Transmitters
Sonotronics manufactures ultrasonic transmitters that attach to equipment or animals for detection and tracking with compatible receivers. Transmitters are defined by three main variables: size, autonomy or operating life, and detection range. They emit coded signals that uniquely identify the attached object; the coding protocol is selected based on the receiver system and tracking method. Each transmitter operates at a production-set frequency chosen for environmental conditions and receiver compatibility. The following sections provide additional detail based on the object being tracked.
Sonotronics manufactures transmitters for tagging and tracking a wide range of aquatic species, typically for studies with defined objectives. The most important factor in selecting a fisheries transmitter is the smallest animal to be tagged. According to Fisheries Techniques, a transmitter’s weight in water should not exceed 1.25% of the animal’s weight out of water. Because Sonotronics lists transmitter weight in water, multiplying that value by 80 gives the minimum recommended animal weight. Tracking duration is the next key consideration because it affects both attachment method and transmitter protocol. For example, a one-month active tracking study from a boat may use a simple externally mounted transmitter with an ACT “continuous” protocol. By contrast, a study using only submerged passive receivers should use surgically implanted transmitters with a PPM coded protocol, which can extend transmitter life to nearly ten times that of a continuous protocol. Once size and operating life are defined, the expected detection range can be evaluated. These factors can be adjusted iteratively to identify the best transmitter; for instance, if the body of water limits detection range, selecting a transmitter for a larger minimum animal size may provide longer autonomy.
“Recover Your Assets”
Sonotronics is the leader in transmitter development for a variety of oceanographic needs. Our transmitters have been used to relocate current meters, ROV/AUV/UUV vehicles, deep ocean sites, divers, and many other subsea applications.
This page provides an overview of our equipment marker pinger product line. Links to specific pages about products are found here.
Equipment Marking Transmitters (EMTs) are similar to fisheries transmitters but use rugged housings with mounting features for quick, secure attachment to underwater instruments, vehicles, or structures. They are generally used to help recover valuable equipment when underwater conditions prevent normal retrieval. EMTs are typically selected by first determining the required service life, then choosing the desired detection range for the deployment environment. For example, an ADCP planned for a two-year deployment may benefit from a medium-range four-year transmitter, while an AUV with an expected one-month mission may be better suited to a shorter-life transmitter with a longer detection range. EMTs are usually tracked actively and commonly use the ACT protocol for continuous transmissions.
Sensors
Sonotronics transmitters can also include integrated sensors that telemeter local environmental data to a remote receiver.
Temperature sensors report the current water temperature in degrees Fahrenheit or in increments of 0.5 degrees Centigrade.
Pressure sensors report the instantaneous pressure from the water and atmosphere above the sensor in pounds per square inch (PSI). This value can then be converted to units of length using a simple linear formula.
Accelerometers provide raw movement data along three axes, which can be converted into values such as Overall Body Dynamic Acceleration (ODBA), general activity index (GAI), and tilt angle relative to gravity. ODBA and GAI are used mainly to assess fish physiology, while tilt angle is used to monitor underwater equipment, such as ADCPs, that must remain near vertical to function properly.
ORDERING INFORMATION
The following is a guide to the many possible variations and configurations of sensors for fisheries transmitters, note not all combinations are possible:
Sensor Choices
__Temperature __Pressure (depth) __Acceleration
Transmit Protocol
__ACT __SR1 __SR6 __Ops
Burst Interval (time between complete protocol transmission)
__Continuous __15 Sec __ 30 Sec __ 60 Sec __ Other
Full Scale Values
Temperature __127F __ 40C
Pressure __ 50PSI __ 100PSI __ 200PSI __ Other
Acceleration __ 3.44m/ __ Other
Sensor Specific Values
Accelerometer
Derivation __ VeDBA __ ODBA __ SDM __ Other
Sample Frequency __1.6 Hz __ 12.5Hz __ Other
Sample Size _16 _32 _64 _128 _256 _Other
<***> table of transmitters with pics of IBDT (showing sensor), graph of depth, EMT-AR
ACCELEROMETER BASED ACOUSTIC FISHERIES TRANSMITTERS
Sonotronics AT transmitters use an integrated 3-axis accelerometer to measure and transmit derived activity and movement parameters for a tagged animal. Unlike pressure or temperature sensors, meaningful activity measurements require multiple acceleration samples from each axis, which are then processed using a formula to produce a usable value. Two commonly used measures of movement and energy expenditure are VeDBA (Vectorial Dynamic Body Acceleration) and ODBA (Overall Dynamic Body Acceleration). Another configuration reports the sum of the maximum values of dynamic acceleration of each axes during a sample period (SMD).
VeDBA
VeDBA represents the magnitude of the dynamic acceleration vector and is calculated from the RMS value of ‘N’ dynamic acceleration samples from the x, y, and z
axes where are sampled instantaneous values of the accelerometer are sampled, high pass filtered to remove the effects of gravity.
One advantage of VeDBA is that it is relatively insensitive to the orientation of the transmitter implanted in the study animal.
To maximize transmitter life, the accelerometer controls the sampling interval. The nominal sampling rate is 12.5 Hz, or 12.5 samples per second. The selected number of samples determines the sample interval and must be a binary value between 16 and 256. For example, at 12.5 Hz, a sample size of 256 results in a sample interval of 256/12.520.5 Seconds.
ODBA
ODBA is calculated by summing the absolute values of ‘N’ dynamic acceleration samples from the x, y, and z axes.
Although ODBA can provide a slightly better estimate of energy expenditure, it is more sensitive than VeDBA to the orientation of the implanted transmitter and is typically used in laboratory conditions.
SDM
SDM is calculated by summing the maximum absolute values of dynamic acceleration samples from the x, y, and z axes during a given period:
This value is helpful in comparing peak movements over multiple sample periods.
SCALE and RESOLUTION
Sonotronics transmitters report values from 0 to 255 using 8-bit resolution, so it is important to understand what each bit represents. For VeDBA measurements, a value of 1 corresponds to 1.38mg or 0.0135m/, and a full-scale value of 255*1.38mg ≈ 352mg ≈ 3.44m/. ODBA scaling should be selected carefully based on the sampling rate and sample size, because summed values can become large very quickly.
