PNP vs NPN Proximity Sensor
PNP vs NPN proximity sensors in one line: a PNP sensor switches +24 V to its output when it detects a target, and an NPN sensor switches 0 V. Choose PNP for sinking PLC inputs (the usual case in Indian panels) and NPN for sourcing inputs.
This guide covers the wiring colours, NO vs NC and how to choose, plus every PNP and NPN proximity sensor we stock, with live prices. Prices checked 17 October 2026. Reviewed by Amit, Voltkart.
Proximity sensor wiring colours (3-wire DC)
| Wire colour | Connect to | PNP sensor | NPN sensor |
|---|---|---|---|
| Brown | +24 V DC (supply positive) | Supply + | Supply + |
| Blue | 0 V (supply negative) | Supply 0 V | Supply 0 V |
| Black | Output (NO) | Switches +24 V to the load / PLC input | Switches 0 V to the load / PLC input |
| White (4-wire types) | Second output (NC) | Complementary output | Complementary output |
PNP and NPN proximity sensors in stock
| Model | Output | Contact | Size | Price |
|---|---|---|---|---|
| Autonics PR12-4DP2 | PNP | NC | M12 | ₹1,063 |
| Autonics PR18-8DP2 | PNP | NC | M18 | ₹1,311 |
| Omron E2B-S08KS02-WP-B1 | PNP | NO | M8 | ₹670 |
| Omron E2B-M12KS04-WP-B1 | PNP | NO | M12 | ₹670 |
| Autonics PR12-2DP | PNP | NO | M12 | ₹990 |
| Autonics PR12-4DP | PNP | NO | M12 | ₹990 |
| Autonics PSN17-5DP | PNP | NO | 17 mm square | ₹910 |
| Omron E2B-M18KS08-WP-B1 | PNP | NO | M18 | ₹670 |
| Autonics PR18-5DP | PNP | NO | M18 | ₹990 |
| Autonics PR18-8DP | PNP | NO | M18 | ₹990 |
| Autonics PR12-4DN2 | NPN | NC | M12 | ₹1,063 |
| Autonics PR18-8DN2 | NPN | NC | M18 | ₹1,311 |
| Omron E2B-S08KS02-WP-C1 | NPN | NO | M8 | ₹670 |
| Omron E2B-M12KS04-WP-C1 | NPN | NO | M12 | ₹670 |
| Autonics PR12-2DN | NPN | NO | M12 | ₹990 |
| Autonics PR12-4DN | NPN | NO | M12 | ₹990 |
| Autonics PSN17-5DN | NPN | NO | 17 mm square | ₹910 |
| Omron E2B-M18KS08-WP-C1 | NPN | NO | M18 | ₹670 |
| Autonics PR18-5DN | NPN | NO | M18 | ₹990 |
| Autonics PR18-8DN | NPN | NO | M18 | ₹990 |
Inductive sensors detect metal; sensing distance grows with body size (M8 about 2 mm, M12 about 2–4 mm, M18 about 5–8 mm). For photoelectric, fibre and temperature sensors, see the full sensor guide and price list, or browse Omron and Autonics. Need a 24 V supply too? See the sensor + 24 V power kits.
PNP vs NPN: frequently asked questions
What is the difference between a PNP and an NPN sensor?
Both are 3-wire DC sensors. A PNP sensor switches the positive supply (+24 V) to its output when it detects an object; it "sources" current. An NPN sensor connects its output to 0 V when it detects an object; it "sinks" current. The sensing itself is the same; only the output polarity differs.
Which one should I use with my PLC?
Match the sensor to the PLC input type. Sinking inputs (common terminal at 0 V) need PNP sensors, which is the usual case in Europe and most Indian panels. Sourcing inputs (common terminal at +24 V) need NPN sensors, which are common on Japanese and some older machines. Check the PLC manual or the input common wiring before ordering.
What do NO and NC mean on a proximity sensor?
NO (normally open) means the output turns ON when a target is present. NC (normally closed) means the output is ON with no target and turns OFF when a target is present. NC is often used for safety or fail-safe end positions.
What do the wire colours mean?
On standard 3-wire DC sensors, brown is +V, blue is 0 V and black is the output. 4-wire types add white for a second, complementary output. Always confirm with the label on the sensor.
Can I replace a PNP sensor with an NPN one?
Not directly: the output polarity is opposite, so the PLC input or relay will not see the signal correctly. Replace like with like, or change the input wiring or use an interposing relay.
Need help matching a sensor to your PLC or machine? Send the model number or a photo on WhatsApp 8800754881 (Mon–Sat, 12:30–7 pm).