Abstract: Method and apparatus for calibrating a gamma counter, such as a fibrinogen monitor, employing a pulse-height analyzer and a control circuit to determine the optimum high-voltage setting on the photomultiplier tube of a scintillation counter. A first pair of upper and lower pulse-height levels are automatically selected and counts measured to determine if the spectrum of the radioactive source is positioned correctly in the pulse-height domain. A series of measurements are made with differing high-voltage settings to ascertain the desired location of the spectrum. A second pair of upper and lower levels is provided for use in the actual monitoring operation and is automatically set after each calibration operation.

Abstract: A background subtractor circuit is disclosed for subtracting a preselected number of pulses from a train of input pulses. Switches are provided whereby the operator selects the background pulse rate, attributed to environmental factors, and wherein a train of background pulses are subtracted, at a preselected rate, from the incoming pulse train.

Abstract: A method and apparatus for measuring or testing static and dynamic coefficients of friction. The frame of the apparatus is held fixed with respect to the test surface, and a friction pad, mounted on the frame and capable of moving relative to the frame, also rests on the test surface. A torque is developed in the friction pad, through the means of a fluid bed, and the resulting relative movement between the test surface and the friction pad is sensed. Also disclosed are mechanisms for setting the normal force which the friction pad exerts on the test surface, for adjusting to misalignments and small surface irregularities without deleterious effects, and for regulating the torque developed in the friction pad.

Abstract: Disclosed is an automatic sample changer for sequentially operating on a plurality of samples housed in test tubes, circulated around a continuous track, and sequentially associated with a radiation counting device by way of an elevator mechanism. The continuous track is in modular form, and is designed, respectively, to accommodate fifty, one hundred, two hundred or three hundred samples. Rotating index wheels are employed to drive the samples around the track, with several index wheels being used for the longer tracks. The motors controlling the respective index wheels are reversible, and when more than one motor is employed, the motors may be operated in parallel.Also disclosed is a mechanism for loosely coupling the index wheels to their associated motors to facilitate repair and ensure accurate alignment with the plane of the continuous track.

Abstract: An automatic sample changer particularly suited for use in counting biomedical samples from in vitro tests using radiopharmaceuticals such as the technique of radioimmunoassay. A plurality of samples, such as gamma ray emitting samples housed in test tubes, are automatically circulated around a continuous track and are sequentially associated with a radiation counting device by way of an elevator mechanism. A single rotating driving wheel is effective in moving one hundred samples independently travelling on the continuous track. Also disclosed is a breakaway safety mechanism associated with the elevator, and means for detecting and signaling jams in the track and elevator.