The CLM223 is a panel-mounted conductivity transmitter from the Endress+Hauser Liquisys M series, typically paired with CLS series conductive or inductive sensors. Many field engineers are initially baffled by this "little blue-screened box" and its nested menu structure (Setup 1 / Setup 2 / Output). This article outlines the commissioning process in a logical sequence—from wiring checks and menu access to conductivity parameters, temperature compensation, current output configuration, and final calibration/start-up—to help you get it running smoothly on the first try.
Pre-commissioning essentials: Have the sensor's factory calibration certificate (which lists the cell constant) and a small flat-head screwdriver ready. Before changing any parameters, record the existing settings; while the "S9 = Facty" option in the Service menu allows for a factory reset if things go wrong, doing so will erase all your custom configurations.
I. Wiring Check (The Physical Foundation of Commissioning)
The terminal block layout for the CLM223 is clearly defined in the official manual; be sure to verify connections against the diagram before commissioning:
- Power supply: Connect 220 V AC to L1/N; connect 24 V DC to the +/− terminals.
- Conductive sensors: Connect the three temperature wires (green/white/yellow) to terminals 11/12/13; connect the main measurement signal wire to terminal 83 and the auxiliary wire to terminal 84.
- Inductive sensors: Connect the red-blue wire to 83, red-red to 16, white-blue to 84, and white-red to 15.
- Shielding: The outer shield of the conductive sensor cable must be connected to the PE terminal (this is crucial for measurement stability; failure to ground the shield can cause reading drift).
- Current output: Connect the first channel (conductivity) to 31/32; connect the second channel (temperature, optional) to 33/34. The current output is active.
- NC terminals: Leave unconnected.
The instrument is a Class II device and generally does not require a protective earth connection; however, the conductive sensor's cable shield *must* be connected to the PE terminal to prevent measurement interference.
II. Entering the Setup Menu
The CLM223 operating unit features only three keys: E (ENTER/Confirm), + (Plus/Scroll Down), and − (Minus/Scroll Up). Press + and − simultaneously to exit the current menu.
- Press the E key while on the measurement screen.
- Enter the password "22" and press E to confirm (this password is required for both CAL/calibration and parameter modification).
- Use the + / − keys to navigate to the SETUP 1 function group, then press E to enter edit mode.
III. Setup 1: Conductivity Measurement Configuration
This is the core parameter group; it determines "what is measured" and "how it is displayed."
Key Operational Points:
- A5 Electrode constant: Must match the sensor calibration certificate exactly; this is fundamental to measurement accuracy.
- A6 Cable resistance compensation: Applies only to conductive sensors; ignore this setting for inductive sensors.
- A1 Operating mode: Switching this mode automatically resets all user parameters—therefore, select the mode first before configuring other parameters.
IV. Setup 2: Temperature Compensation Settings (Important)
Press the − key to navigate to SETUP 2, press E to enter, select B1 Pt100, and press E to confirm; this enables automatic temperature compensation.
B2 Compensation Method Selection Guide:
- lin (Linear compensation): Suitable for the vast majority of standard aqueous solutions; applies linear correction based on a percentage (α) per Kelvin.
- NaCl: Non-linear curve compensation for sodium chloride solutions; complies with IEC 60746 standards; used for saline systems (the α value in B3 is ignored in this mode).
- Pure: Compensation for ultrapure water (neutral contamination).
- PureH: Compensation for ultrapure water (acidic contamination, e.g., cation exchanger outlet); also suitable for ammonia systems.
- Tab: Table-based compensation (supported by the Plus version; allows input of α-T value pairs).
- none: No compensation.
Key Concept: The α value in B3 (default 2.10 %/K) and the reference temperature in B7 (default 25 °C) are distinct concepts. α represents the "percentage change in conductivity per 1°C rise," while the reference temperature is the "baseline temperature to which compensation is applied." Changing B7 does not affect α, and vice versa. Temperature Sensor Calibration Procedure:
If the real-time temperature displayed in B5 differs from the reading on an independent field thermometer, enter the actual measured value from the external thermometer into B5 and press E; the instrument will automatically calculate the offset and store it in B6. This step is crucial for long-term accuracy.
V. Output: Current Output Configuration
After configuring temperature compensation, press the − key to enter the OUTPUT function group:
- 01 Sel.Out: Select output channel — Out1 (conductivity) / Out2 (temperature, optional)
- 03 Sel.Type: Select output characteristic; usually select "lin" (linear)
- 0311 Sel.Range: Select current range; usually select 4–20 mA
- 0312 0/4 mA: Set the measured value corresponding to the lower current limit (e.g., 0 μS/cm)
- 0313 20 mA: Set the measured value corresponding to the upper current limit (e.g., 2000 μS/cm or the upper limit of the process range)
After configuring one channel, if the instrument supports dual-channel output, switch from OUT1 to OUT2 and repeat the steps above to output the temperature as a 4–20 mA signal as well.
Tip for range setting: The values for 0312/0313 do not necessarily have to correspond to "0 to full scale"; they can be scaled to the 4–20 mA range based on the actual process interval, resulting in higher display resolution at the DCS end.
VI. Calibration and Commissioning
Conductivity sensors typically do not require field calibration (the cell constant is calibrated at the factory; simply enter the value from the certificate into A5); however, inductive sensors must undergo an "Air Set" calibration in air:
- Remove the sensor from the medium, clean it, and wipe it dry.
- Press the CAL key and enter the password "22".
- Enter the C1 menu and select the first item (Air Calibration).
- Enter C111 to observe the measured value in air, then press E to confirm and start calibration.
- C112: View the air calibration value.
- C114: Choose to save the calibration data or recalibrate.
Once calibration is complete, press the + and − keys simultaneously to return to the measurement interface.
VII. Alarms and Relays (Optional)
The CLM223 supports alarm contact functions. Within the "Alarm" function group, you can configure alarm limits, hysteresis, and relay switching logic. Specific configuration depends on on-site interlocking requirements; generally, default settings are sufficient. If a fault occurs, a red alarm indicator lights up on the panel; refer to Chapter 8, "System Error Messages," in the manual to troubleshoot.
VIII. Restoring Factory Settings
If parameters have been incorrectly altered or the instrument needs to be repurposed:
- Press E on the main screen and enter password 22 to access the menu.
- Navigate to the Service function group.
- Locate S9 and select Facty.
- Press E to confirm; the instrument will restart and restore factory parameters.
Before restoring factory settings, be sure to record critical parameters such as A5 (cell constant) and O312/O313 (measurement range). Otherwise, you will have to re-enter them from memory after the reset, and measurement accuracy cannot be guaranteed.
IX. Common Commissioning Issues and Solutions
- Issue 1: Measured values are consistently high
→ Usually caused by inorganic scaling/fouling on the electrode. Soak the electrode in a 1:10 diluted hydrochloric acid solution for 30 minutes, then rinse with deionized water; also, verify that the cell constant (A5) matches the value on the calibration certificate.
- Issue 2: Displayed values fluctuate irregularly between 10 and 50 μS/cm
→ Typical power-frequency interference. Check that the cable shield is securely crimped at the terminal block; install a ferrite bead filter (100 MHz) if necessary.
- Issue 3: Significant discrepancy between displayed temperature and actual temperature
→ Go to B5 in Setup 2, compare the reading with an external precision thermometer, and perform an offset adjustment using B6.
- Issue 4: 4–20 mA output does not match the displayed value
→ Check if the range limits set in O312/O313 match the range configured in the DCS; confirm that O1 is set to Out1 rather than Out2.
- Issue 5: After changing B2, the α value for B3 cannot be modified.
→ This is by design: B3 is only active when B2 is set to "lin" (linear). When NaCl, Pure, PureH, or Tab is selected, internal compensation curves take over, and the α setting no longer applies.
The CLM223 menu structure may appear complex, but it essentially follows a three-step process: "Setup 1" defines the measurement, "Setup 2" defines the temperature settings, and "Output" defines the measurement range. As long as the cell constant, temperature compensation method, and range mapping are configured correctly, the rest is just fine-tuning. Taking a photo of the original values before changing parameters is the most cost-effective "insurance" for a field engineer.
If you are using the device with a CLS21 conductivity sensor, the default combination—"cond" mode + Pt100 + "lin" + α=2.10%/K + reference temperature 25°C—meets the requirements for the vast majority of industrial water quality monitoring applications. You only need to switch to the specific NaCl, Pure, or PureH compensation curves when dealing with special media (such as high-concentration NaCl, ultrapure water, or mixed solutions of acids, bases, and salts).
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