When wiring industrial automation sensors, the Turck 4 wire cable color code with pinout diagram strictly follows the IEC 61076-2-101 standard for M8 and M12 circular connectors. For a standard 4-pin DC sensor pigtail, Pin 1 is Brown (+VDC), Pin 2 is White (Signal A), Pin 3 is Blue (0V/GND), and Pin 4 is Black (Signal B). While the sensor-side pigtail is globally standardized, landing those wires into a regional control panel requires careful translation to avoid short circuits and code violations.
Turck 4-Wire M12 Pinout and Color Code Reference
The table below maps the physical M12 connector pins to the standard Turck 4-wire color code. This applies to the vast majority of Turck proximity, photoelectric, and capacitive sensors operating on 10-30V DC.
| Pin | Wire Color | Abbreviation | Primary Function (Standard DC) | IEC 61076-2-101 Mapping |
|---|---|---|---|---|
| 1 | Brown | BN | +VDC (Typically 24V DC) | Power Supply (Positive) |
| 2 | White | WH | Output A / Signal 1 (NO or NC) | Control Signal 1 |
| 3 | Blue | BU | 0V / GND | Power Supply (Negative/Return) |
| 4 | Black | BK | Output B / Signal 2 (NO or NC) | Control Signal 2 |
Rows People Get Wrong (and How to Fix Them)
Even experienced panel builders make assumptions about sensor pigtails that lead to frustrating debugging sessions on the bench. Here are the most common misinterpretations of the table above:
- Assuming White is Always NO and Black is Always NC: On dual-output Turck sensors (like the BI10U-M30 series), White is Output 1 and Black is Output 2. However, whether Output 1 is Normally Open (NO) or Normally Closed (NC) depends entirely on the specific sensor's logic configuration, not the wire color. Always verify the NO/NC logic in the specific sensor datasheet before wiring the PLC input card.
- Tying the Shield to Blue (0V): In environments with heavy VFD noise, tying the M12 cable shield drain to the 0V reference (Pin 3) creates a ground loop. This induces phantom voltages on the White and Black signal wires, causing the PLC to register false triggers. The shield must be bonded to the panel's equipotential bonding grid or the M12 connector's metal coupling nut.
- Misidentifying Pin 1 on the Male Face: When looking at the male M12 connector face (the side with the pins, not the sockets), Pin 1 is not at the top. With the plastic keyway aligned at the bottom (6 o'clock), Pin 1 is at the top left (10 o'clock), Pin 2 is top right (2 o'clock), Pin 3 is bottom left (8 o'clock), and Pin 4 is bottom right (4 o'clock).
Regional Clashes: IEC Sensor Cables vs. NEC and Old UK Panels
The Turck pigtail follows IEC standards, but the control panel you are wiring it into might follow entirely different regional codes. Mixing IEC sensor colors directly into a US NFPA 79 panel or an older UK machine without transitioning the wire colors is a major code violation and a safety hazard for future maintenance technicians.
| Wire Function | IEC 61076 (Turck M12 Pigtail) | NFPA 79 (US Control Panel Standard) | Old UK (Pre-2006 Machinery) |
|---|---|---|---|
| DC Positive (+24V) | Brown (BN) | Blue (BU) or Red (RD) | Red (RD) |
| DC Negative (0V) | Blue (BU) | Blue w/ White Stripe or Black (BK) | Black (BK) |
| Signal / Output | White (WH) / Black (BK) | Orange (OG) or Yellow (YE) | Yellow (YE) |
| Protective Earth | Green/Yellow (GN/YE) or Bare | Green/Yellow (GN/YE) | Green (GN) |
As detailed in the NFPA 79 Electrical Standard for Industrial Machinery, DC control circuits in the US require specific color coding to differentiate them from AC power and grounding conductors. Directly landing a brown IEC wire onto a US +24VDC busbar confuses the color logic of the entire cabinet.
Decision Tree: Landing Your Turck Pigtail in the Control Panel
Use this decision path to determine exactly how to terminate your Turck 4-wire cable based on your panel's regional standard and sensor type. This terminates in a concrete hardware pick.
| Condition | Action / Routing | Concrete Hardware Pick |
|---|---|---|
| If wiring an IEC panel (EU/Global) with a standard PNP sensor... | Land Brown to +24V, Blue to 0V, and White/Black directly to the PLC input terminals. | Phoenix Contact UTTB 2.5 multi-level terminal blocks. |
| If wiring a US NFPA 79 panel with a PNP sensor... | Land the IEC Brown/Blue to a dedicated DC power terminal block. Use an Orange (OG) jumper wire from the terminal block to the PLC input to maintain US signal color code. | Weidmüller WDK 2.5 terminal blocks with integrated test points for the signal transition. |
| If the sensor is NPN (sinking) in a US panel... | Land Blue (0V) to the PLC input common. Use Orange (OG) for the signal wire, ensuring the PLC input card is configured for sinking logic. | Phoenix Contact UTTB 2.5-PE for the shield, standard UTTB 2.5 for signals. |
| If the cable has a bare shield drain wire... | Terminate the shield to the panel ground bus. Do not route it through the signal terminal blocks. | Phoenix Contact UTTB 2.5-PE (Protective Earth terminal block with direct DIN rail contact). |
For 90% of North American retrofits involving Turck M12 pigtails, the default best practice is to use a Phoenix Contact UTTB 2.5 series terminal block as a transition point. This allows you to land the IEC-colored pigtail on the bottom tier, and jump to NFPA-compliant Orange/Blue wiring on the top tier, keeping both standards visually distinct and physically separated.
Safe Interpretation When Markings are Faded or Missing
In harsh environments, machine cutting fluids (like Trim Sol or Castrol Alusol) and UV exposure will completely erase the printed pinout legends on a Turck cable jacket within six months. If you inherit a machine with unmarked, faded, or custom-spliced 4-wire cables, do not guess the pinout based on the jacket color alone—manufacturers occasionally use non-standard jacket colors for specific OEM runs.
Follow this bench procedure to safely map the wires:
- De-energize the Circuit: Lock out and tag out the 24VDC power supply feeding the sensor. Verify 0V at the terminal block with a multimeter.
- Disconnect the M12 Connector: Unplug the sensor pigtail from the PLC or junction block.
- Set Multimeter to Continuity: Use a reliable meter (e.g., Fluke 87V or 117) in continuity/diode test mode.
- Probe the Male Connector Face: Place one probe on the bare wire end and the other on the M12 male pins. Remember the clock-face rule: Keyway at 6 o'clock, Pin 1 at 10 o'clock, Pin 2 at 2 o'clock, Pin 3 at 8 o'clock, Pin 4 at 4 o'clock.
- Map and Label: As you identify each wire, immediately wrap it with a Brady or Panduit self-laminating wire marker indicating both the IEC color code and the target terminal number.
For deeper technical specifications on M12 connectivity and sensor integration, refer to the Turck Connectivity Product Guide or consult the IEC International Standards catalog for the full IEC 61076-2-101 documentation. Always prioritize the specific datasheet of the sensor module you are installing, as specialized IO-Link variants may repurpose Pin 2 and Pin 4 for digital communication rather than discrete switching.
