Liquisys M CPM223/253 Maintenance
Endress+Hauser 91
8.1.6 Connecting lines and junction boxes
Check the cables and connections for moisture. Moisture is indicated by a sensor slope that
is too small. If no more display is possible or if the display is fixed at pH 7, please check the
following components:
•Sensor head
• Sensor connector
•pH measuring cable
• Junction box, if fitted
•Extension cable
Faulty measurement due to moisture in the measuring cable
‣ If there is moisture in the measuring cable, the cable must be replaced!
A shunt in the cable of > 20 M can no longer be measured with normal multimeters but is
damaging for the pH measurement. A reliable test can be carried out with a usual
commercial insulation meter:
• Make sure to disconnect the pH measuring cable from the sensor and device!
• If you are using a junction box, check the infeed and outfeed measuring cable separately.
• Check the cable with 1000 V DC (at least with 500 V DC) testing voltage.
• If the cable is intact, the insulation resistance > 100 G.
• If the cable is defective (moist), there is flashover.
The cable must be replaced.
The sensor head and junction box can be cleaned and dried with a hot air dryer.
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