Digital electronic steam humidifier control

Abstract

Disclosed herein is a method and a digital electronic steam humidifier control for use with a humidifier system including an electrode boiler to provide a normally repetitive fill, boil, fill-on-drain cycle. The humidifier control includes circuitry for providing an analog signal proportional to the electrode current, and a comparator network which receives the analog signal and a reference voltage and scaled voltages provided by additional circuitry to establish predetermined levels of electrode current at which the control responds. The comparator network provides a plurality of digital outputs having a high or low state depending upon the magnitude of the electrode current, which outputs are coupled to logic circuitry including NAND gates and which operates to actuate electrically controlled fill and drain valves to vary the water level so that the electrode current varies between predetermined lower and upper current limits, and which also operates to temporarily cut off the power to the electrodes if the electrode current exceeds a predetermined over-current limit. The logic circuitry also operates in conjunction with high water probes to prevent overfilling of the boiler and to cause boiling of the water without draining during start up so that the water acquires a predetermined higher level of conductivity so that the electrode boiler operates efficiently. An abnormal operation light and high and low current indicators are also provided to inform an operator of the status of operation of the control.