An AT-type microcomputer with a resident 16-channel, 12-bit A/D board is used to measure and store signals from freely moving rats in a sleep-deprivation study. The computer acquires brain temperature signals from small, glass-encapsulated thermistors. The calibration values for each thermistor are stored in a separate calibration file and loaded into the program when it is started. A thermistor bridge circuit accommodates a tolerance of q20% in the nominal thermistor resistance, and covers a range of 25~ to 45~C with 0.01~C resolution and 0.04~C accuracy. The system also acquires a """"""""core"""""""" or peritoneal temperature, using small RF transmitters that change frequency with temperature. The transmitter system is capable of 0.02~C resolution with 0.07~C accuracy. Custom software controls the sample acquisition rate, filtering linearization, calibration, and storage of the temperature signals. In addition to the temperature signals, the computer also acquires 2 EEG signals and an EMG. The custom software uses a weighted combination of these signals to determine the animal's sleep state, which can then be correlated with the temperatures. The system also has a provision to acquire the heart rate, but that feature has not yet been implemented. The A/D card runs in a """"""""background"""""""" mode for 30-second intervals, with the data transferred directly to a specified memory location. This mode of operation frees the CPU for processing the previous interval's data and allows uninterrupted, or continuous, data acquisition. To reduce calibration errors in the transmitter temperature system, a computer-controlled water bath calibrator was developed that performs an automatic 3-point calibration of the transmitters to within 0.04~C. The use of this calibrator improved the transmitters' accuracy from 0.22~C to 0.07~C.
