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terminal strip (refer to Figure 7). Make sure that the correct colors go to the correct terminals, and that the connections
are tight. Restore power and see if the conductivity is back to normal. If not, replace the electrode.
8.4 Procedure for evaluation of the pH/ORP electrode
The most common cause of a calibration failure is an electrode problem. First try cleaning the electrode, then retry
the calibration. If this fails again, replace the electrode and retry the calibration.
The next most common problem is wet or poor connections. Check the connection of the electrode to the cable for
moisture. Check the connections between the cable and the terminal strip. Make sure that they are tight, that the
terminal is not clamped to the plastic jacket, and that the wires are routed to the correct terminal. If there is a junction
box installed between the electrode and the controller, check the wiring there as well.
You should be able to measure the +5VDC ±5% and -5VDC ±5% vs IN- at the terminal strip. If not, the controller is
faulty. You should be able to measure the IN+ vs IN- (DC scale) and get the appropriate values for the buffer solu
-
tions used. If not, the preamplifier or its wiring is faulty.
The last possibility is to try replacing the preamplifier.
8.5 Diagnostic Lights
Some of the circuit boards inside the controller have diagnostic lights.
CONTROLLER BOARD D1 LED
Indicates status of the software application. Normal operation is that 5 seconds after power-up, it does one long blink on, two short
blinks, on long blink off. If it is not doing this:
Possible Cause
Correction Action
Controller software is not running
Try a power cycle to reset it
Faulty controller board
Replace controller board
CONTROLLER BOARD D3 LED
Indicates the status of the 5 VDC power supply. Normal operation is ON. If not on:
Possible Cause
Correction Action
Faulty ribbon cable
Replace ribbon cable
Faulty power supply
Replace power/relay board
CONTROLLER BOARD D2 LED
Indicates the status of the 3.3 VDC power supply. Normal operation is ON. If not on:
Possible Cause
Correction Action
Faulty ribbon cable
Replace ribbon cable
Faulty power supply
Replace power/relay board
SENSOR BOARD LED
Indicates the status of the sensor board. Blinks slowly for several seconds during power-up. Normal operation is OFF. If not behaving
this way:
Possible Cause
Correction Action
Sensor card locked up
Try a power cycle to reset it
Sensor card not seated correctly
Unplug the card and plug it back in
Faulty sensor card
Replace sensor card
ETHERNET BOARD LED
Indicates status of the software application. Normal operation is that 5 seconds after power-up, it cycles 5 seconds on, 5 seconds off. If
not behaving this way:
Possible Cause
Correction Action
Network software is not running
Try a power cycle to reset it
Network software file system is corrupt
Go to Config – File Utilities and Repair Network
File System
Ethernet card not seated correctly
Unplug the card and plug it back in
Faulty Ethernet board
Replace Ethernet board
