Troubleshooting - Emerson ROSEMOUNT 320HP Instruction Manual

MODEL 320HP
4.2.3 Electrode Maintenance.
The glass electrode has a limited process life dependent on
process conditions. It is our recommendation that the elec-
trode be checked and replaced as required to insure the
proper operation of the system. Test per Figure 4.3
TROUBLE
a. Meter reads off scale.
b. Meter reads center
scale (7 pH or 0 mV)
only, will not move or
only a small distance
(± 1pH for Model 320B).
C. Indication is stable
between 3 and 6 pH,
regardless of actual
sample pH.
In a system with a stable preamplifier, many troubles listed under CAUSE may cause the meter to swing either way, depend-
ing on the electrical noise environment.
TABLE 4-1. Troubleshooting Without Advanced Diagnostics
Defective preamplifier.
Temperature compensator
shorted, with solution below
7.0 pH (in AUTO T.C. mode).
Reference and drain leads
shorted, (mis-wired) (Model 1002,
1003 only).
Broken glass electrode.
Plugged liquid junction.
Drain and source leads between
preamp and analyzer open
(broken wires) (Model 1002,
1003 only).
Broken reference electrode.
Glass or reference
lead open.
Electrodes not in solution.
Source and reference leads
shorted (mis-wired).
T.C. open or disconnected
AUTO T.C. mode.
Badly coated or internally
damaged (cracked) glass
electrode.
Glass electrode cracked.

4.3 TROUBLESHOOTING

4.3.1 Without Advanced Diagnostics.
In the event of a malfunction, refer to Table 4-1 below. This is
intended as a guide and lists the troubles in order of proba-
ble frequency of occurrence. Do not be misled by the trou-
bles; always look for the cause before trying the remedy.
CAUSE
NOTE
MAINTENANCE AND TROUBLESHOOTING
REMEDY
Check preamplifier as instructed in
Section 4.4.2 and replace if
defective.
Check T.C. resistance (see
section 4.4.6).
Correct wiring.
Replace glass electrode.
Replace liquid junction.
Correct wiring.
Replace electrode and recharge ref.
cell.
Repair wiring; check for coated
or plugged liquid junction.
Make sure flow cell is full, there
should not be any air pockets. Make
sure flow is from bottom to top of
cell.
Repair wiring.
Check T.C. per Section 4.4.5.
Clean or replace electrode.
Replace glass electrode.
SECTION 4.0
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