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MW150 & MW151 Bench Meters
Expired Calibration
The instrument has a real time clock (RTC) to monitor how much time has passed since
the last pH calibration.
The RTC is reset every time the instrument is calibrated and the “expired calibration”
status is triggered when the meter detects a calibration time out. The “CAL EXPIRED” will
be displayed to warn the user that the instrument should be recalibrated.
Calibration time-out function can be set from 1 to 7 days (with 7 being default option) or
disabled (off). See Setup, pH Information for details.
For example, if a 4-day-long time out has been selected, the instrument will issue the
alarm 4 days after the last calibration.
Notes:
If the instrument is not calibrated or calibration has been cleared (with Clear
Cal option), the display will show the “NO CAL” message.
7.3. pH MEASUREMENT
Remove the electrode protective cap and submerse the tip app. 4 cm (1½”) into the
sample. pH readings are directly affected by temperature therefore, it is recommended to
wait until the sample and the pH electrode reach thermal equilibrium.
If necessary, press the RANGE/
until the display changes to the pH mode. Allow the
reading to stabilize (“ ” will turn off).
The LCD will display:
y
measured pH reading and temperature
y
temperature compensation mode (MTC - manual, ATC - automatic)
y
electrode condition (if available,
MW151
only)
y
buffers used (if enabled).
For improved accuracy make sure that the instrument is calibrated (see pH section for details).
Make sure that the electrode is kept hydrated. Rinse the probe with the sample before use. When
using the meter’s Automatic Temperature Compensation (ATC) feature, immerse the temperature
probe into the sample as close to the electrode as possible and wait for a few seconds.
Use the
keys to scroll the additional information displayed on the third LCD line:
mV offset & slope values, time of measurement, date of measurement, battery status.
