YOKOGAWA FC400G

< 9. Troubleshooting >
9-4
IM 12F5A1-01E
9.2 FortheCaseWhereNoErrorIndicationAppears
Therearecaseswherenormalmeasurementisprevented,suchasinuctuatingsetvalueeven
though no error is detected. Table 9.2 shows such abnormalities, possible causes, and remedies.
Table9.2 Abnormalities,TheirPossibleCauses,andRemedies
Abnormalities PossibleCauses Remedies
Measured value is
abnormal.
1. Indicator electrode has stopped.
a. Electrode drive belt does not turn.
b. Cell motor does not run.
2. Indicator electrode has worn out.
3.Insu󰀩cientcontinuityattheelectrode
mechanism block.
1. Take steps as follows :
a.Su󰀩cientlytightenthesetscrew.
b. Replace the motor with a new one.
2. Replace the electrode with a new one.
3. Replace the rotating contact (see Sec.
8.2.1).
Measurement error
is large.
1. Indicator electrode has been
contaminated.
2.Zeroand/orspanhasnotbeen
correctlyadjusted.
3. Auto zero calibration abnormal.
1. Polish the indicator electrode in
accordancewithSec.8.1.1also,clean
the ceramic beads in accordance
withSec.8.1.2(ifitisnotpossibleto
su󰀩cientlycleanthebeads,replace
them with new ones).
2. Conduct zero and / or span calibration.
3a.Replaceactivatedcharcoallter
3b. Piping related to auto zero calibration
is blocked
Measured value
uctuateslargely.
1. Indicator electrode does not rotate at
constant speed.
2.Insu󰀩cientcontinuityattheelectrode
mechanism block
1. Check if the set screws have loosened.
Check if the belt, driven shaft assembly
is normal.
If not, replace them.
2. Replace the rotating contact.
Measured value
does not vary.
1. Measuring tank has no sample
water.
2. Electrode to electrode circuit is open.
3. No voltage is applied between the
indicator and counter electrodes.
1. Repair abnormality such as piping
disconnection or sample water feed
failure to normal condition
2. Repair open circuit. If open circuit
occurs in an electrode, replace such
electrode.
3. Check the converter.
Abnormal analog
output
1. Lead resistance is too large.
2. Output circuit abnormal.
1.Reducetheresistanceto550Ωorless.
2. Contact YOKOGAWA.
The reading
deviatessignicantly
in the positive
(or negative)
direction, or
overshoot occurs.
1. Span calibration has not been
performed correctly. Span calibration
was performed with electrode
sensitivity initialization set to ON (1)
inservicecode08("CHANG"Mode)
and using a calibration solution with
alargedi󰀨erenceinconcentration
from the input concentration value.
1. Set electrode sensitivity initialization to
ON(1)inservicecode08("CHANG"
Mode) and perform calibration again.
(See item (f) in Sec. 5.4.2, Sec. 7.3)