6-3
MODEL 2700 SECTION 6.0
TROUBLESHOOTING
TABLE 6-2 Quick Troubleshooting Guide
SYMPTOM ACTION
Wrong temperature reading •
Perform a Single point calibration. (Section 3.0) If cannot calibrate, sensor is bad.
Suspected temperature • Adjust the analyzer temperature to that at the sensor.
compensation problem. Insure Calibration is not beyond ± 2 Deg C of raw value.
Display pixel missing, •
Remove sensor wiring; toggle power
Display not operating correctly.
• Replace display board.
Analyzer locks up; won’t respond.
• Remove sensor wiring; toggle power.
• Check Keypad cable connection. CAUTION: Cable terminal failure can result when
removed more than 5 times.
•
Replace electronics module.
• Toggle power.
Analyzer not responding to • Verify and clean ribbon cable connection on CPU board.
key presses.
Key press gives wrong • Check Keypad cable connection. CAUTION: Cable terminal failure can result
selection. when removed more than 5 times.
• Replace keyboard front panel assy.
Wrong or no current output. • Verify: Output is not being overloaded; remove load:
(Typical voltage across unloaded output is 14-15 Vdc) Current load is not more than 600
ohms. There are no breaks in connections. Wiring is correct. Operating ranges are
set correctly Whether or not Auto Ranging function is operative
• Replace electronics module.
No backlight on display, or • Verify power wiring.
indicators. • Toggle power
Blows Fuses. • Wrong fuse. Replace with P/N 9100178
• Replace electronics module.
Drifting or unstable Readings.
•
Air bubbles in process affecting reading. Remount sensor to decrease exposure
(also see suspected Temp. to air bubbles.
Comp. problem) • Check programming of Liquid Type.
• Check programming of units of measure.
• Incorrect sensor cell constant for application.
• Verify process temperature is stable.
• Electrical or grounding interference.
• Verify sensor works in a standard solution outside of the process.
• Verify nearby water pumps motors are properly grounded.
• Verify that sensor shield never touches an Earth Ground.
• Run sensor cable through grounded metal conduit to reduce RFI effects.
Inaccurate or erroneous • Wrong sensor for measurement range.
readings. • Verify that the cell constant is correct for the measurement range
(conductivity).
• Verify Liquid Type selected (See Figure 4-2) (conductivity).
• Place sensor in known solution and check reading. If incorrect, sensor needs to be
replaced.
pH reading won’t change in
• Clean the electrode, check for cracks in the bulb.Replace electrode if
different buffers cracked. Check impedance. If zero, replace glass electrode.
pH sensor has sluggish
• Check the electrode; if still sluggish soak in 10% HCl for 1 hr.
response. Replace electrode if not rejuvenated by the HCl soak.
Will calibrate in buffers but
• Process problem or possible ground loop. Make sure that the shield wires do
not in process. NOT touch grounded metal. Disconnect output and relay connections.
6.3 TROUBLESHOOTING GUIDE
Table 6-2 lists typical symptoms that may be
encountered and suggested actions.
These are not meant to be all inclusive, but to provide a
starting point for some of the more common problems
that may occur.
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