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9 SIMPLE FAULT FINDING
9.1 Error Messages
If erroneous or unexpected results are obtained the fault may
be indicated by an error message – see Table 9.1. However
some faults may cause problems with instrument calibration
when using buffer solutions or give discrepancies when
compared with independent laboratory measurements.
E
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Table 9.1 Error Messages
9.2 Calibration Fail Message or
no Response to pH/Redox Changes
The majority of problems are associated with the electrodes
and cabling. Replace the electrodes as an initial check – refer
to the appropriate instruction manual. It is also important that
all program parameters have been entered correctly and have
not been altered inadvertently – see Section 7.
If the above checks do not resolve the fault:
a) Check that the instrument responds to a millivolt input.
Connect a pH simulator, such as Model 2410, to the
transmitter input; +ve to glass and –ve to reference – see
Section 4.3 or 4.4. Select the
set the
to Redox (ORP) – see page 24.
Probe Type
Check that the transmitter displays the correct values as
set on the simulator.
Note. A normal laboratory mV source is not
suitable for use as a pH simulator.
Failure to respond to the input indicates a fault with the
transmitter which must be returned to the Company for repair.
Correct response, but with incorrect readings, usually
indicates a calibration problem. Recalibrate the transmitter as
detailed in Section 8.
P
o
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e
Set Up Parameters Page
b) Use the simulator to carry out an impedance check on the
transmitter, i.e. glass to reference, glass to earth and
reference to earth – refer to simulator manual.
If the transmitter fails this test, check for moisture within the
transmitter and in particular the terminal compartment. It is
vital that all evidence of moisture is removed with the use of a
hot air drier.
c) Reconnect the electrode cable and connect the simulator
to the electrode end of the cable. Repeat the procedures a)
c
a i
e t
d
and b) above. If the transmitter fails test b), check for
h
o
t r
moisture around the connections and check that the
insulation on the inner co-axial conductor is clean and that
the graphite layer has been removed.
m
. V
9.3 Checking the Temperature Input
Check that the instrument responds to a temperature input.
r e
u -
. p
Disconnect the PT100 leads and connect a suitable resistance
t u
box directly to the transmitter inputs – see Section 4.3 or 4.4.
Check that the transmitter displays the correct values as set on
the resistance box – see Table 9.2.
e r
c
y l t
Incorrect readings usually indicate an electrical calibration
problem – re-calibrate the instrument as detailed in Section 8.3.
T
e
m
p
e
a r
r r
e i
d
0
1
2
2
3
4
5
6
7
8
9
1
0
1
3
0
Table 9.2 Temperature Readings for Resistance Inputs
and
°C
u t
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p
t u
R
0
0
5
0
0
0
0
0
0
0
0
5 .
Ω)
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1
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0
1
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9 .
0
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7 .
9
1
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9
7 .
3
1
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6 .
7
1
1
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5 .
4
1
1
9
4 .
0
1
2
3
2 .
4
1
2
7
0 .
7
1
3
0
8 .
9
1
3
4
7 .
0
1
3
8
5 .
0
1
5
0
0 .
0
33
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