MEASUREMENT OF TEMPERATURE
AND POSITION OF AN EGG IN THE
NEST BY TELEMETRIC SYSTEM

Paulo José Abatti, Sérgio Francisco Pichorim & Christian De Marino Fernandes
CPGEI / CEFET-PR - Paraná Federal Center of Technological Education
Av. Sete de Setembro, 3165 CEP : 80230-901 - Curitiba - Paraná - Brazil

INTRODUCTION This work describes a biotelemetry system for continuous monitoration of temperature and position of an artificial radio transmitter egg in a small bird nest.

METHODS The egg (dimensions: 38mm x 24mm, weight: 12g) is composed by a modified block oscillator working as a PPM circuit, with transmitting radio frequency of 400kHz. Temperature modulates the relative position of transmitted pulses[1]. Signal reception (through ellipsoidal coils placed externaly around the nest) is done by four antennas in quadrant, two by two combinated, in order to get the signal from any position of the transmitter in the nest. The receptor circuit is responsible to separate and process the informations of temperature and angular position (static and dynamic) of the egg in the nest. The informations are analised and stored by an IBM compatible PC connected to the receptor circuit through the parallel interface. The receptor is composed by an analog circuit that realizes arithmetic operation with the signal from the antennas. In addition, a 6-bit digital circuit (4 bits for the output position signal, 1 bit for the output temperature signal and 1 bit for the multiplex selection proceeding from the computer) is responsible for the logic operation with this signal and interface with the microcomputer. The software, developed in C language, processes, presents graphically and stores the received data for posterior analysis.

RESULTS The system has been submitted to extensively bench tests showing, for instance, that egg internal temperature can be measured in a 20 to 50°C range, resolution of 0.2°C, with an average error of less than 1%. Power consumption was about 0.12µW per transmitted pulse, and it was able to operate continuously over 1 month, using a miniature silver battery (Eveready n. 379). The egg position inside the nest can be mesured with a resolution of 22.5ş, because it is registered with 4 bits, presenting an average error of 1.6%.

DISCUSSION & CONCLUSIONS Tests in vitro showed the viability of the system in monitoring temperature and position of small bird's egg, and field tests will be done in the beginning of 1997.
[1] - Pichorim, S. F. and Abatti, P. J., "A temperature telemetry system based on a single transistor PPM transmitter with remote switching.", Biotelemetry XIII, 1995.