Apparatus and methods for providing fluid such as water at a controlled temperature. In some embodiments, hot and cold fluid is provided to a thermostatically controlled mixing valve, which then provides fluid at a mixed temperature to a plumbing system. The thermostat provides a first loop for closed-loop control of fluid exit temperature, and preferably there is a second, electronically controlled closed loop for adjusting the temperature of fluid exiting the valve. In yet other embodiments the electronic control loop is fail-fixed, such that a loss of electrical communication to the actuator results in the actuator maintaining its last position. In yet other embodiments there is a system including a flow sensor and a recirculation pump such that the temperature of the fluid exiting the valve cannot be adjusted if there is insufficient flow, or if the pump is actuated.

A brazing system has a first gas source, a second gas source, an enclosure, a brazing torch, and a control system configured to control a ratio of the first gas source and the second gas source.

A brazing system has a first gas source, a second gas source, an enclosure, a brazing torch, and a control system configured to control a ratio of the first gas source and the second gas source.

Apparatus and methods for providing fluid such as water at a controlled temperature. In some embodiments, hot and cold fluid is provided to a thermostatically controlled mixing valve, which then provides fluid at a mixed temperature to a plumbing system. The thermostat provides a first loop for closed-loop control of fluid exit temperature, and preferably there is a second, electronically controlled closed loop for adjusting the temperature of fluid exiting the valve. In yet other embodiments the electronic control loop is fail-fixed, such that a loss of electrical communication to the actuator results in the actuator maintaining its last position. In yet other embodiments there is a system including a flow sensor and a recirculation pump such that the temperature of the fluid exiting the valve cannot be adjusted if there is insufficient flow, or if the pump is actuated.

A system is configured to generate a pressurized flow of gas comprised of a first gas having a partial pressure that varies in a predetermined manner. This may be used, for example, to simulate a previous and/or theoretical respiratory gas flow that was produced (or could have been produced) by a subject. The system is configured to deliver the pressurized flow of gas to a testing system configured to measure the partial pressure the first gas in flows of gas. This may provide an opportunity to determine the response of individual testing systems to various clinical circumstances.

A brazing system has a first gas source, a second gas source, an enclosure, a brazing torch, and a control system configured to control a ratio of the first gas source and the second gas source.

Apparatus and methods for providing fluid such as water at a controlled temperature. In some embodiments, hot and cold fluid is provided to a thermostatically controlled mixing valve, which then provides fluid at a mixed temperature to a plumbing system. The thermostat provides a first loop for closed-loop control of fluid exit temperature, and preferably there is a second, electronically controlled closed loop for adjusting the temperature of fluid exiting the valve. In yet other embodiments the electronic control loop is fail-fixed, such that a loss of electrical communication to the actuator results in the actuator maintaining its last position. In yet other embodiments there is a system including a flow sensor and a recirculation pump such that the temperature of the fluid exiting the valve cannot be adjusted if there is insufficient flow, or if the pump is actuated.

A brazing system has a first gas source, a second gas source, an enclosure, a brazing torch, and a control system configured to control a ratio of the first gas source and the second gas source.

A brazing system has a first gas source, a second gas source, an enclosure, a brazing torch, and a control system configured to control a ratio of the first gas source and the second gas source.

A brazing system has a first gas source, a second gas source, an enclosure, a brazing torch, and a control system configured to control a ratio of the first gas source and the second gas source.