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Display Condition Suggested SolutionsPossible Causes
"- - - -"
Value Must be less
than 3
Value must be greater than 0
"Value must be
400 or less"
Display erratic, shows "0" or
"------" intermittently
"Too much Error
Check Sensor"
Display is over range. This may be a
normal condition if your process operates
at/near the limits of the sensor range.
kΩ or MΩ units selected & sensor is open.
The PPM factor must be a value from
0.00 to 3.00
Custom cell constant cannot be set to 0
Pulse Rate cannot be greater than 400
Auxiliary Power not connected
Defective or dirty/coated sensor
Wiring error
Fluid conductivity too low
Defective temp element
Check sensor for correct range.
Check Decimal setting in OPTIONS menu.
Check Calibrate menu settings for incompatible
SOURCE and RANGE values.
Set a PPM value less than 3.
Set cell constant to a value greater than 0
set a pulse rate value less than 400
Connect Auxiliary power
Clean or replace sensor
Check and correct wiring
Replace sensor
Troubleshooting
Parts Per Million (PPM) Factor
This feature is only applicable when PPM display units are selected. The programmable PPM Factor is adjustable from 0.01 to
3.00 (factory default = 2.00). Determine the best PPM Factor for a process solution by calculating the solution's conductivity (µS)
and the percent of total dissolved solids (PPM).
PPM Factor =
Solution conductivity (µS)/cm
Total dissolved solids (PPM)
TDS (PPM) =
Solution conductivity (µS)/cm
PPM Factor
Example: • Solution conductivity = 400 µS/cm
• TDS = 200 PPM (mg/L)
PPM Factor =
400 µS/cm
= 2.00
200 PPM
If a Current Loop is locked at 3.6 mA, the problem is related to the temperature circuit:
This occurs only if the CDTX-90 detects a resistance from the temperature sensor that is less than 250Ω or greater than 2800Ω.
• Check the sensor wiring for open/short or poor connections on white (TEMP IN) and black (ISO GND)wires.
• The PT1000 temperature device in the sensor is defective.
• The transmitter is defective.
Auxiliary Power (terminals 1 and 2) must ALWAYS be connected for the CDTX-90 to operate.
Technical notes