The Leuze CRT448 Color Sensor is a high-performance optoelectronic device designed for accurate, contactless detection of colored objects. With its robust feature set and precise operation, it is widely used in industrial automation applications, including quality control, sorting, and object detection across various materials.
Simultaneous detection of up to 3 colors
Distance-independent color detection
Teach-in functionality via button or control line
Temperature compensation
IP67-rated protection
Special functions such as color gradient scan, pulse stretching, and external teach-in
Unlike conventional sensors that distinguish between light and dark or matte and shiny surfaces, the CRT448 identifies specific colors. It compares a taught color against detected values and activates the relevant output if the match lies within a configured tolerance range.
The sensor allows multiple color configurations using the teach-in method:
Start setting mode: Place object in range, press SET ≥ 3s.
Select channel: Choose between Ch. 1, 2, or 3.
Confirm selection: Press SET ≥ 3s.
Select tolerance level (1 to 5):
Tolerance 1: Strict
Tolerance 5: Lenient
Exit setting mode: Press SET ≥ 3s.
Tip: Use the green LED as a guide – if it’s OFF, increase the tolerance level.
Ideal for scanning variable color patterns:
Press and hold SET for 10s.
While SET is held, move the object to scan gradient.
Release SET to complete the scan.
Activated by selecting all three channels (Ch. 1+2+3) and confirmed via the SET button:
Pulse stretching: Extends switching signals to 50ms
External teach-in (PNP types only): Allows remote teach-in of a new color
Factory reset: Restores default configuration
Green LED: Power ON / teach-in active
Yellow LEDs (Ch. 1–3): Indicate detection of corresponding taught color
Red LEDs (Tol. 1–5): Indicate tolerance level during teach-in
| Feature | S Light Spot | L Light Spot |
|---|---|---|
| Scanning Range | 12–32 mm | 18–22 mm |
| Light Spot Size | Ø 4 mm | 1 mm × 5 mm |
| Orientation | Vertical | |
| Light Source | White LED (100,000 h life) | |
| Operating Range (Reflector Mode) | 50–200 mm with TKS 100×100 |
Switching Frequency: 500 Hz
Response Time: 1 ms
Start-up Delay: ≤ 500 ms
Teach Storage Time: ≤ 50 ms (non-volatile)
Voltage Range: 12–28 VDC
Ripple Tolerance: ≤ 10% of UB
Output Options: 3× PNP or NPN
Max Output Current: 100 mA/output
No-load Current: ≤ 40 mA
Signal Levels:
PNP: ≥ UB–3V / 0V
NPN: UB / ≤ 3V
Housing: ABS Plastic
Optics Cover: PMMA
Weight: 40 g
Connector: M12, 8-pin
Operating Temp: -10°C to +55°C
Storage Temp: -20°C to +70°C
Protection: IP67
Eye Safety: EN 62471 Exempt Group
Safety Class: II, all-insulated
Protective Circuits: Polarity reversal, short-circuit protection
Standards: IEC 60947-5-2
Certifications: UL 508 (only for Class 2 circuits under NEC)
Synchronization input (PNP/NPN) with <2ms delay
Key lock input for secure teach-in
External teach-in via Q3 (PNP only)
For shiny objects, mount the sensor at a 10–30° angle to avoid reflection errors.
A reflector is needed for transmitted light mode.
| Model | Scanning Range | Light Spot | Output | Connector |
|---|---|---|---|---|
| CRT448.S3/444-M12 | 12–32 mm | Round | 3x PNP | M12 |
| CRT448.L3/444-M12 | 18–22 mm | Linear | 3x PNP | M12 |
| CRT448.S3/222-M12 | 12–32 mm | Round | 3x NPN | M12 |
| CRT448.L3/222-M12 | 18–22 mm | Linear | 3x NPN | M12 |
M12, 8-pin cable
Reflectors (e.g., TKS 100×100)
The CRT448 sensor is suited for:
Sorting by color
Detecting color labels
Inspection of painted surfaces
Monitoring color consistency in packaging, textiles, and plastics
Detection of liquids, granulates, or powders
Sensor does not power ON
→ Check if the power supply is within 12–28V DC range.
Green LED does not illuminate
→ Ensure polarity is correct and connector is firmly attached.
Frequent power drops
→ Verify that residual ripple is ≤10% of UB.
No response from sensor
→ Confirm the correct wiring to the 8-pin M12 connector.
Open-circuit current exceeds limits
→ Ensure sensor load does not exceed 100 mA per output.
Teach-in process does not start
→ Check if the locking input is open or at 0V. Press SET ≥ 3s.
Wrong channel selected during teach-in
→ Make sure not all three yellow LEDs (Ch.1+2+3) are ON at once.
Cannot change tolerance level
→ Use the arrow button to scroll through Tol. 1–5 before finalizing.
Sensor not storing taught color
→ Confirm that the teach-in is completed with a ≥3s SET press.
Incorrect tolerance feedback
→ If green LED is OFF after teach-in, increase tolerance level.
Unable to perform factory reset
→ Select Ch.1+2+3 > Confirm > Select “Factory Settings” (Tol. LED 3).
Teach-in takes too long
→ Make sure the object is stable and well positioned in the scan range.
Sensor not recognizing color gradient
→ Press and hold SET for 10s until blinking begins, then move object.
Gradient teach-in doesn’t save
→ Release SET only after scanning full gradient on object.
Sensor not detecting shiny objects
→ Mount sensor at a 10–30° angle to avoid reflections.
Inconsistent detection across distances
→ Teach-in color at different distances and select optimal tolerance.
Sensor missing object in fast motion
→ Use Pulse Stretching (50ms) to extend signal output time.
Multiple LEDs light up at once
→ Reduce tolerance level or check for overlapping color thresholds.
False detection or signal noise
→ Ensure clean sensor window and stable lighting conditions.
Object detected outside the range
→ Confirm object is within 12–32 mm (S type) or 18–22 mm (L type).
Synchronization delay too high
→ Delay should be <2ms. Check wiring for sync signal integrity.
External teach-in not working (Q3 input)
→ Available only in PNP versions. Check signal HIGH (>12V) for teach-in.
Sensor reacts late to sync signal
→ Verify timing and proper grounding of sync/control line.
No output after sync trigger
→ Ensure sync input is connected and not floating.
No output signal when object is detected
→ Check output mode (PNP/NPN) matches system input requirements.
Weak signal to controller/PLC
→ Signal high should be ≥ (UB - 3V) for PNP, or ≤3V for NPN.
One channel not responding
→ Re-teach the channel individually and test its output.
All channels fail simultaneously
→ Check for short circuit or overcurrent. Sensor includes short-circuit protection.
Output stuck in HIGH state
→ Ensure color is not always in tolerance zone or reduce tolerance level.
Frequent misclassification between similar colors
→ Reduce tolerance level or use L-profile sensor with finer resolution.
The Leuze CRT448 color sensor is a robust and versatile solution for precise color-based detection in industrial environments. With reliable performance, user-friendly setup, and advanced teach-in capabilities, it is a vital tool for automation where color is a key identifying attribute.