Security warning

Tank monitor systems should only be installed by a person competent and with experience in working with electrical systems and fuel tanks. All work involving fuel tanks should be performed with extreme care due to the possibility of igniting fuel fumes. Our tank monitor systems are designed to be accurate and reliable. However, they should be used only as aids.

When you install the sensor, you need to be connected to the Internet, but you can be off the Internet when this is done. If you like to watch your tank level on your smartphone, you reach the sensor via Bluetooth. Finally, if you only connect the sensor to a control unit or a gauge, you don’t need your phone or Internet.

This information is in three parts

  • In the box
  • Mounting the sensor on the tank
  • Setup the sensor

In the box

Gobius C is ready to use; everything is in the box. You have the sensor with a 3M tape, a Quick Guide, 3M tissue, a cable to connect to a power source (12-24 V), and also to use for external devices, like warning lights/buzzers, control systems, and analog gauges. The Quick Guide gives you a brief overview of installing the sensor. And the sensor is waterproof IP44.

Mounting the sensor on the tank

Explain how you attach the sensor to the tank and the difference between plastic and metal tanks. For metal tanks, you need a hole in the tank wall. Gobius C cant read through metals like stainless steel, steel, and aluminum. For all kinds of tanks, you need at least 65 mm of space above the tank.

Setup the sensor

Here you can enter exact information for your tank, including size, volume, and type of fluids. In addition, you can choose at which levels you want to receive level alarms and which protocol to set to communicate with external devices properly. You can also edit, save, delete, and do a factory reset. The necessary calibration is also done here.

Let’s start!

Sensor for NMEA 2000

Sensor with analog outputs

Guide 1

Installation on plastic tanks

Please note that this Gobius is mounted on the top of the tank, not on a vertical side. Remember that this top wall must be horizontal, i.e., not inclined.
Maximum tank wall thickness is for polyethylene 12 mm, fiberglass 8 mm, and glass 5 mm.

  1. Find a place not too close to an edge; the minimum distance is 35 mm from the sensor’s edge to the tank’s edge.
  2. Clean the surface of the tank with the 3M tissue. You can also use Acetone.
  3. Check that the temperature on the tank is at least 20C / 76 F.
  4. Place the sensor on the tank and press it hard.
  5. Wait 15 minutes for the tape to harden.

You need at least 65 mm of free space above the tank for mounting the sensor.
This is also important. Nothing inside the tank must make it not a “clear view” for the sensor to measure the fluid level all the way down to the bottom.
If you want, you can put a silicone string around the edge of the sensor to strengthen the attachment. We do not recommend using two-component glue to attach the sensor.

Guide 2

Installation on metal tanks

You must have a hole in the tank wall at least 44 mm in diameter for all kinds of metal tanks. Gobius C can’t measure through metal walls. Many tanks have “standard” holes for internal level indicators, like Wema and compatible level indicators (KUS, VDO, Biltema…).

Standard hole, 1,25″ SAE 5
You must unscrew the other level indicator to mount our sensor but keep the bracket in the tank.
With our Adapter (ordered separately), you can use the bracket on the tank and mount the sensor. If you have long screws in the bracket, you should change to short ones. Long screws can interfere with the measurement.

  1. Find a place not too close to an edge; the minimum distance is 35 mm from the edge of the sensor to the edges of the tank
  2. Replace the screws in the bracket
  3. Remove the protective paper from the tape
  4. Put the sensor on the adapter and screw it down by hand; not too tight
  5. Wait 15 minutes for the tape on the adapter to harden

You need at least 90 mm of free space above the tank for mounting the sensor. This free space includes the adapter.
This is also important. Nothing inside the tank must make it not a “clear view” for the sensor to measure the fluid level all the way down to the bottom.

Guide 3

Connect to a power source, 12-24 Volts

Later in this instruction, you will see how you set up the sensor precisely for your need. Use the black wire to  – connector and the red to +. (If you do the opposite, no damage occurs.) The red lamp on the top of the sensor will light solid when it’s connected to power. Later on, the lamp will flash when the sensor is measuring.


Analog cable
NMEA 2000 cable

Guide 4

Integrate with control systems and external devices

With Gobius C, you can integrate the sensor with other systems. In addition to seeing the exact level on your phone, you can see the current status of external instruments and your control system. The table and the illustration show all possibilities.

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Analog outputs, wiring diagram

Red Black White Grey Brown Green Yellow Blue

Power (12-24 V) +


Power (12-24 V) –


Output 0-5 V


Current loop, 4-20 mA –


Current loop, 4-20 mA +


Alarm 1


Alarm 2


Resistive out, 10-180 / 240-33 Ohm


Download here a detailed description of all outputs.

Guide 5

Setup the sensor

Now the last part remains to start using your new tank sensor. You must now specify which liquid, tank geometry, tank depth, volume, etc., apply to your tank. You can also specify which alarm levels (in %) should be used, as well as if you intend to connect the sensor to an external gauge or control system, i.e., which signal the sensor should be set to (10-180/240-33 Ohm, 4-20 mA or 0-5 Volts.

Please download the app from App Store or Google Play

The automatic calibration is done for the sensor to learn the characteristics of your tank. This is needed during a new installation but also at other times. Your app always reminds you when needed.

Very important for the Calibration
The calibration aims to measure radar reflections from static objects near the Gobius C sensor. During the calibration, the distance from the top of the tank to the liquid level in the tank must therefore be greater than 150 mm (6 in).


Never overfill your tank

Overfilling your tank for all liquids, especially petrol, and diesel, is never good. Therefore, be careful when you see on your phone or on an analog instrument that the tank is about to be 100% full. In Gobius’ world, 100% full is 60 mm from the top of the tank. This is to help you not overfill your tank, i.e., you get a safety margin you should not exceed.