33
MODEL 1181pH/ORP
SECTION 5.0
MAINTENANCE AND TROUBLESHOOTING
5.3.2 Reassembly Procedure.
1. Assemble the circuit boards and install the retain-
ing screw.
2. Align the ZERO and SPAN adjusting screws (3) on
the housing (3) to the horizontal position, slots
pointing end cap to end cap.
3. Align the ZERO and SPAN potentiometers located
on the power circuit board (5) to the horizontal posi-
tion, with blades pointing to circuit boards (4) and
(6).
4. Place circuit board assembly into housing (3) by
pushing straight in on knurled knob. Make sure
boards seat fully into terminals.
5. Install matrix cover (8 or 9), and secure with
screws and washers.
6. Inspect thread connections on housing to make
sure five undamaged threads will fully engage for
explosion proof requirements.
7. Inspect the cover O-ring (2) and replace if neces-
sary.
8. Install covers on transmitter housing (3).
9. Apply power to unit and perform appropriate cali-
bration procedure as instructed in Section 3.0.
TABLE 5-1. QUICK TROUBLESHOOTING
DIAGNOSTIC MESSAGE DESCRIPTION OF PROBLEM
REMEDY
There is no Loop
1. Voltage from power supply too
1. Correct voltage by installing proper
Current
low or missing.
resistor (See Figures 1-1, 1-2).
2. Loop Polarity is not correct.
2. Correct Loop Polarity. (see Figure
2-2).
3. Open circuit or defective
3. Repair current loop wiring or
connection in current loop wiring.
connection.
4. Jumper (W5-W6) in wrong
4. Install jumper in correct location
location (transmitter PCB).
(see Figures 3-8A and 3-8B).
5. Power PCB defective.
5. Item 6. Figure 6-1 Needs replacement.
Indication does
1. Wiring at TB2 connecting wrong.
1. Correct wiring condition, tighten
not respond to pH
Connecting loose or wiring defective.
connections or repair defective wiring.
or mV changes
2. Span and/or mid-scale switches
2. Set Switches accordingly. Refer to
not set correctly.
pH/ORP range selection. (Fig 3-1 &
3-2 location of controls).
3. Measuring electrode, preamp or
3. Perform troubleshooting procedures
electronics malfunction.
under section 5.2 of this manual.
Reading offscale,
1. Miswire
1. Verify wiring, refer to Figure 2-2, (T.C.
can’t span it in.
wires must be across TB 2-3 & TB 2-4).
2. Sensor is incompatible, has the wrong
2. Check label on sensor cable.
T.C. value.
Loop operates
1. Possible Ground Loop. Transmitter
1. Check sensor wiring to ensure that
correctly in a
has an extra ground connection
the shield wire does not touch the
beaker, but is
that is not supposed to be there.
transmitter, or sensor enclosure.
erratic or reads
2. Sensor cable may have a nick in
2. Remove sensor cable from conduit
incorrectly in the
it and makes contact with conduit,
and retest, or run a cable outside of
process.
especially if conduit has moisture
conduit.
in it (underground).
3. Power supply or distributed control
3. Remove connections to P.S. or DCS,
system causing interference.
and test loop with a bench power
4. Improper grounding of auxiliary
supply.
equipment connector to process
4. Insure all electrical devices connected
ie. pumps, mixers,valves.
to process are properly grounded.