question

bricki avatar image
bricki asked

Pinout of resistive tank inputs of a Cerbo GX

Does anyone know, if some of the Pins of the four resistive tank inputs are connected to GND or 5V?

I‘m asking if I have to wire all eight pins for four sensors or if it‘s enought to wire one GND and four signal pins from the sensors...

Thanks

Peter

cerbo gxtank monitor
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brent626 avatar image brent626 commented ·

The Cerbo provides the voltage via one pin per tank. The voltage drop across the tank level sensor is felt on the other pin. I am not at my boat to test it, but you should be able to measure the power on the pins to see which is the supply and which is the return.


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Kevin Windrem avatar image
Kevin Windrem answered ·

The positive pin for each sender is pulled up to +5 volts with a 680 ohm resistor. Resistive senders are 0-180 ohm (European) or 240-30 ohm (US) and result in roughly 0 to 1.3 volts and up to about 7.5 mA per sender.

All the negative pins are common to. If practical, return all senders to the respective negative pin. If that isn't possible, a common connection should also work. 40 feet of 20 AWG wire would result in a 1% error in tank level. That is 3 tanks with minimum resistance would result in a 1% error in the OTHER tank.

I would not connect sender negatives to chassis as the voltage drop back to Cerbo could be enough to throw off the reading.

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