Abstract: A temperature control system for monitoring and controlling a zone supplied with low-pressure steam is disclosed. The system utilizes a series of balanced Wheatstone bridges to provide a variety of automatic and manual control techniques to maintain temperature in the zone. Means are also provided to obtain direct readings of temperature, rate at which heat is being supplied, and the position and movement of a steam control valve which is utilized as a heat metering apparatus. The bridge leg outputs are permanently connected by high impedance coupling circuits which act as voltage dividers to obtain the required resultant control signals. High impedance coupling eliminates the need for control circuit balancing, thereby minimizing required calibrations in actual field use. The sole balancing calibration is with each sensor leg to a centered bridge leg.

Abstract: A temperature control system for monitoring and controlling a zone supplied with low pressure steam is disclosed. The system comprises a series of balanced Wheatstone bridges which, when calibrated, provide a variety of manual and automatic control conditions to maintain the temperature in the zone. Means are provided for obtaining direct readings of room or zone temperature, and monitoring the position and movement of a steam control valve which is utilized as the heat metering apparatus. In order to compensate for environmental differences which may exist in various zones under control, there is disclosed apparatus for selectively varying the effect of sensors utilized in the system, and in particular, the effect of a resistance thermometer located within the zone which may be subject to variations in accuracy in terms of placement.