pH
pH reading does not match independent pH meter measurement
1. Recalibrate pH.
2. Clean the pH electrode.
3. Recalibration can be performed at a single point (“grab cal”) or at two points using known pH buff ers.
4. If the pH being displayed is dramatically incorrect or fl uctuating drastically and cannot be corrected,
check all pH electrode cable connections as well as the cable
connector at the electrode
. If all
connections are verifi ed and the problem cannot be corrected through through cleaning and/or a two-
point calibration, replace the pH electrode.
5. If the raw pH sensor mV values are outside the acceptable ranges then replace the pH probe.
ORP
ORP reading does not match independent ORP measurement
1. Recalibrate ORP electrode.
2, Clean the ORP electode.
3. If the ORP being displayed is dramatically incorrect or fl uctuating drastically and cannot be corrected,
check all ORP cable connections as well as the cable
connector
at the electrode. If all connections
are verifi ed and the problem cannot be corrected through cleaning and/or recalibration, replace the
ORP electrode.
Conductivity
Conductivity reading does not match independent conductivity meter measurement
1. Recalibrate conductivity electrode.
2. Clean the conductivity electrode.
3. If the conductivity being displayed is dramatically incorrect or fl uctuating drastically and cannot be
corrected, check all conductivity cable connections as well as the cable
connector
to the electrode.
If all connections are verifi ed and the problem cannot be corrected through cleaning and/or
recalibration, replace the conductivity electrode.
Display and Circuit Board
Display is blank
1. Verify the power is turned on to the unit.
2. If it is, check the DC voltage to the monitor circuit board on Modbus terminal connections V- and V+.
Refer to Figure 9.
3. A blank display may indicate a failure of the display, the power supply board or the primary circuit
board. Consult Hydro Instruments or an authorized representative for assistance.
4-20 mA Output channel values are not accurate
1. Verify the output selection is correct. For example, if the output signal for a pH electrode is measuring
something other than 12mA at 7.00 pH, verify that the output you are measuring is confi gured to “pH”.
2. Check the output calibrations at 4mA and 20mA by accessing the appropriate output channel
calibration as detailed in Figure 7B.
NOTE: The output calibration numbers from the factory calibration are recorded on the inside of the
electronics enclosure for future reference.
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