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Tenet Ultrasonic Fuel Sensor

The G120 (firmware 2.12 and above) supports the use of the Tenet UL212 fuel sensor. The sensor measures the fuel level height and the temperature of the fuel. When connected to a G120 via the RS232 port – the fuel level and temperature can be reported to the server in specified Analogues. 

Additionally, readings can be made while out of trip and a drop in fuel level can be reported in a specified Digital Input.


The sensor must be powered, and also connected to the RS232 port on the G120. Check the Tenet UL232 User Manual for more details.  


  • Sensor Red Wire -> Power supply (12V/24V) 

  • Sensor Black Wire -> Ground (any black wire on the G120) 

  • Sensor Yellow Wire (RS232 TX) -> G120 Violet, Pin 21 (RS232 RX)

  • Sensor White Wire (RS232 RX) -> G120 Black/White, Pin 22 (RS232 TX) 


The device is to be fixed below the fuel tank (externally) using adhesives and straps. Consult the Tenet UL232 User Manual for guidance. 

Parameter Setup

Add the RS232 function tab, and set the function to UL212 Fuel Sensor. 


Typical Operation 

Add the UL212 Fuel Sensor tab and Enable the sensor. 

Typical operation involves reading fuel level and temperature data and reported them to the server in the Analogues specified in (1) and (2). While in trip, the device will record the sensor value about once every 10 seconds.  

While in trip, new logs are not generated for these reads, but as the G120 generates other logs (i.e. the in trip 60 sec logs) – these values will be passed up to the server.  

To log fuel level and temperature data while out of trip, specify a log interval in (3). 

Fuel Theft Detection (Out of Trip only)

While out of trip, a drop in the fuel level between log intervals can be detected. Set an appropriate delta value in (4), this will depend on the size of your fuel tank, as well as the log interval out of trip (3) that was set. If the fuel level drops by the delta specified between two successive out of trip log intervals, the digital input specified in (5) will be set to 1 for this next log. An alert which is triggered by this digital input can then be set up on the end server. 

Set up in Telematics Guru

Once we have configured the device parameters in OEM server, set up in Telematics Guru is simply a matter of creating an I/O mapping - i.e. to label Analogue 16 as 'Fuel Level'. Additionally, we also need to convert the raw value into a human-readable format. 

To set up, we just create an asset, and go to the I/O mappings tab. 


Then we add analogue 16 (or whatever we have selected in our parameters to be the fuel level). 

  1. Select the analogue where the level is being reported (16 in this case)
  2. Name the analogue
  3. We may elect to use "General" if we just want to report the value in mm - but percentage may be more useful to us. If we have multiple types of vehicle, with varying size tanks, this standardizes the measurement.
  4. We need to set up the conversion factor, more on that below
  5. Leaving these ticked ensures that the value appears on the live view popup. 

Conversion Factor

The probe simply sends an ultrasonic beam to measure the distance from the bottom of the tank to the top of the fuel. So this gives us a 'level' - if we simply wanted to report this value in mm - we would set the conversion factor (4) to 0.1 - as the raw value is in mm x 10. How we can convert to a percentage is best explained by an example:

Conversion Example:

Our fuel tank is 1m deep (top to bottom) - the reading reported by the sensor is 5000 (raw) = 500mm. We know this means our tank is 50% full. 

So our equation to get the percentage at any time would be:

Reading ÷ Full tank value * 100 

i.e. for the above reading/10000 * 100.  (10 000 because 1000mm is reported as 10 000 as a raw value)

So our conversion factor is 0.01

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