A NEW IMPLANTABLE MICROPROCESSOR CONTROLLED LONG DISTANCE TELEMETRIC DEVICE FOR CONTINUOUS MONITORING OF ANIMAL ACTIVITY AND TEMPERATURE

Ben Geeraerts(I), Mans Jansen(II) and Robert Puers(I)
(I) Katholieke Universiteit Leuven, Departement Elektrotechniek,
ESAT-MICAS Kardinaal Mercierlaan 94, 3001 Heverlee, Belgium
(II) IMAG-DLO, Postbus 43, 6700 AA Wageningen, The Netherlands

INTRODUCTION : In the field of animal monitoring there is a great need for intelligent and versatile devices for continuously collecting activity and temperature data of the animal without hampering of the animal and elaborate setups. Hence, the data should be transmitted by means of a "long distance" RF-link to a central personal computer which collects and processes the data. The device described in this paper fulfills all the above criteria.

TECHNICAL DESCRIPTION : The new device is contained in a glass, laser-sealed cylinder with an external diameter of 17 mm and length of 104 mm. A battery with an energy storage capacity of 1000 mAh powers the two dedicated thick film hybrids with the custom built electronic circuitry. The device can continuously monitor the animal and collect data for up to 1 month, depending on the monitoring window parameters.

The first hybrid is built around the Motorola 68HC11 microprocessor and can store activity and temperature data in a non-volatile 2 kilobyte EEPROM. A piezo-resistive accelerometer is used to sample the activity of the animal. User-defined movement detection algorithms are stored in a 32 kilobyte EPROM for processing of the raw accelerometer samples. A calibrated thermistor provides the temperature data. A low-power timing circuit is responsible for waking up the microprocessor at the appropriate user-controlled time-intervals and limiting of the overall power drain.

The second hybrid consists of a Frequency Shift Keying transmitter with a carrier wave of 30.025 MHz. This is used when stored and processed data is transmitted to the receiver-unit connected to the central personal computer. A Manchester-encoded bitrate of 2 kilobaud can be achieved over distances up to 10 meters, depending upon the external Electro-Magnetic Interference. The transmitter coil is put around the 2 closely stacked thick film hybrids.

CONCLUSIONS : The new implantable device can continuously provide valuable activity and temperature data of an animal in many practical and research situations. For example, the device is being tried out for the oestrus detection of sows. The "long distance" wireless link and user-definable timing parameters and movement detection algorithms will prove to be a very valuable asset of this device indeed.