Maintenance; Preamplifier Check - Emerson ROSEMOUNT 320HP Instruction Manual

MODEL 320HP
TROUBLE
d. Span between buffers
extremely short in auto
T.C. mode.
e. Meter indication swings
widely (may swing full
scale) in AUTO T.C.
mode.
f. Sluggish, slow indica-
tion on meter for real
change in pH.
f. Electrode cannot be
standardized (STAN-
DARIZE control in
transmitter at end of
rotation).

4.4 MAINTENANCE

This section consists of replacing defective parts and making
necessary checks to determine if the sensor is operational.
The following determines if the part being checked is opera-
ble and should be used in conjunction with the
Troubleshooting Table.

4.4.1 Preamplifier Check.

To determine if the preamplifier is operable, proceed as fol-
lows:
1. Using a BNC Shorting Cap (refer to Figure 4-1) or a
paper clip, short the preamplifier connection
2. Follow analyzer instruction manual for standardization
procedure. The meter should be able to be made to read 7.0
pH.
3. If the meter/display can not be made to read 7.0 pH,
replace the old preamplifier with a new one and perform
the check again.
14
TABLE 4-1. Continued
(Troubleshooting )
CAUSE
Temperature compensator
open.
Foam junction in space.
Temperature compensator
shorted.
Glass electrode coated.
Glass electrode cracked or
coated.
Reference electrode con-
taminated.
Defective preamplifier.
Bias control in analyzer
improperly set or mistakenly
adjusted. (Model 1002,1003
only).
MAINTENANCE AND TROUBLESHOOTING
REMEDY
Check T.C. resistance (see Section
4.5.5.
Use wood junction for buffer cal.
Check T.C. resistance (see Section
4.4.5.
Clean electrode as instructed
in section 4.2.1.
Replace electrode.
Recharge and inspect per
Section 4.2.1 thru 4.2.2.
Check preamplifier as instructed
in Section 4.4.1 and replace
if defective.
Consult analyzer manual.
FIGURE 4-1. Preamplifier Check
SECTION 4.0