Patent ID: 8852421

Claim:
A method of utilizing a legacy controller with an oxygen sensor to control a reaction, comprising: locating said oxygen sensor in a reaction chamber, said oxygen sensor having an output, said sensor output being a voltage between 0 volts and 10 volts; attaching the output of said oxygen sensor to an interface module; using said oxygen sensor to monitor said reaction; providing a legacy controller having two leads and a voltage source, where a polarizing voltage of 600 mV to 800 mV is created by said legacy controller between said leads using said voltage source, and where said leads are in electrical communication with said interface module; using a circuit on said interface module, to convert said sensor output to a first digital value indicative of said sensor output; using a processing unit to create a second digital value from said first digital value; creating an analog voltage, based on said second digital value, said analog voltage indicative of a current to be provided to said legacy controller between said leads; using said analog voltage to create an output voltage to be applied to a gate of a FET transistor, wherein said FET transistor comprises two other terminals disposed between said two leads, such that current between said leads flows through said FET transistor, and wherein said current through said leads is determined by said output voltage; creating a current, in the range of 0 to 100 nA, between said two leads, by applying said output voltage to said gate of said FET transistor; and utilizing said legacy controller to control said reaction.