The Thelma Biotel tilt sensor transmitter deliver high-resolution data in the tilt range 0 – 180° along the central axis as a default.


  • Available in all transmitter sizes 6, 7, 9, 13 and 16
  • Long operational lifetime ~ 3 months – > 10 years

The inclination sensor is embedded into the transmitter and measures the tilt angle along the central axis of the casing.

Thelma Biotel offers the smallest inclination sensor acoustic transmitters on the market. It can be delivered down to 6.3 mm in combination with other sensors, such as temperature and depth, with several months of operational lifetime.


Animal behaviour connected to the angle of the individual, such as resting or diurnal migration, is a valuable application for the transmitter containing the tilt sensor.

The transmitter containing the tilt sensor can also record angular measurements of the anchor lines used for anything from wharves to oil platforms. It can be helpful to keep track of the tilt of the anchor points in order to prevent uneven pressure in one location. It is also possible to use the tilt sensor for volume measurements of net bags in fish farming facilities and to keep track of the angle of deployed equipment on the lake – and seabed.


Standard measurement for tilt is a point measurement taken right before the data is transmitted. This means that the measurement frequency will be linked to the transmit interval. Always check your delivery note to ensure you apply the correct calculation when converting measurement data to unit of choice. The method may vary due to different data ranges and set-ups.


There is a variation of measurement modes available upon request. Some modes can include longer or shorter measurement intervals, proportion of last day the measurements have been more or less tilted than a baseline, or Max / Min / average. Do not hesitate to contact us for more information regarding your project.

Using a magnet command, the angular zero point may be set to change the default orientation or compensate for misalignment after mounting the tag.

Method for resetting the zero reading of the tags:

Keep a receiver close by the transmitter in order to catch the transmits. Make sure you turn the tag on, and it is running. Hold the magnet key to the transmitter, to activate the magnet sensor again. The transmitter will emit a series of quick pulses, seen as flashing light at the receiver, and the receiver LED will switch to white light. The quick flashes will be followed by 1o pings at 1 Hz. Keep the magnet to the tag for the entire sequence of pulses and then 7 more seconds after the last, tenth flash is seen. The magnet can now be removed and the transmitter should be held in the orientation which should read zero degrees. There is a window of about 3 seconds from the magnet is removed to the transmitter should be in position. Hold the tag stable and correctly oriented for minimum 10 more seconds. After about 100 seconds wait, the tag will start to emit standard transmits with data again. This should now read zero or close to zero if the transmitter has shifted slightly after reprogramming.