Nibp Module, Linear Bleed - Datascope Accutorr Plus Service Manual

Power ON Tone
The power on tone is used to inform the user the unit is powered on. The speakers
amplifier is driven by an oscillator for a min. 70 mS. The device is triggered by either a
press of the ON/STBY key, turning the unit on, or a reset condition. The oscillator is
designed to run at approximately 600hz.
Central Station
The microcontroller has control over the external serial communications with CSTAT*
and RS232ENB*. The board includes a connector, shared with the RS232, for connection to
an interface PCB. This interface includes RD, TD, RTS, and CTS for communication,
VBULK which is the main battery voltage, VCC for logic drive, CSTAT* for control of
the interface status and DGND. VBULK is capable of supplying 1 watt of power to this
module.

2.2.2 NIBP Module, Linear Bleed

Overview
The NIBP module contains only the Pneumatic and the Analog circuits. The NIBP
module is controlled by the CPU on the LED/CPU module. All analog signals are
converted by an on board serial A/D converter and sent serially to the CPU for processing.
The NIBP module, in conjunction with the LED/CPU module, measures the blood
pressure non-invasively using an inflatable cuff and the oscillometric principle.
The NIBP module is controlled by the CPU where it inflates the cuff, bleeds down the
cuff pressure during measurement and engages the dump valve which relieves cuff pressure
at the conclusion of the measurement. It monitors the air pressure in the cuff via a pressure
transducer. It is from this signal (both AC and DC components) that it determines the
NIBP of the patient via the oscillometric principle. Safety features include a hardware over
pressure limit set to the corresponding limit depending on patient size selected via the
control panel. This hardware pressure limit is in addition to a software controlled limit
which will provide redundant fail safe operation upon a fault condition.
The "Linear Bleed" NIBP module has a single proportional valve, having a continuously
variable effective orifice size. This valve is controlled by a servo loop, such that the cuff
deflation rate is closely and automatically regulated to a specified value, despite changes in
the cuff volume and pressure.
In addition, the NIBP module distributes the power from the power supply, which
includes power and control signals to the LED/CPU module. Via the LED/CPU board,
power is distributed to the rest of the system, such as the Recorder and the SpO
modules. Also, the NIBP module supplies separate power and control to: a) Pump filter
board, which powers the NIBP pump. b) LCD back light converter.
Accutorr Plus Service Manual
Chapter 2 - Theory of Operation
2
Revised 12/20/00
2-17