Tank Capacity & Temperature Sensors

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Wireless Bluetooth Temperature Sensors for Cerbo in Products List

Knowing the capacity of your tanks is easy with Victron or Simarine and Safiery's tank sensors:

  • Differential pressure sensors use a USA MEM's silicon chip to accurately measure the water level in a tank and therefore the volume in litres. Even in off shaped tanks, the system will integrate the values in a short range as the tank changes shape.
  • Fit to the bottom side of a tank -G1/4 thread
  • Fit on a T-piece before the drain tap
  • Fit into a drain bung directly (most are 3/4 BSP and an adaptor is easily sourced)
  • Undertank Ultrasonic sensors are a quick installation and retrofit when:
  • There is no tank shield
  • There is no paint on the tank
  • The tank material can be glues to (polypropolyene, metal, fibreglass, composites are all good. 

Victron GX Tank 140 

The new Victron GX Tank 140 is usable with all the Safiery voltage based sensors.

Victron GX Tank 140 installed in Dodge ram with compact tank level transmitter

Here are some installed pics:


  • EASY installation.
  • These Ultrasonic sensors fit under the tank, preferably toward the centre of the tank.
  • They glue with a standard 2 part epoxy
  • The alloy surround has a deep channel to capture the excess glue so it doesnt flow to the outside of the sensor.
  • There is a test LED on the sensor that shows:
    • 12V power is available
    • Ultrasonic is working correctly
  • Have the same features as fresh water measurement described above.
  • Can only be installed directly to a tank. There cant be any protective shield around the tank.
  • Fibreglass, metal, polypropolyene tanks are easy to adhere to. Poly-ethylene (the plastic that nothing sticks to) requires some minor surface heating as preparation for fixing sensor.
  • Common today to have ultrasonic sensors reading grey water tank levels asthe sensor cant be fouled.
  • Use the same water filling meter to measure the available volume.


LPG Tank Level Sensor and Pre-processor

Bottle Size: 4kg to 60kg bottle. Includes "swap-n-go" gas bottles.

This sensor attaches magnetically to the bottom of a steel LPG tank

The surface needs to be clean and clear of folded paint or debris. 

The sensor has a digital output which goes to the Pre-processor.

The resultant output is 0-5V suitable for Victron GX Tank 140 or Simarine Monitoring Systems.

Calibration may be needed with a conversion to kg that matches LPG tank capacity when tank is full and fitted.

This sensor requires a 12V power supply.



Problems faced by users with fresh water tanks are:

  • Knowing the usable capacity
  • Know the capacity available in litres

There can be significant differences between the theoretical capacity of a water tank and the usable capacity.

To understand the problems that cause this go to oue ebook which steps through the causes and how to increase usable capacity on virtually any tank.

Determining the usable capacity is easy.

  • Purchase a low cost water filling meter. (one at the end of this article)
  • Drain the water tank on level ground.
  • Fill the tank and measure with the meter until the breather is overflowing just a little.
  • Take the meter reading and subtract a litre of so for the breather tube volume and overflow.

Now you have the maximum usable capacity of your tank.


This is the hard one for most systems. The reason is:

  • Level measurements are used that can be linear in a non-linear tank volume.
  • Level sensors fail or give faulty readings
  • There was no original calibration by the manufacturer and the tank reading are an estimate.

SIMARINE solves these problems in a simple and clever way using Artifical Intelligence.

  • No problem with the water volume remaining estimate in an unusually designed water tank.

For each change of water level sender point (if fixed measuring level points), you enter the volume of water change in litres against a calibration value.

Use one of the simple filler meters and enter the litres for each sender point.

  • Watch the reading level jump when a sensore point is touched by the water
  • Pick a similar interval change for the calibration if a variable analog sensor is used.
  • Dont be concerned about having exact interval points on variable level senders. The system will do the smarts for you.

Victron GX Tank 140


Between "full" and "empty" :

  • 11 calibration points that can be added.
  • View the list of calibration points for a tank and add new calibration points or remove existing ones.
  • More calibration points will enable PICO to show tank level more accurately. 
  • For each calibration point, tank fill volume and a corresponding sensor value (resistance or voltage) must be set.

SIMARINE then calculates the estimated volume change between each sender point and uses a unique change variable. 

Tank Sensors:



VICTRON and SIMARINE work very well with the same 10 calibration points between full and empty with these sensors.


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GX Tank

GX Tank