134
Troubleshooting
Problem
Cause Solution
Meter
continuously
reads pH 14 or
drifts above 14
Open circuit in
either glass or
reference
electrode.
•
Inspect the cable and connector of the faulty electrode for evidence of a crushed
or broken cable jacket or brittleness of the cable due to exposure to heat. Discard
the electrode if damage is present.
•
Manipulate meter/electrode connections to check for intermittent continuity.
Replace if faulty.
•
Inspect the bulb, making sure it is filled with solution. If not, shake down (like a
clinical thermometer) to displace air in the pH bulb. Retest.
•
Inspect the bulb for signs of coating.
Slow response
and/or erratic
readings
Very high
impedance in either
glass or reference
electrode.
•
Inspect the pH bulb for coating or clogging. If present, clean thoroughly.
•
Keep the electrode wet at all times. If it dries out, the impedance will increase
dramatically. To restore performance, soak in 0.1 N HCI (P/N 14812-53) for 30
minutes and rinse well with distilled water.
•
Chemical degradation of pH glass can occur rapidly in a high temperature or high
pH environment, yielding sluggish response. Low temperature environments can
double the impedance for every 8 °C drop below 25 °C.
•
A high impedance electrode is extremely sensitive to electrical noise, e.g.,
oscillating electrical fields generated by motors, generators or discharges from
electrical thermostats. A free-hanging cable swinging due to air currents will also
generate erratic signals.
•
Manipulate electrode cable and connections to check for intermittent continuity.
Replace as necessary.
Ground loop
problem.
•
Check to see if the ground wire is connected properly at the pre-amp junction
box.
•
Check for continuity between the stainless steel lug on the electrode and the
ground wire at the interface.
•
Check an isolated sample. Place the probe in a beaker filled with water. If the
probe reads fine in the beaker, but not in the stream, connect the pre-amp ground
directly to the earth ground.
Temperature is
incorrect.
See “Temperature” symptom in this table.
No response to
pH change.
Cracked glass bulb.
If the electrode gives readings between 5.8 and 6.2 pH in all solutions, inspect the
glass bulb. If damaged, discard.
Short circuit.
If a constant reading of 7.0 pH or 0.0 mV is obtained, inspect the cable. If no visible
damage exists, remove the connector and test for a short circuit. Replace if faulty.
High impedance
bridge.
Inspect the connector for moisture or corrosion. If wet, rinse well with distilled water
and dry thoroughly. Determine the cause of wetness and correct it.
Temperature is
constant or
incorrect
Interface is wired
wrong.
Check interface wiring.
Thermistor is open.
Check interface wiring. Check for open at electrode RTD wire. Disconnect to make
measurement. (Should read approximately 100–110 ohms.)
Electrode won’t
calibrate
Gain or offset error.
•
Ensure that solutions are fresh and labeled properly.
•
Confirm that electrode and buffer temperatures have stabilized.
•
Confirm that the wetting cap is removed.
•
Check bulb for cracks or other damage.
•
Confirm that interface wires are connected properly.
•
Check interface connections for corrosion.
Содержание Sigma 950
Страница 2: ......
Страница 6: ...4...
Страница 20: ...18 Introduction...
Страница 34: ...32 Basic Programming Setup...
Страница 50: ...48 Sensor Installation...
Страница 82: ...80 Maintenance...
Страница 83: ...81 Appendix A Program Flow Charts Figure 22 Overview of Basic Program Menus...
Страница 84: ...82 Program Flow Charts Figure 23 Setup Flow Chart...
Страница 85: ...83 Program Flow Charts Figure 24 Options Flow Chart...
Страница 86: ...84 Program Flow Charts Figure 25 Alarms Menus Flow Chart...
Страница 87: ...85 Program Flow Charts Figure 26 Calibration Menus Flow Chart Page 1...
Страница 88: ...86 Program Flow Charts...
Страница 102: ...100 Programming Features...
Страница 106: ...104 Primary Devices Head Measurement Locations...
Страница 126: ...124 SCADA Modbus System Guidelines...