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Faults

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MXD70 Electrodeless Conductivity

Setup and Operating Guide

Faults

The display reads zero

 Check for open circuit sensor (conductivity or TDS modes)

 Check for damage to the connecting cable.

 Check that all input connections are secure.

 Check the sensor is wired up correctly.

 Check the sensor is immersed in the correct solution.

Instrument display appears to malfunction

 Switch the instrument power off and on again.

 Check that the display back-light is on, indicating power is reaching the unit.

 See that it displays meaningful text (Issue number etc.) in its start-up sequence, indicating

processing activity.

The Sensor Reading Is Incorrect

 Low reading due to incomplete immersion.

 There may be some trapped matter within the sensor bore.

 High conductivity readings caused by a short circuit or leakage of liquid contamination into the

sensor moulding.

 Low conductivity can be caused by accumulation of trapped air or gas coming out of solution.

Check that no "air traps" exist in the sensor installation.

 High conductivity readings caused by leakage of solution into the sensor. This usually indicates that

the sensor material has been fractured and the sensor must be replaced.

 First check that the temperature resistance is correct, otherwise the temperature compensation

circuit will cause false or erratic readings. Temporarily switching out the temperature compensation

can help to show if this is the cause of the problem.

 If another electrodeless sensor is available, this can be used to determine whether the fault lies with

the instrument or the sensor.

 Check that the sensor cable is not damaged or broken and that the outer screen does not make

contact with any other terminals or metal work.

 Check that the sensor cable is sufficiently distant from power cables or electrical noise sources.

 Check that the correct sensor type has been installed.

 Check that the correct range has been selected.

 Check that the correct sensor loop resistor calibration values have been used.

 Check that the calibration procedure has been followed precisely.

 Check that the temperature compensation has been set up as required.

 Check that the sensor cable does not exceed the maximum specified length (sensor 5m + extension

95m).

LTH Electronics MXD75 User Manual

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