The table below provides detailed guidelines for doing thorough troubleshooting of the conductivity transmitter.
What are the possible errors in conductivity measurement?
Display differs from the reference measurement
|Issues with the calibration
|Conductivity transmitter needs to be calibrated using the instrument data sheet
|Clean the sensor
|Inaccurate temperature measurement
|Verify the conductivity cell’s and the reference unit’s(thermometer) temperature values
|Improper temperature compensation
|Verify both the method of compensation and the type of compensation
|Incorrect calibration of the reference instrument
|Use a calibrated instrument or calibrate the reference instrument
|The conductivity sensor has a polarization error
|Select 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
|Moisture in the sensor or a short circuit
|Check the sensor’s condition
|Cable or junction box short circuit
|Examine the junction box and cable
|Check the sensor’s condition.
|Cable or junction box interruption
|Examine the junction box and cable
|Incorrect setting of the cell constant
|Check the instrument data sheet to confirm the cell constant setting.
|Incorrectly assigned output
|Verify 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 cushion
|Examine the installation and assembly.
|Grounding short in or on device
|Verify the system’s grounding and insulation.
|Faulty transmitter module
|Use 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.
Conductivity Analyzer Common Problems and Troubleshooting Tips
Inaccurate measurement of temperature for the sample
|Incorrect sensor connection
|Check 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 incorrect
|On the instrument, choose the type of temperature sensor.
An inaccurate conductivity measured value was obtained during the process.
|There is no or insufficient temperature compensation
|Automatic 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 temperature
|Utilize 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 sensors
|Sensor 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 leak
|Verify 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 calibration
|Calibrate the conductivity transmitter using the decade resistance box.
Fluctuations in the measured value
|Measuring cable interference
|According to the connection diagram, connect the cable screen.
|Interference in the signal output line
|Ensure 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.
No current output signal for conductivity
|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.
Current conductivity output signal with a fixed conductivity.
|Active simulation at the moment
|Turn 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
|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
|Insufficient line voltage
|Use 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.
|Not properly tightened at the terminal.Insulation was stuck.Utilized incorrect terminals.
|Faulty device fuse
|Replace the fuse by comparing the nameplate information with the line voltage.
|Faulty power supply card or unit
|Replace the unit or the power supply card
Mismatch between field and PLC/DCS conductivity values
|Inaccurate field and PLC/DCS range configuration
|Verify 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.