Maintenance Liquisys M CUM223/253
84 Endress+Hauser
8.1.2 Checking the measuring point
The sensors CUS31 and CUS41 cannot be simulated as they contain the complete data
processing and all the measured values are transmitted to CUM223/253 using the digital
interface RS 485. Therefore a functional sensor is required for the measuring point test.
Method for testing a measuring point:
• Check that device is operable and that the display reacts appropriately, e.g. by pressing the
PLUS key.
• Check the current outputs by carrying out a current simulation (Field O3(2)).
• Measure the sensor operating voltage: approx. 10 to 16 V at terminals 87 (+) and 88 (–).
• The cause for an incorrect voltage may be present either at the device or at the sensor.
– Replace the sensor.
– If the sensor operating voltage is still too low replace the power supply module LSGA/
LSGD (Pos. 10/20, make sure to use the appropriate version - see spare parts).
• Sensor operating voltage is o.k. but no measured turbidity value even with a new sensor.
Replace the transmitter module MKT1.
8.1.3 Replacing the sensor
The sensors CUS31/CUS41 contain their own digital signal processor and communicate with
the turbidity measuring instrument via an interface RS 485. All sensor data (factory
calibration data and customer calibration data) are permanently saved in the sensor.
You can find detailed information on these sensors in the:
• Operating Instructions Turbimax W CUS31 BA00176C/07/EN.
• Technical Information Turbimax W CUS41 TI00177C/07/EN.
When replacing a sensor pay attention to the following:
• Replacing the sensor CUS31-xxA or CUS41
All calibration data are saved in the sensor. When using the original data records (“read
only”), no calibration is necessary after sensor replacement. Medium-specific calibrations
must be repeated.
• Replacing the sensor CUS31-xxE or CUS31-xxS
All factory calibration data are saved in the sensor. The sensor and the assembly are
calibrated together. No additional calibration is required for applications with pure or
ultrapure water, if the sensor and the assembly are replaced together. The calibration data
of the sensor are automatically transferred to the measuring instrument.
8.1.4 Maintenance assembly
Please refer to the corresponding assembly Operating Instructions for information on
maintaining and trouble-shooting the assembly. Here you can find a description for
assembling and disassembling, sensor replacement, seal replacement, as well as
information on stability and spare parts and accessories.
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