Metrohm 781 pH/Ion Meter - Manual (Page 127)

8 Troubleshooting – Messages – Maintenance
780/781 pH/Ion Meter, Manual
117
Message Situation Cause Remedy
limit error Direct measure-
ment, all modes Set limit for primary or sec-
ondary measured value
exceeded see Section 7.4
cal. interval
expired pH and Conc
modes Set calibration interval has
expired Recalibrate electrode (see
Section 6.2.2 and 6.5.5 )
cal.data out of
limits
pH calibration Determined calibration
data are outside limits de-
fined as calibration param-
eter Accept calibration data with
or reject them
with ; check
electrode, buffer or limits
under
6.2.2
Conc calibration • Determined slope is
outside limits of 80 –
105 % of theoretical
slope (59.16 mV per ion
charge [25°C])
• Sign incorrect for set
type of ion.
• Accept calibration data
with or reject
them with
•
Check electrode, stand-
ards under 6.5.5 or check
ion type under 6.5.2
calibration OK pH calibration,
Conc calibration
Calibration has been con-
cluded successfully Exit display with ;
this happens automatically
after 30 s; calibration data
will be accepted
manual stop Various measur-
ing runs Measurement has been
stopped manually
measuring
range exceeded Various measur-
ing runs • Electrode not immersed
in the solution
• Electrode not connect-
ed correctly
Remedy fault or change
mode
measured value
memory full Saving measured
values in a direct
measurement Attempt made to store a
further measured value
when 100 have already
been stored Delete measured values
(see
Section 7.3 )
plot data
overflow Report output Data output is faster than
printer processing speed Press and
• Increase time interval be-
tween measurements
• Increase time scale
• Reduce graph width
• Only output primary
measured value.
buffer not
defined pH calibration pH of a buffers has not
been defined under Buff-
er type: own for the
given temperature Enter missing value in tem-
perature table (see
Sec-
tion 6.2.2 )