Telemetry Transmitters

Sonotronics telemetry transmitters use a variety of sensors to provide real-time information about the environment experienced by the tagged animal. Coded ultrasonic emissions are detected and interpreted by either active or passive receivers within range. The 3 most common sensors and their use is described below:

  1. Temperature
    Temperature is most common environmental sensor used in fisheries research. By default, this sensor is encapsulated along with the electronics that control the transmitter, and as such has a small amount of “thermal mass” that acts to smooth small thermal changes. It should be noted temperature as an indication of predation by aquatic mammals because of their higher than ambient body temperature, or as a surrogate for depth when the temperature of the local water column is well known. Behaviors such as migration and spawning may also be predicted by monitoring localized temperatures. Data is reported in either degrees Fahrenheit for PPM coded tags, or as degrees Centigrade for ACT coded tags, with accuracy and resolution of 1 degree F or 0.5 degree C respectively.
  2. Depth (pressure)Depth tags use an absolute pressure sensor to measure the combined weight of water and atmosphere directly above the transmitter. When first activated, these tags measure the ambient conditions to establish a surface point, usually at sea level. Once immersed in water, subsequent measurements subtract the effect of atmospheric pressure, leaving only the effect of the weight of tag (depth). While pressure sensors can provide very accurate readings, it is important to understand factors that can affect the conversion of pressure to depth. For example, tagged animals in alpine lakes should have their transmitters initialized (using the included magnets) to allow the lower air pressure to be measured for a surface value. By default, Sonotronics Depth Tags report actual pressure in units of pounds per square inch and allow conversion from pressure to depth after data is logged on the local receiver.  Conversion formula based on use in fresh water and salt water are provided to ensure best possible accuracy.  Default resolution of 1PSI, with full scale values of 100 PSI for ACT coded tags, and 200 PSI for PPM coded tags allow for sensing of depths up to 230 feet and 461 feet of water respectively, with an accuracy and resolution of 2 feet.  It should be noted that attempting to use higher resolution than 1 PSI need to consider sources of error – normal variations of atmospheric pressure is 0.5PSI, increasing during severe storms, and wave heights more than 1 foot also can result in local variations of over 0.5PSI. For sea water, the conversion from PSI to depth in feet is:

 

3.Accelerometer (activity)
Accelerometers offer a wide range of application based on the algorithms used to assess multiple reading of these sensors.  Sonotronics transmitters use 3-axis accelerometers and by default are set to measure values of +/- 8g with 12-bit resolution, resulting in a maximum resolution of 3.9mg prior to any processing. When used to determine activity, these sensors are set to filter the effects of gravity based on position relative to earth center, and obtain dynamic values based on movement.  Typically multiple samples of each of the 3 axis (x,y,z) are obtained and arithmetic algorithms are performed to provide a single value that may indicate an indication of activity such as feeding, migration, spawning, and evasion. As an example, a common method for determining activity is setting the transmitter to take 16 samples at a rate of 1.6 sample per second, then applying a formula for an RMS value of these samples in the form:

 

Various Telemetry Tags

Sonotronics produces a variety of transmitters which provide near real-time environmental data for collection by either active tracking receivers or by passive logging receivers or both.  Although other models are available that make use of accelerometers and more exotic sensors, standard transmitters report temperature or depth data.  Coded Temperature Tags, Pico Temperature Tags, and Itty-Bitty Temperature Tags provide better than 1 degree C accuracy from -4C to +45C, with a resolution of 0.5C (higher resolution for metabolic studies is available upon request).  Depth Tags and Itty-Bitty Depth Tags indirectly provide depth information by measuring pressure, or weight of the water column directly overhead.  Nominal full scale pressure of 100PSI is provided, however values from 50PSI to 435PSI are available (35m to 300m+) with a resolution of 1% of the chosen full scale value.

MODEL 3 Length OD WT in H20 Range1 Autonomy2
Temperature Sensing Tags
CTT-83-2-I 53mm 15.6mm 9g To 1km 14 months
CTT-83-2-E 54mm 15.6mm 9g To 1km 14 months
CTT-83-3-I 63mm 15.6mm 10g To 1km 36 months
CTT-83-3-E 64mm 15.6mm 10g To 1km 36 months
Depth Telemetry Transmitters
DT-97-L 80mm 15.6mm 11g To 3km 12 months
Miniature Temperature Sensing Tags
PTT-1 21mm 7.1mm 1.0 500m+ 7 days
PTT-2 24mm 7.1mm 1.2 750m+ 12 days
PTT-3 24mm 7.8mm 1.2 750m+ 21 days
IBTT-08-1 27mm 8mm 1.6 500m+ 21 days
IBTT-08-9-I/E 52/55mm 11mm 4.2/5.2 750m+ 9 months
Miniature Depth Telemetry Transmitters
IBDT-97-1 30/35mm 9.5mm 1.6g 500m+ 20 days
IBDT-97-2 37/42mm 9.5mm 2.5g 500m+ 45 days
Notes
  1. Range is typical under good conditions, using a Sonotronics active receiver and directional hydrophone.
  2. Autonomy based on a ping rate of once per second, and telemetry reading approximately 3 times per minute.  Extened lifetimes are available by cycling the transmitters, please contact Sonotronics for more details.
  3. -E is the extension denoting external mount, -I denotes internal implant. Please specify internal or external when ordering transmitters.

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