Flowmeter-controlled valving

Abstract

An electrically-actuated fluid-flow control valve employed to establish and maintain prescribed flow conditions with the aid of a fast-response flowmeter is caused to operate swiftly, accurately and reliably by way of unique electrical circuitry which selectively enhances responses to low-level signals and cooperatively induces electromechanical oscillations offsetting hysteresis of the valve armature suspension. In a preferred context of a system wherein a thermal flowmeter is used to actuate a solenoid valve and thereby cause actual flow conditions to agree with those prescribed by operator-controlled settings, normal sluggishness of responses to low-level electrical signals is overcome by circuitry which under appropriate circumstances automatically exercises logic to command that the valve be disproportionately energized to effect immediate strong action which will reliably and quickly bring about intended and accurate change in flow. Within the valve itself, where unavoidable hysteresis associated with the spring suspension for the armature would otherwise tend to interfere with precision of control, corrective mechanical armature oscillation is advantageously induced at a suitable fixed ripple frequency at the same time that a pulse-type excitation circuit delivers variable-duty-cycle control output to the valve.