Smiths Graseby 3200, Technical & Service Manual

Page: 40 / 117

Smiths Medical International Ltd.
Issue 5 (August 2004)
3200 Service Manual 3 — 3
The above action causes a voltage proportional to the pressure in the infusion line to be
input to one of the channels of the 8 bit A-to-D converter in the micro-controller.
If the output from the A-to-D converter exceeds the predetermined value set by the user,
an in-line occlusion alarm is generated.
The presence of a pressure sensing disc on the pump is confirmed by an opto-sensor
which is located at the bottom of the sensor housing. If the sensor detects that the sens-
ing disc has been removed during an infusion, an alarm is generated.
Electro/mech control system
Electro/mech control system
The microprocessor provides the pulse train for the stepper-motor to produce the set flow
rate. The rotation of the leadscrew slotted disc (see page 3-2, Internal occlusion system) is
monitored by the opto-sensor.
If the appropriate pulses are not detected by the opto-sensor, an alarm is generated.
The mechanical characteristics of the system are:
• motor step angle: 15 degrees
• gearbox reduction ratio: 210:1
• number of motor 5,040 at all times
steps per revolution
of leadscrew:
• leadscrew pitch: 1.5 mm
• syringe characteristic: 1 ml/1.8 mm (BD 60 ml syringe)
Sensing (alarm) systems
In addition to the occlusion sensing system (page 3-2), the following sensing systems are
also operative within the pump.
A metal flag protrudes from the left hand side of the half nut in parallel with the leadscrew.
As the syringe plunger reaches the end of its travel, the flag de-activates opto-sensor OPT00
situated on the opto sensors board. When the microprocessor detects that this sensor is de-
activated and the slotted disc is no longer rotating, it generates an END OF INFUSION/EMPTY
alarm.
When the metal flag de-activates opto-sensor OPT00 and the slotted disc is still rotating the
microprocessor makes a calculation (dependent upon the infusion rate) and issues a NEARLY
EMPTY alarm three minutes before the end of the infusion.
The sensing system will detect an AC power failure.
The pump continues to run after an AC power failure for a period of 2.5 hours or more by
switching automatically to the pump’s internal (fully charged) batteries.
Introduction
End of infusion
Syringe nearly
empty
AC power
failure