How to do troubleshooting of conductivity transmitter?

The table below provides detailed guidelines for doing thorough troubleshooting of the conductivity transmitter.

What are the possible errors in conductivity measurement?

Troubleshooting of conductivity transmitter 1

Display differs from the reference measurement

Troubleshooting of conductivity transmitter 2
Possible causeSolutions
Issues with the calibrationConductivity transmitter needs to be calibrated using the instrument data sheet
Contaminated sensorClean the sensor
Inaccurate temperature measurementVerify the conductivity cell’s and the reference unit’s(thermometer) temperature values
Improper temperature compensationVerify both the method of compensation and the type of compensation
Incorrect calibration of the reference instrumentUse a calibrated instrument or calibrate the reference instrument
The conductivity sensor has a polarization errorSelect a sensor with a higher cell constant.Instead of stainless steel, use an appropriate graphite sensor (check resistance)

Troubleshooting Conductivity Analyzer Common Problems

Measured values that are unreasonable:

This include continuous measured value overflow, measured values that are always zero, measured values that are too low or high, wrong current(mA) output value or a frozen measurement value

Troubleshooting of conductivity transmitter 3
Possible causeSolutions
Moisture in the sensor or a short circuitCheck the sensor’s condition
Cable or junction box short circuitExamine the junction box and cable
Sensor interruptionCheck the sensor’s condition.
Cable or junction box interruptionExamine the junction box and cable
Incorrect setting of the cell constantCheck the instrument data sheet to confirm the cell constant setting.
Incorrectly assigned outputVerify the assignment of measured values to the transmitter’s current signals and the control system’s engineering values.
The output function is incorrect.
Verify the option of 0-20 / 4-20 mA and curve shape (linear/table).
Assembly with air cushionExamine the installation and assembly.
Grounding short in or on device
Verify the system’s grounding and insulation.
Faulty transmitter moduleUse new module for testing
Unacceptable instrument operating state (no response to key actuation)Shut down and restart the instrument
Pressure regulator and sample isolation valve could be closed. If the valve was closed, you should check its condition and then open it. and set the regulator to the appropriate setting.
Troubleshooting of conductivity transmitter 4

Conductivity Analyzer Common Problems and Troubleshooting Tips

Inaccurate measurement of temperature for the sample

Possible causeSolutions
Incorrect sensor connectionCheck that the connections are correct using the instrument loop diagram.
Cable used for cell temperature measuring is defective.Check to see whether there is an interruption, short circuit, or shunt in the cable
Type of temperature sensor that is incorrectOn the instrument, choose the type of temperature sensor.

An inaccurate conductivity measured value was obtained during the process.

Possible causeSolutions
There is no or insufficient temperature compensationAutomatic temperature compensation (ATC) chooses the type of compensation; linear or sets the correct temperature coefficient. Process temperature was set by Manual temperature compensation(MTC)
Incorrectly measuring the temperatureUtilize a thermometer or reference instrument to verify the temperature value of the sample.
Bubbles in medium Use a gas bubble trap, counter pressure (cover) to prevent the development of bubbles.
Effects of polarization (on conductive sensors only)1.Use the appropriate sensor and a larger cell constant.2. Refer the measuring range table in the technical data of the conductivity sensor.3. Replace stainless steel with graphite sensor  (and test the resistance).
High flow rate could result in bubbles.Flow should be reduced, or mount in a low-turbulence area.
Interference current in the medium (only when conductive)The ground medium in close proximity to the sensor. The most common reason for currents in the medium caused by faulty submerged motors.
Contaminated or coated sensorsSensor should be cleaned (refer the Cleaning of Conductivity Sensors  in preventive maintenance of conductivity transmitter article ). Use spray cleaning for media that are really dirty.
Incorrect field line resistance Enter the appropriate value.
Inadequate sample flow rate Keep the sample flow in the right range as instructed by the instrument’s datasheet.
Sample tubes have a leakVerify each tube connection. On the fitting side, there shouldn’t be any leaks. Additionally, no tube should be ruptured. If a leak has been identified, fix it.
The inside of sampling tubes can be chocked. Use the pressure pump to de-choke the tube or flush the system. Use pressurized fluid that is no more than 1.5 times as pressurized as the process fluid.
Adjustment of the air calibration out Verify the conductivity probe’s performance during the air calibration. The conductivity analyzer ought to display a reading of 0 for the atmosphere.
There is a problem with the transmitter calibration.Calibrate the conductivity transmitter using the reference solution.
There is a problem with the transmitter resistance calibrationCalibrate the conductivity transmitter using the decade resistance box.
Troubleshooting of conductivity transmitter 6

Fluctuations in the measured value

Possible causeSolutions
Measuring cable interferenceAccording to the connection diagram, connect the cable screen.
Interference in the signal output lineEnsure that the line routing is correct.Consider using separate line routing.Signal output and measurement input lines should be routed separately.
Interference currents in the medium Getting rid of any interference sources or nearby ground mediums
Incorrect setup of the damping value If the variations are extremely large, increase the dampening factor value of the conductivity analyzer.
The rate of sample flow is not constant.Follow the vendor manual’s sample flow to the conductivity analyzer. The sample flow shouldn’t have air bubbles either.
There are leaks in the sample tube.The conductivity reading will fluctuate as a result of minor tube leaking.  So arrest the leak.
Troubleshooting of conductivity transmitter 6

No current output signal for conductivity 

Possible causeSolutions
Open or short-circuited line Disconnect the wire and use a multimeter to measure the instrument directly (4 to 20 mA). 
Defective Current(mA) Output Module
It is recommended that you either repair or replace the module. 
Troubleshooting of conductivity transmitter 7

Current conductivity output signal with a fixed conductivity.

Possible causeSolutions
Active simulation at the momentTurn off the simulation.
processing system functioning in an inappropriate ways Shut down and restart the instrument. If the issue persists, check the installation, screen, and grounding. 

Current(mA) output signal that is incorrect

Possible causeSolutions
mA Current assignment is incorrect.Check the current assignment; it can be 0-20 mA or 4-20 mA. 
Excessive total load in the current loop (>500).Disconnect the output and use a multimeter to measure the mA directly on the instrument.
Issue with electromagnetic compatibility (EMC)Directly measure on the instrument after disconnecting both output lines.
Use shielded lines, ground screens on both sides, and if necessary, route the line via another duct.

No or a dark display

Possible causeSolutions
Insufficient line voltageUse a multimeter to check the supply voltage; it should be within the manufacturer’s suggested range.
Incorrect or too low supply voltage Compare the name plate data and the actual line voltage.
Improper connection Not properly tightened at the terminal.Insulation was stuck.Utilized incorrect terminals.
Faulty device fuseReplace the fuse by comparing the nameplate information with the line voltage.
Faulty power supply card or unitReplace the unit or the power supply card  

Mismatch between field and PLC/DCS conductivity values

Possible causeSolutions
Inaccurate field and PLC/DCS range configurationVerify both sides of the range. and make sure they are identical to the instrument data sheet.
There is a force present in either the field conductivity transmitter or the PLC/DCS. Remove force after carrying out the correct process for restoring force.

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