Vela Navega Forum

The old Silva Instruments are having only a current loop output.
https://www.gotthardt-yacht.de/media/pd ... glisch.pdf
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I would like to connect it to the Mux.
My sought: Connect a 470 ohm resistor between +12volt and Input A on the Mux and Data out of the Silva to Input B on the Mux.
Will this work?

Hello,

I am not familiar with 4-20mA current loops but I would do as follows:

- connect plus terminal of battery to 12V of multiplexer and the + terminal of your sensor.

- connect the - terminal of the sensor to A1.

- connect B1 to GND.

- use 220 ohms resistor between A1 and B1.

When current is 4 mA the voltage across A1 and B1 will be 880mV which is not enough to trigger the input optocoupler of the multiplexer. A LOW will be read. When the current is 20mA the voltage will be 4.4V which will trigger the multiplexer. An HIGH will be read.

You can interchange A1 with B1 (I am not sure if 4mA is a LOW or an HIGH). No harm to the multiplexer.

Good luck, Luis in Agios Nikolai, Greece.