Smiths Medical Medfusion 3000 Series, Technical & Service Manual

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Theory of Operation
27 40-5648-51B
Section 2: Theory of Operation of the manual con -
tains definitions and descriptions of standard opera -
tion of the Medfusion™ 3000 Series pumps.
Overview of operation
The Medfusion™ 3000 Series pump design allows the
precise control of the infusion rates over a wide range
of syringe sizes and manufacturers as specified in the
Operation Manual.
Controlling motor functions
A stepper motor driving the plunger driver controls
the infusion rate. The motor receives electrical pulses
from microcontroller with pulse frequency deter -
mined from the programmed flow rate.
• Forty-eight motor pulses turn the motor one full
revolution.
• Five hundred and sixty full motor revolutions
move the plunger driver one inch.
• Therefore, 26,880 motor steps move the plunger
driver 1 inch (or 0.000037 inches per motor step)
−
providing very good flow continuity and precise
delivery.
Infusion control & safety
functions
Two sensors are used to verify that the infusion pro -
ceeds at the programmed rate. Specifically, the micro-
controller uses:
a) the motor rotation sensor to verify proper motor
speed;
b) the position sensor to verify proper syringe plunger
driver motion over time.
If the microcontroller determines either motor or sy -
ringe plunger driver is running at a speed not equiva -
lent to the programmed flow rate, then the infusion
stops and a system fault alarm warns the user.
Four additional sensors verify the syringe parameters:
a) The plunger sensor, in the head of the plunger
driver, detects proper engagement of syringe
plunger with syringe plunger driver.
b) The flange clip detects the proper position of the
syringe flange.
c) The syringe barrel clamp detects both
syringe pres-
ence and syringe size .
d) A force sensor in the plunger driver head detects
and reports the amount of force exerted on syringe
plunger head. A large amount of force indicates
an occlusion in the patient line to the microcon-
troller.
A Watchdog device checks for microcontroller mal -
function including timebase errors, and can shutdown
the motor and generate an alarm independent of the
microcontroller operation. An internal power source
( i.e., 1 Farad super-capacitor) allows the pump to
alarm should failure occur in the pump’s power sys -
tem or internal battery.