It is not necessary to detach
the PCB from the plinth.
Disconnect the conductivity probe from either socket at the rear of the unit. Connect
an AC Voltmeter (Range AC mV) to pins 1 and 2 of the High conductivity socket and
adjust potentiometer VR10 on the PCB to give a reading of 50mV (RMS) on the
Voltmeter (probe excitation voltage).
Disconnect the Voltmeter then reconnect the probe to the High conductivity socket
having removed the probe from the reactor fitted to the CEXC.
High conductivity Calibration (Range 0 – 20 mS/cm)
Fill a small beaker with a Conductivity standard solution (e.g. 0.1M KCI giving a
conductivity of 12.88mS at 25°C) and measure the temperature of the standard
solution using a suitable thermometer. From the table supplied determine the actual
conductivity of the solution at the measured temperature.
Immerse the probe into the Conductivity standard solution in the beaker then adjust
potentiometer VR7 to give a reading of the standard solution in the ‘High conductivity’
window on the software to match the conductivity.
Remove the probe from the conductivity solution and rinse the probe in de-
mineralised water.
12.88 mS/cm at 25ºC 0.1 M KCl
Low conductivity Calibration (Range 0 – 5 mS/cm)
Disconnect the conductivity probe from the High conductivity socket then reconnect it
to the Low conductivity socket.
Fill a small beaker with a Conductivity standard solution (e.g. 0.01M KCI giving a
conductivity of 1.41mS at 25°C) and measure the temperature of the standard
solution using a suitable thermometer. From the table supplied determine the actual
conductivity of the solution at the measured temperature.
