Abstract: A temperature control system used to precisely and accurately control the temperature of a fluid stream in an analytical system designed for investigation of the chemical constituents of the fluid stream. One example of use is in chromatography such as for the chromatographic column in an amino acid analyzer system. The temperature control system utilizes a set of thermoelectric modules to transfer heat between a thermoconductive block which holds the chromatographic column and an air exchange heat sink which obtains heat from or disposes heat into ambient air as required. The control system regulates the temperature at a very rapid rate in order to minimize the recycle time of the instrument.

Abstract: A variable slip drive system for driving a variable speed induction motor. The system includes a tachometer for providing a signal proportional to the speed of the motor and a slip oscillator. The output of the tachometer and slip oscillator are combined by a motor drive oscillator to provide a motor drive signal. The frequency of the motor drive signal equals the tachometer signal, less the frequency of the slip signal. The motor drive signal is converted into a proportional, three-phase, high power signal for powering the motor. The frequency of the slip signal is controlled so as to be proportional to the motor speed as a means of optimizing the motor's performance.

Abstract: A method and apparatus for monitoring flow rate through a conduit. A flow number indicative of the flow rate of a liquid through the conduit is compared with a preselected reference number. The actual liquid flow through the conduit provides a clocking signal which determines the time span during which a count signal, indicative of the intended flow rate into the conduit, is accumulated thereby providing the flow number.

Abstract: A closed-loop drive system for variable speed induction motors for maintaining a constant slip frequency, regardless of motor speed. A slip frequency oscillator generates a signal having a frequency proportional to the desired slip of the motor and a tachometer generates a signal having a frequency proportional to the actual rotational speed of the motor. The stator frequency is the sum of the rotor speed and the slip frequency during acceleration and the difference between the rotor speed and the slip frequency during braking. Exclusive OR gates are used to add the slip frequency signal either to the tachometer signal or to the stator signal, the outputs of the gates being applied to a digital phase detector. The phase detector drives a voltage controlled oscillator which provides the stator signal. The output of the voltage controlled oscillator is used to trigger the slip frequency oscillator to prevent overlap of pulses to the digital phase detector.

Abstract: In an overspeed protection system for a centrifuge apparatus of the type including a rotor driven by a drive motor, a transducer for providing a signal whose frequency is a function of the rotational speed of the centrifuge rotor, an oscillator for generating a reference signal having a predetermined frequency, means for mixing the rotational speed signal with the reference signal to provide a difference frequency signal, a filter coupled to the output of the mixing means for passing signals having frequencies below a predetermined frequency, and means coupled to the filter for disconnecting power to the drive motor in response to an output signal from the filter, there is disclosed an improvement comprising a frequency comparator responsive to the rotational speed signal and the reference signal for generating an overspeed signal when the frequency of the rotational speed signal exceeds the frequency of the reference signal, and means for combining the outputs of the filter and the frequency comparator at th

Abstract: A light beam is passed through a cuvette, through which flows liquid to be analyzed optically for concentration of color reacted amino acids. The emergent beam is directed through a series of dichroic beam separators and pass band filters to produce three beams of substantially three different wavelengths. Photoelectric detectors produce electrical signals corresponding to each of the three wavelengths. Two of the signals are characteristic of the substance to be detected. The third is subtracted from the other two wavelength signals to produce a pair of output signals from which base line noise has been substantially eliminated.