Endress+Hauser Liquiline M CM42 User manual

Products Solutions Services
CM42-MAA101EBE00
BA00382C/07/EN/16.16
Valid as of:
Firmwareversion 02.02.00
Operating Instructions
Liquiline M CM42
Two-wire transmitter for pH/ORP measurement
with Memosens glass sensors
Part 2

Endress+Hauser
CM42-MAA101EBE00
Table of contents
1 Operation via the fieldbus . . . . 4
2 Calibration and adjustment . . . 5
2.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Notes on the calibration . . . . . . . . . . . . . . 8
2.4 Calibration intervals . . . . . . . . . . . . . . . . . 8
2.5 Types of calibration . . . . . . . . . . . . . . . . . 10
2.6 Two-point calibration . . . . . . . . . . . . . . . 10
2.7 Single-point calibration . . . . . . . . . . . . . 11
2.8 Temperature adjustment . . . . . . . . . . . . 12
2.9 Calibrate . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3 Diagnostics, troubleshooting . 14
3.1 General troubleshooting . . . . . . . . . . . . . 14
3.2 Diagnostic information on local display 18
3.3 Diagnostic information via fieldbus . . . 22
3.4 Adapting the diagnostic information . . 22
3.5 Pending diagnostic messages . . . . . . . . . 23
3.6 Diagnostic list . . . . . . . . . . . . . . . . . . . . . . 23
3.7 Logbooks . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.8 Simulation, Resetting the measuring device
24
3.9 Change sensor . . . . . . . . . . . . . . . . . . . . . 26
3.10 Sensor type change . . . . . . . . . . . . . . . . . 27
3.11 Sensor status . . . . . . . . . . . . . . . . . . . . . . 28
3.12 Output state . . . . . . . . . . . . . . . . . . . . . . . 29
3.13 Device information . . . . . . . . . . . . . . . . . 29
3.14 Sensor information . . . . . . . . . . . . . . . . . 29
3.15 Firmware history . . . . . . . . . . . . . . . . . . . 30
4 Maintenance. . . . . . . . . . . . . . . 31
5 Repair. . . . . . . . . . . . . . . . . . . . . 32
5.1 Spare parts . . . . . . . . . . . . . . . . . . . . . . . . 32
5.2 Replacing modules . . . . . . . . . . . . . . . . . . 34
5.3 Return . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.4 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
6 Accessories . . . . . . . . . . . . . . . . 35
6.1 Installation kits . . . . . . . . . . . . . . . . . . . . 36
6.2 Weather protection . . . . . . . . . . . . . . . . . 36
6.3 Firmware update and upgrade . . . . . . . . 36
6.4 Data management . . . . . . . . . . . . . . . . . . 36
6.5 Measured value simulation . . . . . . . . . . . 37
6.6 Communication-specific accessories . . . 37
7 Technical data. . . . . . . . . . . . . . 38
7.1 Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.2 Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.3 Protocol-specific data . . . . . . . . . . . . . . . . 39
7.4 Electrical connection . . . . . . . . . . . . . . . . 40
7.5 Performance characteristics . . . . . . . . . . 41
7.6 Environment . . . . . . . . . . . . . . . . . . . . . . . 42
7.7 Mechanical construction . . . . . . . . . . . . . 42
Index. . . . . . . . . . . . . . . . . . . . . . 43

Operation via the fieldbus CM42-MAA101EBE00
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1 Operation via the fieldbus
The device supports HART communication via current output 1. Here, digital data are
transmitted in addition to the current. Most process control systems have HART inputs that can
process the data further directly. Process values, the status of the process values and the device
status are transmitted.
The device can also be configured via HART. The device driver enables access to the complete
Setup and Diagnostics menu with few exceptions.
You have the following options for configuration:
• The process control system directly supports the use of DDs (Device Descriptions) and DTMs
(Device Type Managers) or
• you use an additional HART master, e.g. a handheld terminal or FieldCare in conjunction with
a modem.
The interface offered by the DDs and DTMs largely corresponds to the menu structure of local
operation.
It is not possible to access all the tables and the calibration with DDs or DTMs. In addition, it is
not possible to access the logbooks with a handheld terminal.
A detailed description of the commands and features supported by the device is provided in
SD01325C under "Document/Manuals/Software" and then "Special Documentation (SD)" on
www.endress.com/cm42.

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2 Calibration and adjustment
The calibration provides important information on the condition of your sensor and the
quality of the pH measurement.
pH glass electrodes
In addition to the slope that has an ideal value of approx. -59 mV/pH at 25 °C, the change in the
zero point also provides important information to the user. It is an indicator of the condition of
the gel-like layer of the pH glass and could point to a blockage in the reference system. Suitable
maintenance would involve cleaning or regenerating the sensor.
To perform a quick test, simply immerse the sensor in a buffer solution with the same pH value
as the internal buffer (e.g. pH 7). 0 mV would be an ideal value. The greater the deviation from
the ideal value, the poorer the condition of the sensor (±20 mV is still acceptable in most
situations).
2.1 Definitions
Calibration (as per DIN 1319):
A calibration is defined as a set of operations that establish the relationship between the
measured value or expected value of the output variable and the related true or correct value of
the measured variable (input variable) for a measuring system under specified conditions.
A calibration does not alter the performance of the measuring device.
Adjustment
An adjustment corrects the value displayed by a measuring device, in other words the
measured/displayed value (the actual value) is corrected so that the reading agrees with the
correct, set value.
The value determined during calibration is used to calculate the correct measured value and
saved in the sensor.
2.2 Terminology
2.2.1 Zero point and slope
Using a mathematical function, the transmitter converts the input signal of the sensor y (raw
measured value) to the measured value x. In many cases, this function is a simple linear of the
form y = a + b .x.
The linear element "a" is usually equivalent to the zero point and the factor "b" is the slope of the
line and is often known as the sensor slope.

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The Nernst equation, which is used to calculate the pH value, is a typical linear relationship:
pH = -lg(aH+), aH+ ... activity of the hydrogen ions
Ui... raw measured value in mV
U0... zero point (=voltage at pH 7)
R ... universal gas constant (8.3143 J/molK)
T ... temperature [K]
F ... Faraday constant (26.803 Ah/mol)
The slope of the Nernst equation (-2.303RT/F) is known as the Nernst factor and has the
value -59.16 mV/pH at 25 °C.
2.2.2 Delta slope
The device determines the difference in the slope between the calibration that is currently valid
and the last calibration. Depending on the sensor type, this difference is an indicator of the
condition of the sensor. The smaller the slope, the less sensitive the measurement, and the
accuracy deteriorates particularly in the low measuring range.
Depending on the operating conditions, users can define limit values that represent the still
tolerable absolute values of the slope and/or slope differentials. If the limit values are exceeded,
maintenance must be performed on the sensor at the very least. The sensor must be replaced if
the insensitivity problems persist after maintenance has been carried out.
a0013593
Fig. 1: Linear function
aZeropoint
bSlope
U=U
i0
-2.303 RT
FpH

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2.2.3 Delta zeropnt.
The device determines the difference between the zero points of the last and second-last
calibration. A shift in the zero point does not alter the sensitivity of the measurement. However,
if the offset is not corrected this can falsify the measured value.
As with the slope, you can also define and monitor limit values for the offset. If the limit values
are exceeded, this means that maintenance must be performed on the sensor.
a0013594
Fig. 2: Delta slope
Blue Last calibration
Red Calibration currently valid
 bDeltaslope
a0013595
Fig. 3: Delta zeropnt.
a1 Zero point of the second-last calibration
a2 Zero point of the last calibration
 aDeltazeropnt.

Calibration and adjustment CM42-MAA101EBE00
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2.3 Notes on the calibration
The following rules apply for all parameters:
• Calibrate in a way that reflects conditions in the process.
– If the process medium is constantly moving, also move the calibration solution accordingly
(e.g. use a magnetic stirrer if calibrating in the laboratory).
– If your medium is relatively stationary, calibrate in solutions that are also stationary.
• Make sure that the samples are homogeneous for reference measurements, sample
calibration etc.
• Use the same menu settings as those in the process to perform the calibration.
Example: If you automatically compensate for the temperature effect during pH
measurement, switch on automatic temperature compensation for the calibration also.
It is advisable to perform the laboratory calibration using the "Memobase Plus" database
soware (→"Accessories"). This improves the availability of your measuring points and all
the calibration and sensor data records are stored securely in the database.
2.4 Calibration intervals
2.4.1 Specifying the intervals
The service life of a pH glass electrode is limited. This is due, in part, to the deterioration and
aging of the pH-sensitive membrane glass. This aging causes the gel-like layer to change and
become thicker over time.
Symptoms of aging include:
• Higher membrane resistance
• Slow response
• Decrease in the slope
A change in the reference system (e.g. due to contamination, i.e. unwanted redox reactions at
the reference electrode) or electrolyte solution dissolving away in the reference half cell can
change the reference potential, which, in turn, causes a zero point shift in the measuring
electrode.
To ensure a high level of accuracy, it is important to readjust the pH sensors at set intervals.
The calibration interval depends heavily on the area of application of the sensor, as well as the
required level of accuracy and reproducibility. The calibration interval can vary between daily
and once every few months.
Defining the calibration interval for the process
1. Check the sensor with a buffer solution, e.g. pH 7.
Proceed as specified in Step 2 only if the value deviates from the set point. No
calibration/adjustment is necessary if the value is within the defined deviation tolerance
range (see the Technical Information for the sensor).
2. Calibrate and adjust the sensor.

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3. After 24 hours, check again with the buffer solution.
• If the deviation is within the permitted tolerance range, increase the checking interval
by doubling it for example.
• If the deviation is larger, you must shorten the interval.
4. Continue to proceed as defined in Steps 2 and 3 until you have identified the suitable
interval.
Monitoring the calibration
‣Define the limit values for monitoring the slope and zero point differentials (SETUP/Sensor
pH/ORP/Sensor diagnostics/Diagnostic limits).
These limit values depend on the process and must be determined by empirical means.
During calibration a diagnostics message is displayed if the defined warning limits have been
exceeded. You then have to service the sensor by cleaning the sensor or reference, or by
regenerating the glass membrane.
You have to replace the sensor if warning messages continue to be displayed despite the
maintenance measure.
2.4.2 Monitoring the calibration interval
If you have established calibration intervals for your process, you can also have the device
monitor them.
Two functions are available to monitor the calibration interval:
1. Calibration timer (SETUP/Sensor pH/ORP/Sensor diagnostics/Diagnostic limits/Calibration
timer)
You specify the calibration interval and the controller generates a diagnostics message
once the set time has elapsed. You then recalibrate the sensor or replace it with a
precalibrated sensor.
The timer is reset with the new calibration.
2. Calibration validity (SETUP/Sensor pH/ORP/Sensor diagnostics/Diagnostic
limits/Calibration expired)
You set time limits to specify how long a calibration should be regarded as valid.
Memosens sensors save all the calibration data. In this way it is easy to see whether the
last calibration took place in the specified timeframe and is therefore still valid. This is
particularly advantageous when working with precalibrated sensors.

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2.5 Types of calibration
2.5.1 pH measurement
The following types of calibration are possible:
• Two-point calibration
– With calibration buffers
– Entry of data for the slope, zero point and temperature
• Single-point calibration
– Entry of a reference value
– Sample calibration with laboratory comparative value
• Temperature adjustment by entering a reference value
If using a combined sensor (CPS16D/CPS76D/CPS96D) you must calibrate both the pH
electrode and the ORP electrode to get reliable rH values, for example.
2.5.2 Measuring the ORP
The following types of calibration are possible:
• Two-point calibration with medium samples (only ORP %)
• Single-point calibration with calibration buffer (only ORP mV)
• Data entry of an offset (only ORP mV)
• Temperature adjustment via reference value
2.6 Two-point calibration
2.6.1 General information
Two-point calibration is the preferred method for pH sensors, particularly in the following
applications:
• Municipal and industrial wastewater
• Natural waters and drinking water
• Boiler feedwater and condensates
• Beverages
Calibrating with buffers with pH 7.0 and 4.0 is recommended for most applications.
Alkaline buffer solutions have the disadvantage that carbon dioxide from the air can alter the
pH value of the buffer on the long term. If calibrating with alkaline buffers it is best to do so in
closed systems, such as flow assemblies or retractable assemblies with a rinse chamber, to
minimize the effect of air.
2.6.2 With calibration buffers
pH measurement
You use calibration buffers to perform two-point calibration. The quality buffers supplied
by Endress+Hauser are certified and measured in an accredited laboratory. The

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accreditation (DAR registration number "DKD-K-52701") confirms that the actual values and the
maximum deviations are correct and traceable.
To calibrate the sensor, remove it from the medium and calibrate it in the laboratory. Since
Memosens sensors save the data, you can always work with "precalibrated" sensors and do not
have to stop monitoring the process to perform a calibration.
Only use calibration buffers once.
Measurement of the ORP in % (2-point cal.)
To obtain useful ORP % values, you must adapt the sensor to your process. This is achieved
through two-point calibration. The two calibration points are characteristic of the most
important states your medium can assume in the process.
You require two different compositions of your medium that represent the characteristic limits
of your process (e.g. 20% and 80% value).
The absolute value in mV is not relevant for the ORP % measurement.
Measuring the ORP in % (data entry)
As an alternative to two-point calibration with medium samples, you can also define the two
calibration points via data entry. To do so, use data pairs in mV and % for the two calibration
points that represent the most important states of your process medium. Ideally, you will have
determined the mV values with a reference measurement.
2.6.3 Entering data for the zero point, slope and temperature(only pH)
You enter the slope, zero point and temperature manually. The function for determining the pH
value is calculated from these values. Thus, the data entry returns the same result as two-point
calibration.
‣You must determine the slope, zero point and temperature alternatively.
2.7 Single-point calibration
2.7.1 Numeric input of a reference value (1-point cal.)
pH measurement
Single-point calibration is particularly useful if the deviation of the pH value from a reference
value, and not the absolute pH value itself, is of interest to the user. Applications for single-point
calibration include:
• Process control
• Quality assurance

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Fluctuations in the process value should not exceed ±0.5 pH and the process temperature must
remain relatively constant. As the measuring range is limited as a result, it is possible to set the
slope to -59 mV/pH (at 25 °C).
Alternatively, you can also use the "sample calibration". Here, you take a sample from the process
and determine the pH value in the laboratory. In the case of the laboratory sample, you must
make sure that the pH value is determined at the process temperature.
Measuring the ORP in mV
You enter the offset directly with this type of calibration. Use the measured value of a reference
measurement, for example, to determine the offset.
2.7.2 Sample calibration (grab sample cal., only pH)
With this type of calibration, you take a sample of the medium and determine its pH value (at
process temperature) in the laboratory. You then use this laboratory value to adjust the sensor.
This does not change the slope of the calibration function.
2.7.3 With ORP buffers (only measurement of the ORP)
With this type of calibration, you work with calibration buffers, e.g. ORP buffers from
Endress+Hauser.
For this purpose, you remove the sensor from the medium and calibrate it in the laboratory.
Since Memosens sensors save the data, you can always work with "precalibrated" sensors and do
not have to stop monitoring the process for extended periods to perform a calibration.
Only use calibration buffers once.
2.8 Temperature adjustment
The temperature sensor has to be calibrated at regular intervals to ensure the measured value
is not falsified by incorrect temperature measurement.
1. Determine the temperature with a reference measurement.
2. Depending on the result, decide whether you want to align the temperature sensor of the
sensor with the reference temperature.
If you do:
3. Go to the "CAL/Temperature" menu.
The current offset is displayed. Mode is for information purposes only. You cannot select
anything here.
4. Start the adjustment and follow the instructions.
The transmitter shows the temperature currently measured by the temperature sensor
of the sensor.
5. Enter the temperature of your reference measurement and select "Continue".
The new offset is displayed.

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6. Confirm acceptance of the new calibration data and finish the adjustment by clicking "OK".
The transmitter automatically switches to the measuring mode and the new
temperature offset is used.
You can cancel the calibration any time. No new data are then used to adjust the sensor.
2.9 Calibrate
1. Press the soft key for "CAL".
2. Select the type of calibration.
3. Enter the necessary parameters. (The parameters that have to be configured depend on the
type of calibration selected.)
4. Start the calibration.
5. Follow the instructions in the menu.
6. Decide whether to use the calibration data captured, or to abort or repeat the calibration.
After calibration, the transmitter automatically switches back to the measuring mode
and your measuring point is now ready for operation.
• If calibration is aborted using ESC, or if the calibration is faulty, the system continues to use
the original calibration data.
• A calibration error is shown as plain text on the display.
• Any offset set is automatically deleted after accepting the calibration.

Diagnostics, troubleshooting CM42-MAA101EBE00
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3 Diagnostics, troubleshooting
In the DIAG menu you will find information about the device state, in particular detailed error
and maintenance messages.
In addition to this, there are various service functions available1).
3.1 General troubleshooting
3.1.1 Troubleshooting
The transmitter continuously monitors its own functions.
If an error detected by the device occurs, the red alarm LED lights up and the error number with
the related error message appears on the display.
Troubleshooting instructions
A diagnostics message is shown on the display, measured values are implausible or you discover
an error.
1. See the Diagnostics menu (DIAG/Errors / Messages) for details on the diagnostics message.
2. Search for the diagnostic message under "Diagnostics information on the local display"
(ä18) in this manual. Use the message number as the search criterion. Ignore the letters
indicating the Namur error category.
Follow the troubleshooting instructions provided in the last column of the error tables.
3. In the event of implausible measured values, a malfunctioning local display or other errors,
refer to "Process errors without messages" (ä15) or "Device-specific errors" (ä16).
Follow the recommended measures.
1) Depending on the device version
a0010348-de
Fig. 4: Error messages (example)

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4. Contact the Service Department if you cannot rectify the error yourself. Only cite the error
number.
3.1.2 Process errors without messages
Problem Possible cause Tests and/or remedial measures
Display values deviate
from reference
measurement
Incorrect calibration Repeat the calibration.
Where necessary, check and repeat the calibration
with the reference device.
Sensor fouled Clean the sensor.
Temperature measurement Check the temperature measured values of both
devices.
Temperature compensation Check the settings for temperature compensation
and adjustment for both devices.
Measuring chain
zero-point cannot be
adjusted
Contaminated reference system Test with new sensor
Junction clogged Clean or grind junction
Asymmetric sensor voltage too high Clean junction or test with another sensor
No change or subtle
change in display
– Sensor fouled
–Sensorold
– Sensor defective (reference lead)
Clean the sensor.
Reference has low level of KCl Check KCl feed (0.8 bar above medium pressure).
Measuring chain slope:
– Cannot be adjusted
– Too low
–Noslope
Device input defective Check device directly.
–Sensorold
– Hair-line crack in glass
membrane
Replace sensor.
Constant, incorrect
measured value
Sensor not immersing or protection
cap not removed
Check installation position, remove protection cap.
Air pockets in assembly Check assembly and orientation.
Ground connection at or in device Carry out test measurement in isolated vessel, poss.
with buffer solution.
Hair-line crack in glass membrane Replace sensor.
Device has impermissible operating
status (no reaction to keys being
pressed)
Switch device off and then on again.
Incorrect temperature
value
Sensor defective Replace sensor
Measured value
fluctuations
Interference on signal output cable Check cable routing, route cable separately if
necessary.
Interference potential in medium Eliminate source of interference or ground medium
as close as possible to sensor.

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3.1.3 Device-specific errors
No current output signal
Cable disconnected or
short-circuited
Disconnect cable and measure directly at device.
Output defective See "Device-specific errors" section.
Fixed current output
signal
Current simulation active Switch off simulation.
Incorrect current output
signal
Total load in current loop too high Measure the voltage directly at the device and
compare to diagrams of the power supply and signal
voltage (→Technical data, Part 1).
EMC (interference coupling) Check wiring. Determine the reason for the EMC and
eliminate it.
No HART communication
Incorrect CPU module Check nameplate
• HART interface missing
• Device not registered in HART
server
• Load too low (min. 250 
required)
• Line problems
(too long, cross-section too small,
not shielded, shield not
grounded, cores not twisted)
• Several devices configured on
same address
For further information see: www.endress.com/hart
Problem Possible cause Tests and/or remedial measures
Dark display No supply voltage Check if supply voltage applied.
CPU defective Replace CPU, make sure correct version is
used.
Values appear on display
but:
– Display does not
change and / or
– Device cannot be
operated
Module not wired correctly Check modules and wiring.
Impermissible operating system
condition
Switch device off and then on again.
Implausible measured
values
Sensor module defective First perform tests and take measures as
outlined in "Process-specific errors" section
Test the measuring inputs
1. Instead of connecting the sensor,
connect the Memocheck Sim CYP03D
simulator (accessories, ä37).
2. Check whether the value output by the
simulator is also displayed by the
CM42.
Problem Possible cause Tests and/or remedial measures

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3.1.4 Comunication-related errors
Current output, current
value incorrect
Incorrect adjustment Check with current simulation switched on,
connect mA meter directly to current output
.
Load too large
Shunt / short to ground in current
loop
No current output signal CPU defective Check with current simulation switched on,
connect mA meter directly to current output
.
Problem Possible cause Tests and/or remedial measures
No communication
possible
HART is connected to the wrong
current output
Connect HART to current output 1.
The device reboots Wait for the device to reboot. HART is available as
soon as the measuring screen is displayed.
Current output defective Check the output current at output 1 with an
external multimeter. If it is not possible to set a
current in the range between 3.6 and 21.5 mA, you
must replace the module.
No communication
possible or
communication is
unstable
Communication load (resistance)
outside the permitted range
Connect HART as shown in the wiring diagrams.
Preferably use a 250 resistor.
The device has been connected to an
input of a process control system
that is not designed for this purpose
(e.g. four-wire instead of two-wire).
Connect HART as shown in the wiring diagrams. An
external current source must be provided in the
circuit.
USB HART modem Alternatively use an RS232 modem. Some programs
have problems with USB modems. This has nothing
to do with CM42. Use hardware that you know will
work.
The control system cannot
switch on the burst mode
CM42 does not support the burst
mode
Use the device without the burst mode.
The unit of the
transmitted device
variable does not match
the unit on the display
The display and HART are
independent of one another
• Set the unit of the HART device variables with
FieldCare, for instance.
• Not all units are available through HART. In such
situations, the PCS displays "not defined" or , for
example, instead of M.
• Use a DD (device description) for your PCS. You
can download DDs and DTMs (Device Type
Managers) for common PCSs (FieldCare,
Pactware, ABB, AMS, PDM, FC475) from the
Endress website.
Problem Possible cause Tests and/or remedial measures

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3.2 Diagnostic information on local display
The table of diagnostics messages is sorted by the message number. This number cannot be
changed. The "Cat." column contains the error category which is assigned at the factory .
Document all the changes you make for your measuring point in the diagnose list (→
SETUP/Sensor/Sensor diagnostics/Diagnostics list or SETUP/General settings/Device
diagnostics/Diagnostics list).
No communication in a
Multidrop network
Incorrect bus addresses Each device in the Multidrop network must have a
unique bus address, preferably in the range from 1
to 15.
Incorrect connection All the devices must be connected in parallel.
The devices in the network do not
meet the Multidrop requirements
Do not mix devices with active and passive current
outputs. Test whether the network works if you have
only connected CM42x devices.
The loop current does not
match the value on the
display
The loop current has been adjusted
by the user
Reset the loop current with FieldCare, for instance. If
you do not have a HART tool, reset the device to the
factory default settings via the local operation.
→Diagnostics/Systemtest/Factory default
HART tag does not match
the device designation on
the display
PCS uses the short tag instead of the
long tag
Set the short tag to the desired value (only possible
via HART).
Damping cannot be set for
PV
Damping is not supported by all the
device variables
-
Not possible to read or
write a special parameter
or value
Your application Use device drivers (DD/DTM) where possible. If you
are programming your PCS yourself, you can find a
complete list of all the supported HART commands,
with the associated data content, in the document
SD01325C (on the Internet).
No. Display text Cat. Tests and/or remedial measures
003 Temp. sensor failure F – Check wiring
004 Scanning sensor C Establishing a connection to the sensor
010 Sensor initialization C Wait for the initialization to finish.
011 Sensor no communication F – Data processing interrupted due to user interaction with DAT module
(F011)
– Check the measuring chain with a new sensor
– Check the settings for the sensor type used.
012 Sensor failure F
013 Wrong sensor type F
014 Invalid sensor data C
100 Glass impedance alarm F
– Check glass electrode for breakage and hairline cracks
– Check medium temperature
– Check electrode plug-in head for moisture and dry if necessary
Problem Possible cause Tests and/or remedial measures

CM42-MAA101EBE00 Diagnostics, troubleshooting
Endress+Hauser 19
101 Ref. impedance alarm F – Check reference electrode for contamination and damage
– Clean reference electrode
102 Glass imp. too low alarm F – Impedance of glass membrane too low
– Check pH sensor, replace if necessary
103 Ref. imp. too low alarm F
– Reference impedance too low
– Check reference electrode for contamination/clogging
– Replace reference or combined electrode
104 Sensor supply bad F
– Sensor operating voltage fluctuating
– Check connection
– Replace sensor cable or sensor
106 Glass impedance warning M
– Check glass electrode for breakage and hairline cracks
– Check medium temperature
– Check electrode plug-in head for moisture and dry if necessary
107 Ref. impedance warning M – Check reference electrode for contamination and damage
– Clean reference electrode
111 Glass imp. too low warning M
– Check glass electrode for breakage and hairline cracks
– Check medium temperature
– Check electrode plug-in head for moisture and dry if necessary
112 Ref. imp. too low warning M – Check reference electrode for contamination and damage
– Clean reference electrode
119 Temp offset lower limit F – Check the temperature sensor of the sensor
– Clean the sensor and recalibrate
– Replace sensor
120 Temp offset lower limit F
127 Invalid TAG group F Use a sensor with a suitable sensor designation or sensor group.
128 Invalid TAG F
129 Sensor change aborted C Restart the sensor change
130 Calibration active C Wait for the calibration to finish.
131 PV not stable M – Sensor too old
– Cable or connector defective
132 Temperature not stable M
134 Zero pnt. too high alarm M
– Sensor old or defective
– Diaphragm blocked
– Buffer solutions too old or contaminated
135 Zero pnt. too high warning M
136 Zero pnt. too low warning M
137 Zero pnt. too low alarm M
138 Slope too low alarm M
139 Slope too low warning M
No. Display text Cat. Tests and/or remedial measures

Diagnostics, troubleshooting CM42-MAA101EBE00
20 Endress+Hauser
172 Operating time alarm M
The operating time for the sensor which you specified has been reached.
Replace the sensor to ensure the operability of the measuring point. If a
new sensor is used, the counters are reset to the new sensor data.
173 Oper.time >80°C alarm M
The sensor has reached the operating time under extreme conditions
which you specified. Replace the sensor to ensure the operability of the
measuring point. If a new sensor is used, the counters are reset to the
new sensor data.
174 Oper.time >100°C alarm M
175 Oper.time <-300mV alarm M
176 Oper.time >300mV alarm M
177 Delta slope alarm M Sensor aged. Replace the sensor.
178 Delta zero alarm M
180 Cal. expired alarm M The operated hours counter has reached its limit. Perform a calibration.
This resets the counter.
181 No. steril. alarm M The number of sterilizations which you specified has been reached.
Replace the sensor.
182 Operating time warning M The operating time for the sensor which you specified has almost been
reached. Prepare to replace the sensor.
183 Oper.time >80°C warn M
The sensor will soon have reached the operating time under extreme
conditions which you specified. Prepare to replace the sensor.
184 Oper.time >100°C warn M
185 Oper.time <-300mV warn M
186 Oper.time >300mV warn M
190 Cal. expired warning M The operated hours counter is reaching its limit. Plan a calibration.
191 No. steril. warning M The number of sterilizations which you specified will be reached shortly.
203 Wrong transmitter type F Use a sensor module that suits the software.
(Software version 10... for pH, 13... for conductivity, 20... for oxygen)
215 Simulation active C Active corresponding to your settings
218 Current output not available F Contact the Service Team!
219 Power supply bad C
Interference amplitude of power supply too high
– Incorrect power supply or unshielded cables used
– Connect the device to a clean power supply.
– Make sure the cable is grounded correctly.
– The error is not rectified until the interference amplitude is gone or if
it is in the frequency range for HART communication.
238 Delta slope alarm C Sensor aged. Replace the sensor.
239 Delta zero alarm C
318 Glass imp. too high alarm M
Sensor check system warning
– Check glass electrode for breakage and hairline cracks
– Check medium temperature
319 Ref. imp. too high alarm M
Sensor check system warning
– Check reference electrode for contamination and damage
– Clean reference electrode
No. Display text Cat. Tests and/or remedial measures