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I found a TTL converter box made custom made many years ago. It says Namur_to_TTL converter on it. What is Namur? I googled but couldn't find a clear explanation.

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NAMUR is a signaling standard, used primarily on proximity and limit switch devices. It outputs a current signal depending on the state of the switch. The switching spec is >2.1mA (typically but not always for NC) and <1.2mA for the opposite switch state. There is a 0.9mA deadband for noise immunity. The output is usually characterized at an output of 8.2V when terminated with a 1k resistor. Because of the nature of the signal, a conditioning circuit is needed to convert back to 0/5V or 0/24V logic levels.

The standard was developed in Germany in the late 1940s for use in chemical plants. "Normenarbeitsgemeinschaft für Mess- und Regeltechnik in der Chemischen Industrie" was shortened to NAMUR. The standard is contained within EN 60947-5-6.

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  • \$\begingroup\$ Is is serial or analog signalling? Do you know why would that be used ? \$\endgroup\$ – GNZ Apr 11 '18 at 17:29
  • \$\begingroup\$ Not aware of serial PCM data transmission using NAMUR, however I have seen shaft encoders that do. Here's one reference: docuthek.kromschroeder.com/documents/… All of my experience with NAMUR has been with proximity sensor applications. Because of the hysteresis, I doubt it was ever intended for analog signaling. \$\endgroup\$ – AlmostDone Apr 11 '18 at 17:34
  • \$\begingroup\$ Very strange I think its not used often. I still dont understand how it works. Not serial not analog so what is that.. \$\endgroup\$ – GNZ Apr 11 '18 at 17:44
  • \$\begingroup\$ @GenzoWakabayashi Proximity sensors are used extensively in industrial automation and process industries. The sensors are used to detect the presence or position of an object. Unlike a mechanical switch, these sensors don't wear with use, are fully sealed, and have built in open and short circuit fault detection capability through the NAMUR interface module. Here is one manufacturer's sensor product offering: pdb2.turck.de/us/DE/groups/000000010002461b00030023 in case you want further look at this type of sensor. \$\endgroup\$ – AlmostDone Apr 11 '18 at 21:25
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    \$\begingroup\$ @GenzoWakabayashi it's digital, but it's what's called "current-mode" instead of the more traditional "voltage-mode". Current-mode signaling can provide better noise immunity and in some cases higher speed than voltage-mode signaling. Current-mode signaling usually requires more power than voltage-mode signaling because P = I * V and voltage-mode signaling usually involves very small currents. \$\endgroup\$ – alex.forencich Apr 12 '18 at 3:26
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NAMUR signalling is based on a current-loop style interface instead of digital (on/off), voltage style. It is mainly used in explosive atmospheres and is part of an "Intrinsically Safe" connection strategy. The current and voltage are, by design, low enough to prevent a spark of sufficient energy to ignite an explosive atmosphere. It must therefore be used with an "Intrinsic Barrier" style amplifier before it can be used to signal a PLC or Process controller.

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