NAMUR Proximity Sensor Current Calculator
Work out the current a NAMUR (IEC 60947-5-6) proximity sensor or resistor networked contact draws from an 8.2 V, 1 kΩ isolating amplifier, and the state the amplifier reports.
- I = 1.6 mA (measured)
- Switching: OFF ≤ 1.2 mA, ON ≥ 2.1 mA (IEC 60947-5-6)
- Line break ≤ 0.2 mA, short circuit ≥ 7 mA (amplifier settings)
NAMUR Sensor Values (IEC 60947-5-6)
OFF ≤ 1.2 mA, ON ≥ 2.1 mA
Line break and short circuit thresholds: set by the amplifier
A NAMUR sensor changes its internal resistance between two states. The isolating amplifier supplies about 8.2 V through about 1 kΩ and decides the state from the current. Line break and short circuit limits vary by amplifier; typical values are around 0.1 to 0.2 mA and 6 to 7 mA, so enter those from your module datasheet. Mechanical contacts need a resistor network (often 400 Ω to 2 kΩ series and 10 kΩ parallel) for line monitoring.
Worked example
A sensor reading 1.6 mA sits in the switching band, so the amplifier keeps its last state. A contact with 1 kΩ in series draws 8.2 ÷ 2000 = 4.1 mA and reads ON.
Frequently Asked Questions
What is a NAMUR sensor?
A two wire sensor to IEC 60947-5-6 (originally DIN 19234) whose current changes between below 1.2 mA and above 2.1 mA, read by an isolating switch amplifier.
Why add resistors to a dry contact?
A bare contact gives only open or short. A series and a parallel resistor make open and closed contacts draw normal currents, so a cut or shorted cable is detected.
Can I connect a NAMUR sensor to a 24 V PLC input?
Not directly. Use a NAMUR isolating amplifier or a PLC input module rated for NAMUR sensors.
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