Abstract: The process for freezing cell suspensions by locating the suspension in a freezing chamber and simultaneously monitoring the temperature of the suspended cells and of the chamber. The cooling of the chamber is regulated at predetermined rates in response to give temperature levels of the sample. The cooling chamber includes a fan, a heater, and a source of refrigerant. The process includes the steps of selectively decreasing and increasing the temperature of the freezing chamber responsive to predetermined temperature points on the freezing curve of the cell sample.

Abstract: An automatic microprocessor-based control system for a diffusion furnace in which the controller is dedicated to a single associated diffusion tube to provide all monitoring and control functions necessary for a variety of diffusion processes. The controller provides direct digital control of time, temperature and gas flow, and can be readily operated with a variety of control algorithms.

Abstract: A plastic extruder system having a barrel and a shell with heat exchange elements surrounding the barrel is disclosed. Two thermocouples are provided, one for sensing the temperature of the inner surface of the barrel and the other for sensing the temperature of the shell. A system controller, into which a desired barrel setpoint temperature can be set and stored, receives and stores the independent temperature signals from the thermocouples and controls the heat exchange elements to automatically maintain the temperature of the extruder barrel close to the desired barrel setpoint temperature.

Abstract: A thermostat monitoring and controlling the temperature of produce ripening within an enclosure and featuring a bridge circuit sensing errors between the actual and desired temperatures in which the desired temperature is selected directly in units of degrees. A bridge amplifier having feedback maintains the bridge in electrical balance to avoid errors due to changes in bridge component self heating. An error detection circuit having a single control simultaneously selects upper and lower error limits centered on the desired temperature, in units of degrees. The circuit indicates whenever the actual temperature goes outside these limits. An alarm circuit indicates a temperature error or a power failure in the thermostat at the thermostat and at a remote location. This circuit utilizes an alternating current source which activates current direction-dependent indicators operating on alternate half cycles.

Abstract: A control circuit for a solar energy heating system comprising a pair of thermistors connected in series across a source of electrical power and respectively disposed to be responsive to fluid temperature in a solar collector and in a storage tank. A negative feedback high frequency oscillator which includes a Schmitt trigger is connected to the junction of the thermistors and provides a high frequency control signal having an amplitude which varies as a function of the temperature differential between the collector and tank. An electronic switch energizes a fluid pump for transporting fluid from the solar collector to the tank when the temperature at the collector exceeds that at the tank by a preselected amount.

Abstract: Blood cells, blood marrow, and other similar biological tissue is frozen while in a polyethylene bag placed in abutting relationship against opposed walls of a pair of heaters. The bag and tissue are cooled with refrigerating gas at a time programmed rate at least equal to the maximum cooling rate needed at any time during the freezing process. The temperature of the bag, and hence of the tissue, is compared with a time programmed desired value for the tissue temperature to derive an error indication. The heater is activated in response to the error indication so that the temperature of the tissue follows the desired value for the time programmed tissue temperature. The tissue is heated to compensate for excessive cooling of the tissue as a result of the cooling by the refrigerating gas. In response to the error signal, the heater is deactivated while the latent heat of fusion is being removed from the tissue while the tissue is changing phase from liquid to solid.