User Interface Pcb (Uif) - Mallinckrodt NELLCOR NPB-195 Service Manual

11.8 USER INTERFACE PCB (UIF)

11.8.1 Regulated DC Power Supply
11.8.2 Controlling Hardware
11.8.2.1 CPU
The 331 CPU on the UIF PCB monitors the charge level of the battery. If the
voltage of the battery falls below 5.85 ± 0.1 VDC, a low battery alarm is
declared. The instrument will continue monitoring and alarming for 15 minutes
then power down. This 15-minute alarm and power-down sequence can be
repeated by turning the unit back on, provided the battery voltage remains above
the critical level.
Battery voltage is considered critical when it decreases to 5.67 ± 0.1 DCV. If the
instrument is turned on and battery voltage is at the critical level, an error code is
displayed and the instrument will not monitor the patient. The instrument will
run for 15 minutes with the error code displayed and then power down.
Both conditions can be corrected by plugging the unit into an AC source for 14
hours to allow the battery to fully recharge.
The UIF PCB is the heart of the NPB-195. All functions except the unregulated
DC power supply, LCD display and membrane keypad reside on the UIF PCB.
The UIF PCB receives the Main_DC unregulated voltage of 7 to 18 VDC from
the Power Supply or 5.8 to 6.5 VDC from the internal battery. From either of
these signals, the regulated power supply on the UIF PCB generates +10.0,
-10.0, -5.0 and +5.0 VDC.
Two microprocessors reside on the UIF PCB. The CPU is an MC68331CF
(331). The CPU controls the second microprocessor, an Intel 80C196KC (196).
The 331 is the main controller of the NPB-195. The 331 controls the front panel
display, data storage, instrument status, serial port communication, and nurse
call. The 331 monitors all buttons on the user interface.
The user interface includes the front panel display and the keypad. By pressing
any of the keys on the keypad, the operator can access different functions of the
NPB-195. The 331 will recognize the keystroke and make the appropriate
change to the monitor. Some of the changes operators can make include the
view on the LCD display, alarm limits, and alarm volume. SECTION 4: of this
manual goes into more detail about the use of the softkeys.
Patient data is stored by the NPB-195 and can be downloaded to a printer
through the serial port provided on the back of the instrument. An in-depth
discussion of the serial port is covered in the Section 10 of this manual.
Power to the NPB-195 is monitored by the 331, which will determine if the
instrument is running on AC, or on battery power. If the monitor is running on
AC power, the 331 will periodically turn off the battery charge circuit to check
the battery charge level.
Section 11: Technical Supplement
11-5