Digital electronic apparatus and casette sized for intravenous

Abstract

A crystal-controlled low-frequency power-conserving circuit for use in a controller operating with a casette to limit the rate of flow of an intravenous solution to a patient. The circuit uses a crystal oscillator operating below the stray frequencies often present in a hospital environment. The CMOS components in the circuit respond to the low frequencies of the oscillator, display no sensitivity to the higher stray frequencies, and consume a minimum of energy. Binary rate dividers reduce the frequency obtained from the oscillator by a positive integral power of two. Cascaded variable binary rate multipliers selectively permit the absorbtion of a least half of the pulses received from the rate divider. The inverted pulses of the binary rate multipliers pass to the S input of a D-type flip-flop. The pulses from the binary divider pass to the C input of the same flip-flop. On a pulse from the rate multiplier, the Q output of the flip-flop provides a positive pulse to a monostable multivibrator which then briefly turns on current to the coil of an electromagnet to allow fluid to enter the cassette. The monostable multivibrator allows current to flow for the short period of time required to change the position of an armature pivotably coupled to the electromagnet. After the flip-flop subsequently receives two pulses from the rate divider, its Q output goes negative and the Q output becomes positive. This allows another monostable multivibrator to provide a brief pulse of current, in the opposite direction, to the electromagnet to return the armature to the first position. The fluid in the casette may thus flow to the patient.