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Medical fluid injector having watchdog circuit

  • US 6,254,572 B1
  • Filed: 11/22/1999
  • Issued: 07/03/2001
  • Est. Priority Date: 11/22/1996
  • Status: Expired due to Term
First Claim
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1. An injector for injecting fluids from a syringe into an animal subject, comprising:

  • a plunger drive ram, a motor for moving said plunger drive ram, a syringe mounting for attachment to a syringe to position a syringe relative to said injector to permit said plunger drive ram to engage and move a plunger into or out of said syringe, a hand-operated movement control for generating a movement request signal indicating movements of said plunger drive ram desired by an operator, an encoder connected to said motor for generating a motion signal indicative of motion of said plunger drive ram, a motor control circuit connected to said motor, said hand-operated movement control and said encoder controlling said motor to move said ram and plunger to inject fluid from said syringe, said motor control circuit being responsive to said movement request signal to instruct said motor to move said plunger drive ram, said motor control circuit further generating a state signal indicating a state of operation of said motor control circuit for delivery through a monitor interface of said motor control circuit, said state signal indicating at least whether said motor control circuit is responding to said movement request signal by moving said motor, a motor monitor circuit connected to said hand-operated movement control, said encoder, and said monitor interface of said motor control circuit, monitoring said movement request signal, said motion signal and said state signal, said motor monitor circuit confirming that said state signal is consistent with said movement request signal and said motion signal, by at least confirming that when said movement request signal indicates that movements of said motor are desired, and said state signal indicates said motor control circuit is responding to said movement request signal to move said motor, said motion signal indicates said motor is moving in accordance with said movement request signal.

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