Calibration of computer-monitored running wheels with adjustable drag

The design of a rodent running wheel with adjustable drag and ability to measure accurately the direction as well as the speed of running is described. A computer program in the C language enables a single microcomputer to monitor several wheels simultaneously. Drag is conveniently calibrated by the rate of deceleration from 1 revolution per second when no animal is present, and the calibration procedure can also assess the smoothness of the drag mechanism. Results of tests of the setability, repeatablility, and durability of the drag are presented. A method is outlined to determine the physical work required to accelerate the wheel and to maintain its rotation against the frictional drag.