There isn’t a single universal color code for sensor wiring. The most common scheme in modern industrial sensors is brown for the positive supply, blue for the return/ground, and black for the signal output in three‑wire configurations. Two‑wire sensors typically use brown and blue with no separate output lead, while four‑wire sensors add an extra wire (often white) for a second output or status line.
Common color conventions for DC sensors
The following outlines the color mappings you’ll typically see in DC-powered sensors used in automation. Individual devices may differ, so always check the datasheet.
- Three‑wire DC sensors: Brown = +V, Blue = 0V, Black = output signal (the type of output—NPN or PNP—depends on the sensor).
- Two‑wire DC sensors: Brown = +V, Blue = 0V; there is no dedicated output lead—the sensor acts as a switch in series with the load.
- Four‑wire DC sensors: Brown = +V, Blue = 0V, Black = output 1, White = output 2 or other secondary function such as a second channel or teach input.
Because manufacturers may use variations (for example gray or green for second outputs), always confirm the specific color scheme in the device manual before wiring.
AC-powered and mixed-signal sensors
Not all sensors run on DC; for AC-powered devices and sensors with multiple signal outputs, color coding can vary more widely. When in doubt, consult the product datasheet or labeling on the device.
- Two‑wire AC sensors: often Brown = Live, Blue = Neutral; there is no separate output lead in the traditional sense.
- Sensors with multiple outputs (analog or digital) often employ extra leads in colors chosen by the manufacturer (for example black or white for signal leads); there is no universal scheme beyond the power leads.
Always rely on the device labeling and datasheet to confirm which lead carries which function.
Regional standards and practical guidance
Different regions and industries have leaned on different conventions, though many automation vendors align with a common European practice for convenience.
- Europe and many automation suppliers: Brown = +V, Blue = 0V, Black = output (three‑wire). Additional colors (e.g., White) for extra channels or functions.
- North America: Aimed to follow similar color codes for compatibility, but variations exist across brands and applications. Always verify with the manual.
In all cases, the best practice is to rely on the device documentation and labeling rather than assuming a color mapping.
Summary
Sensor wiring colors are not globally standardized beyond general trends. The most widely used scheme in DC automation is Brown for +V, Blue for 0V, Black for signal output in three‑wire configurations; two‑wire sensors use Brown/Blue with no separate output lead, and four‑wire sensors add a White lead for a second function. Always check the specific sensor’s datasheet or labeling to confirm the exact color assignments for your setup.