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< 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 fluctuating 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. Insufficient continuity at the electrode
mechanism block.
1. Take steps as follows :
a. Sufficiently 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
sufficiently clean the beads, replace
them with new ones).
2. Conduct zero and / or span calibration.
3a. Replace activated charcoal filter
3b. Piping related to auto zero calibration
is blocked
Measured value
fluctuates largely.
1. Indicator electrode does not rotate at
constant speed.
2. Insufficient 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 significantly
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 difference 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)