Hi I have 2 water tanks in my motorhome that have resistive level senders, I would like to also use the Cerbo GX to monitor them as well. Can they be paralled or do I need to disconnect the factory gaug?
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Cerbo gx tank level in parallel
You can not connect one resistive sensor to two monitoring devices. Both monitoring devices will draw current and both monitors will show incorrect levels.
As you don't know what the gauge does (Voltages at the sensor), disconnecting may be a good idea.
@Big Ste , The Cebo GX comes with resistive sensor inputs as standard. If you parallel the input to the CerboGX across the existing sensors your original gauge will read incorrectly becasue the CerboGX will influence the reading. You could use the Tank140 module which is designed to read the voltage of the sensor. When the original gauge is operational it provides current throught he sensor and hence a voltage across it. The Tank 140 module can read that and provide a level based on your calibration of the reading versus the voltage.
The problem arises when you switch off the ignition and the voltage is lost. In that case the CerboGX can read the tank level when ignition is on but not when ignition is off. That is not very practical as when ignition is on you can just look at the normal gauges.
To make the sytem work at all times you need to have the sensor pass through a relay so when ignition is on the sensor works as normal. When ignition is off, the original gauge is disconnected and a vpotentiometer supplies current to the sensor. This potentiometer is then adjusted so when ignition is switched on and off the Tank 140 reads the same level as the original gauge.
In that way the tank 140 will always be able to read the sensor even when the ignition is off. A two pole relay is required with one pole disconnecting the original guage and the other pole connecting the potentiometer and power source. All of the connections can be made at the sensor.
