When most researching biologists think of radio telemetry, they think tracking, locating, or maybe logging animal presence or absence. However, there are other tools available to the researcher which can expand the scope of their work and their research. The engineers at ATS have been working to bring these new tools and technologies to the forefront so that the research community can better understand animal behavior, and perform more meaningful research.

One often overlooked type of transmitter allows you to collect information you otherwise could not. It’s the ATS Precise Event Transmitter, or PET. This type of transmitter functions just as a standard one would, allowing you to track or monitor your subject study species normally. But using sophisticated microprocessor technology, additional data can be collected that can help you track and monitor when specific events have occurred. If you can identify it, we can measure it!

 

The theory of operation of the PET transmitter is straightforward, and it's easy to use in the field. Various sensors, or combinations of sensors, are imbedded within the standard VHF beacon transmitter. These sensors are interfaced to the on- board microprocessor. These sensors include, but aren’t limited to:

1) Temperature Sensor (a simple thermistor device)

2) Movement Sensor (or "tilt switch", a small metallic capsule containing 2 conductive spheres which allow current to flow when agitated)

3) Light Sensor (a silicon chip which detects the presence or absence of light energy)

4) Pressure Sensor (a stainless steel diaphragm)

These kinds of sensors provide an output signal to the microprocessor, which applies logic to that measurement, and determines whether a pre-defined condition exists or not. For instance, a certain amount of movement, change in temperature, or the presence or absence of light, within a specified time period can be sensed. Then, the elapsed time from a certain condition occurring is kept track of by the internal clock. The time increment, or resolution, is usually 30 minutes, but other values may be used.

Because a clock is built into the microprocessor chip, the time when a specific measurable “event” has occurred can be determined. The transmitter micro-controller is programmed to take measurements, and then convert the values into an audible “beep” sequence which can be heard by the researcher using a standard radio receiver.

To determine the various values being transmitted, the researcher may easily “decode” the beeps, and convert them into meaningful numeric data values. The beeps are transmitted once per minute by the transmitter, and the beep pattern, or pulse train, is transmitted within a ten second window.

The encoding of the value is of the 8 bit type. Using this convention, there are eight spaces within which a value may be derived, as follows:

Hearing a double beep within a certain “space” represents the number value associated with that space. Hearing a single beep represents no value for that space.  If the researcher hears a  double pulse in spaces d, f, and g, and a single pulse in the other spaces, the resultant value is then 16 + 4 + 2 = 22. You can see that the maximum value that may be transmitted is 255, by adding up the value for each of the eight spaces.

A typical PET might be transmitting a time value, and is usually programmed to have the resultant value equal to one half hour. Thus, a transmitted value of 19 would be equal to 19 half hour periods, or 9.5 hours.

In order for you to know when to begin listening for the beeps, there is a five second silence which begins the sequence – no pulses are emitted during this time. This silent sequence alerts you to listen for the next pulse train sequence. Additionally, two quick beeps are transmitted at the beginning and end of the actual pulse train containing the data pulses. It is usually helpful when listening to the pulse train to have a note pad available to help you count the pulses.

You can click on the icon and hear two sample pulse trains. Can you decode the pulses and determine the resultant value? The answer is at the bottom of this page.

Two big advantages of this simplified system of transmitting data values are: the additional power consumption is minimal, allowing transmitter life to be extended. Second, no special decoding equipment is necessary, such as a datalogger. All that is needed is the researchers ear!

There are many conditions or events that may be determined using PET transmitters; some of the common ones are outlined below. Remember that you may have a particular study which can measure these variables in just about any combination, since ATS can tailor a specific transmitter program for your requirements, for a nominal investment.

Temperature:

 A temperature sensor can be used to determine exact time of animal mortality, or of parturition (birth) using ATS' VIT, or Vaginal Implant Transmitters, equipped with PET temperature option (model M3900)  .  Here, the normal transmitter mode (VHF beacon only) is enabled whenever the current ambient temperature is above or below a predetermined threshold. The PET mode is programmed to be enabled if the temperature exceeds that threshold. In that case, the PET mode will then begin transmitting the elapsed time data every minute, and transmit the appropriate pulse train “packet” that represents the elapsed time since temperature threshold has been exceeded.

Another application allows the researcher to know the actual temperature of the transmitter. Here, the value transmitted must be translated using a lookup table (supplied by ATS) in order to gain the actual temperature reading. Simple temperature related “events” also can indicate mortality. Adding the PET option allows the researcher to know actual time since mortality.

Light:

 An ATS transmitter which includes a light detecting sensor can be used to determine the exact time an animal has entered hibernation or denning.

Movement:

The tilt, or activity, switch has many uses. Most commonly, they are used to indicate whether an animal is moving or not, hence indicating mortality. By adding the PET option, the actual time since mortality can be derived.

Another use involves the standard ATS Trap Transmitter (model M4000), the researcher can determine that the trap has been sprung, since a movement, or activity sensor, is incorporated into the tag. However, by adding the PET option, one can also determine the length of time since the trap has been activated.

Pressure:

A pressure sensor may be used to determine the depth at which tagged fish are located, or the altitude ranges of animals in a mountain habitat.

Conductivity:

 Conductivity sensors are used to measure the relative or absolute levels of salinity. One could easily determine whether a fish is in fresh or saltwater with this type of PET, and also the amount of time the fish has been in that condition.

In the end, the basic question that needs to be asked by today's researcher is “what event do I need to know?” There is a strong chance that a PET transmitter from ATS will help answer the question. Contact ATS to have us build a PET transmitter designed for your next study.